MACLKSSM.DOC





				  MACREL/LINK
			    Software Support Manual

				  AA-J073A-TA
















				  DISCLAIMER

		This document file was created by scanning  the
		original  document and then editing the scanned
		text.  As much as possible, the  original  text
		format  was restored.  Some format changes were
		made to insure this  document  would  print  on
		current laser printers using 60 lines per page.
		The  original  spelling  and  grammar  has been
		preserved.


		1-Apr-1997




						     MACREL/LINK
						Software Support Manual

						     AA-J073A-TA













				September 1980

	This manual describes the internal data structures and processes
	of the MACREL Assembler and the LINK Linking Loader. Its purpose
	is to provide experienced users with the detailed technical
	information necessary to allow them to effectively maintain or
	modify these programs.


	This is a new document.

	OPERATING SYSTEM:				OS/8 Version 3D

	SOFTWARE: MACREL				Version 2C
							LINK Version 2AG
















     ----------------------------------------------------------------------
     | To order additional copies of this document, contact the Software  |
     | Distribution  Center,  Digital  Equipment  Corporation,   Maynard, |
     | Massachusetts 01754						  |
     ----------------------------------------------------------------------

	    digital equipment corporation - maynard, massachusetts








					     First Printing, September 1980


     The information in this document is subject to change  without  notice
     and  should  not  be  construed  as  a commitment by Digital Equipment
     Corporation.  Digital Equipment Corporation assumes no  responsibility
     for any errors that may appear in this document.

     The software described in this document is furnished under  a  license
     and  may  only  be used or copied in accordance with the terms of such
     license.

     No responsibility is assumed for the use or reliability of software on
     equipment that is not supplied by DIGITAL or its affiliated companies.






	     Copyright (c) 1980, by Digital Equipment Corporation.
			      All Rights Reserved.





     The postage-prepaid READER'S COMMENTS form on the last  page  of  this
     document  requests  the  user's  critical  evaluation  to assist us in
     preparing future documentation.

     The following are trademarks of Digital Equipment Corporation:

	  DEC		      DECnet		  IAS
	  DECUS		      DECsystem-10	  MASSBUS
	  Digital Logo	      DECSYSTEM-20	  PDT
	  PDP		      DECwriter		  RSTS
	  UNIBUS	      DIBOL		  RSX
	  VAX		      EduSystem		  VMS
						  VT










				    M10000





				   CONTENTS

								       Page

     PREFACE								xi

     PART     I	       MACREL

     CHAPTER  1	       INTRODUCTION				       1-1

	      1.1      SYSTEM LAYOUT				       1-1
	      1.1.1      Resident Code				       1-1
	      1.1.2	 Overlay Code				       1-2
	      1.2      IMPLEMENTATION LANGUAGE			       1-2
	      1.3      LABEL AND SYMBOL CONVENTIONS		       1-2
	      1.3.1	 Directive Routine Labels		       1-3
	      1.3.2	 Labels for Macro-Processing Modules	       1-3
	      1.3.3	 Global Symbol Definition File (MGLOB.MA)      1-3
	      1.3.4	 Labels for Commonly Used Routines and
			 Constants				       1-3
	      1.3.5      Local (Page) Symbols			       1-6
	      1.4      ROUTINE CALLING CONVENTIONS		       1-6
	      1.4.1      ERROR Routine Calls			       1-6
	      1.4.2	 Subprogram Interfaces and Calling Sequences   1-6
	      1.4.3	 Overlay Module Calling Conventions	       1-7
	      1.5      DATA FORMATS AND REPRESENTATIONS		       1-7
	      1.5.1	 Character Encoding and Packing Schemes	       1-8
	      1.5.2	 15-Bit Pointers			       1-8
	      1.5.3	 Chunks					       1-9
	      1.5.4	 Symbol Table Organization		       1-9
	      1.5.4.1    Character Codes for Symbol Table Entries      1-9
	      1.5.5	 Symbol Table Entry Formats		       1-9
	      1.5.5.1	 Regular Symbol Table Entry Format	       1-10
	      1.5.5.2	 .MACRO Symbol Table Entry Format	       1-12
	      1.5.5.3	 Pseudo-Operator and Pseudo-Macro Symbol
			 Table Entry Format			       1-12
	      1.5.5.4	 .EXTERNAL Symbol Table Entry Format	       1-13
	      1.5.5.5	 .ASECT Symbol Table Entry Format	       1-13
	      1.5.5.6	 .DSECT Symbol Table Entry Format	       1-14
	      1.5.5.7	 .RSECT Symbol Table Entry Format	       1-14
	      1.5.5.8	 .FSECT .XSECT and .ZSECT Symbol Table
			 Entry Format				       1-15
	      1.5.5.9	 Auxiliary Symbol Table Chunk Entry Format     1-15
	      1.6      TABLES, STACKS, AND BUFFERS		       1-16
	      1.7      DEFAULT CONDITIONS			       1-17
	      1.8      ERROR AND EXCEPTION REPORTING		       1-18

     CHAPTER  2	       DESCRIPTIONS OF THE MODULES		       2-1

	      2.1      EXPOVR (Overlay 32)			       2-2
	      2.1.1	 BACKL					       2-2
	      2.1.2	 IDIV					       2-4

				      iii



				   CONTENTS

								       Page

	      2.1.3	 IMUL					       2-4
	      2.1.4	 SNGLQQ					       2-5
	      2.1.5	 UPAROQ					       2-5
	      2.2      FIN0 (Overlay 10)			       2-7
	      2.2.1	 NEXTT					       2-7
	      2.2.2	 OPEN1					       2-8
	      2.2.3	 OPEN2					       2-8
	      2.2.4	 OPEN3					       2-8
	      2.2.5	 OPEN4					       2-10
	      2.2.6	 FIN5					       2-10
	      2.2.7	 AINIT					       2-11
	      2.2.8	 CPYTOC					       2-12
	      2.2.9	 REIT					       2-13
	      2.2.10	 IOINIT					       2-13
	      2.2.11	 IONIT2					       2-14
	      2.3      FIN2 (Overlays 12 and 14)		       2-14
	      2.3.1	 Unlabeled Routine			       2-14
	      2.3.2	 LSDOUT (Overlay 12)			       2-16
	      2.3.3	 ZPAD (Overlay 12)			       2-18
	      2.3.4	 LSDINI (Overlay 14)			       2-18
	      2.3.5	 FINIO (Macio)				       2-19
	      2 4      FIN3 (Overlays 11 and 13)		       2-20
	      2 4.1	 Unlabeled Routine (Overlay 11)		       2-20
	      2.4.2	 STPRNT (Overlay 11)			       2-22
	      2.4.3	 PRNT2 (Overlay 11)			       2-23
	      2.4.4	 PRN (Overlay 13)			       2-23
	      2.4.5	 XPRINT (Overlay 13)			       2-23
	      2.4.6	 PRNT6 (Overlay 13)			       2-25
	      2.5      MACERR (Special Overlay)			       2-25
	      2.5.1	 Error Typeout Routines			       2-26
	      2.5.2	 Creating New Error Messages		       2-27
	      2.5.3	 Number of Errors Detected		       2-29
	      2.6      MACEXP					       2-29
	      2.6.1	 EXPR					       2-29
	      2.6.2	 TERM					       2-31
	      2.7      MACINI					       2-33
	      2.7.1	 DATE					       2-33
	      2.7.2	 ONCE					       2-34
	      2.7.3	 CORE					       2-34
	      2.7.4	 LIMSET					       2-34
	      2.7.5	 PREFORM				       2-35
	      2.7.6	 SYMINI					       2-35
	      2.8      MACIO					       2-36
	      2.8.1	 IOINIT and IONIT2			       2-37
	      2.8.2	 FINIO (MACIO)				       2-37
	      2.8.3	 READOS					       2-37
	      2 8 4	 SWITCH					       2-38
	      2 8 5	 SWBACK					       2-39
	      2.8.6	 GETOS and ORET Coroutines		       2-39
	      2.8.7	 MGET and RGET Coroutines		       2-40

				      iv



				   CONTENTS

								       Page

	      2.8.8	 ZGET					       2-40
	      2.8.9	 OFIX					       2-40
	      2.8.10	 SPUSH					       2-40
	      2.8.11	 SPOP					       2-41
	      2.8.12	 LOCPSH					       2-42
	      2.8.13	 LOCPOP					       2-42
	      2.8.14	 OFETCH					       2-42
	      2.8.15	 PUTBUF					       2-42
	      2.8.16	 LISTOR, LSTRET, and OUTLST		       2-42
	      2.8.17	 CONV					       2-42
	      2.8.18	 DELETE					       2-42
	      2.8.19	 LOOKU					       2-43
	      2.8.20	 ZINIT					       2-43
	      2.9      MACLIT (Overlay 31)			       2-43
	      2.9.1	 ZSECTG					       2-43
	      2.9.2	 ZL					       2-44
	      2.9.3	 GENUN					       2-44
	      2.9.4	 ZLIT					       2-44
	      2.9.5	 PRGSPL					       2-45
	      2.9.6	 KLU10					       2-45
	      2.9.7	 PURGEL					       2-45
	      2.9.8	 OUTLIT					       2-45
	      2.9.9	 CMNMOV					       2-46
	      2.10     MACMAC (Overlays 26, 27, and 30)		       2-47
	      2.10.1	 $MACRO					       2-47
	      2.10.2	 PART2					       2-47
	      2.10.3	 $REPT					       2-47
	      2.10.4	 MC					       2-48
	      2.10.5	 $MEXIT					       2-48
	      2.11     MACOPN (Overlay 33)			       2-48
	      2.11.1	 OPEN					       2-48
	      2.11.2	 OPENTC					       2-49
	      2.11.3	 OFETCH					       2-49
	      2.12     MACORG (Overlay 7)			       2-49
	      2.13     MACRO					       2-49
	      2.14     MACRTH (Overlay 6)			       2-51
	      2.15     MACTBL					       2-52
	      2.16     MAC2					       2-52
	      2.16.1	 PUXBIN					       2-53
	      2.16.2	 BPUT					       2-53
	      2.16.3	 PUNBIT					       2-53
	      2.16.4	 PUTBIT					       2-54
	      2.16.5	 ORIG					       2-54
	      2.16.6	 PUTB					       2-54
	      2.16.7	 PUNY					       2-54
	      2.16.8	 PUTLC					       2-54
	      2.16.9	 UNNAM					       2-54
	      2.17     MAC24					       2-55
	      2.17.1	 NEX					       2-55
	      2.17.2	 GETLSD					       2-55

				       v



				   CONTENTS

								       Page

	      2.17.3	 IGNORE					       2-55
	      2.17.4	 CNVADR					       2-55
	      2.17.5	 $PAUSE					       2-55
	      2.17.6	 HGHSCT					       2-56
	      2.17.7	 LOAD					       2-57
	      2.17.8	 SETIT					       2-57
	      2.17.9	 PRZLIT					       2-57
	      2.17.10	 PRGLIT					       2-57
	      2.17.11	 BACKSL					       2-57
	      2.17.12	 ERROR					       2-57
	      2.17.13	 NEXTCHAR				       2-58
	      2.17.14	 GETSYM					       2-58
	      2.17.15	 PUTSYM					       2-58
	      2.17.16	 READLN					       2-59
	      2.17.17	 $FIXMRI				       2-59
	      2.17.18	 EQL					       2-60
	      2.17.19	 GETCHR					       2-60
	      2.17.20	 SCAN					       2-60
	      2.17.21	 GET					       2-60
	      2.17.22	 CTRLC					       2-60
	      2.17.23	 FINI					       2-60
	      2.17.24	 BACKUP					       2-60
	      2.17.25	 BRAN					       2-61
	      2.17.26	 NUMLCL					       2-61
	      2.17.27	 BRANCH					       2-61
	      2.17.28	 ASEMBL					       2-62
	      2.17.29	 GETEX					       2-62
	      2.17.30	 ASEMLV					       2-62
	      2.17.31	 OUTDATA				       2-62
	      2.17.32	 TAGCOM					       2-62
	      2.17.33	 TAGCOL					       2-62
	      2.17.34	 ORIGIN					       2-62
	      2.17.35	 LETTER					       2-63
	      2.17.36	 TSTMAC					       2-63
	      2.17.37	 DIGIT					       2-63
	      2.17.38	 ROTL6					       2-63
	      2.17.39	 PARSYM					       2-63
	      2.17.40	 EOS					       2-64
	      2.17.41	 LOOP					       2-64
	      2.17.42	 CALLIT					       2-64
	      2.17.43	 GETKAR					       2-65
	      2.17.44	 PUSH					       2-65
	      2.17.45	 POP					       2-65
	      2.17.46	 LOOKUP					       2-65
	      2.17.47	 CREF					       2-65
	      2.17.48	 ENTER					       2-66
	      2.17.49	 KLU4					       2-66
	      2.18     MAC30 (Overlay 15)			       2-66
	      2.18.1	 PRINTY					       2-66
	      2.18.2	 PRLINO (MAC2)				       2-66

				      vi



				   CONTENTS

								       Page

	      2.18.3	 SETT					       2-67
	      2.18.4	 DPRINT					       2-67
	      2.18.5	 OPRINT					       2-67
	      2.18.6	 NPRINT					       2-67
	      2.18.7	 CRLF					       2-67
	      2.18.8	 LIST					       2-68
	      2.18.9	 PRNDSH					       2-68
	      2.18.10	 PRNBIN					       2-68
	      2.18.11	 TAB					       2-68
	      2.19     MAC3R					       2-68
	      2.19.1	 OUT					       2-68
	      2.19.2	 NEWPAG					       2-69
	      2.19.3	 LISTER					       2-70
	      2.19.4	 OVRLIN					       2-70
	      2.19.5	 PASS3					       2-70
	      2.20     OVRA (Overlay 1)				       2-70
	      2.20.1	 $PAGE					       2-71
	      2.20.2	 $ZBLOCK				       2-71
	      2.20.3	 $TEXT					       2-71
	      2.21     OVRB (Overlay 2)				       2-72
	      2.21.1	 $IFNZRO				       2-72
	      2.21.2	 $IFZERO				       2-73
	      2.21.3	 $IFDEF					       2-73
	      2.21.4	 $IFNDEF				       2-73
	      2.21.5	 $IF					       2-73
	      2.22     OVRC (Overlay 3)				       2-74
	      2.22.1	 TASKY					       2-74
	      2.22.2	 $OCTAL					       2-75
	      2.22.3	 $DECIMA				       2-75
	      2.22.4	 $RADIX					       2-75
	      2.22.5	 $FILENA				       2-75
	      2.22.6	 $DEVICE				       2-76
	      2.22.7	 $ENABLE				       2-76
	      2.22.8	 $DISABL				       2-78
	      2.23     OVRD (Overlays 4 and 35)			       2-78
	      2.24     OVRE (Overlay 5)				       2-79
	      2.24.1	 $CHAIN					       2-79
	      2.24.2	 $INCLUD				       2-79
	      2.24.3	 $ENTRY					       2-80
	      2.24.4	 $EXTERN				       2-80
	      2.24.5	 $ZTRNA					       2-80
	      2.24.6	 $GLOBAL				       2-80
	      2.24.7	 GLOB2					       2-80
	      2.25     OVRQ (Overlays 21 and 34)		       2-81
	      2.25.1	 BLKLET					       2-81
	      2.25.2	 OUTBLK					       2-81
	      2.25.3	 BINFO					       2-82
	      2.26     OVRR (Overlay 22)			       2-82
	      2.26.1	 $XLIST					       2-82
	      2.26.2	 PREFIN					       2-82

				      vii



				   CONTENTS

								       Page

	      2.26.3	 $NOPUNC				       2-83
	      2.26.4	 $ENPUNC				       2-83
	      2.26.5	 $JSW, $VERSIO, and $START		       2-83
	      2.26.6	 $NOLIST and $LIST			       2-83
	      2.27     OVRS (Overlay 23)			       2-84
	      2.27.1	 $FIXTAB				       2-84
	      2.27.2	 $EXPUNGE				       2-84
	      2.28     OVRT (Overlay 24)			       2-84
	      2.28.1	 LNKCHN					       2-84
	      2.28.2	 KRFCHN					       2-85
	      2.28.3	 $FIELD					       2-85
	      2.29     OVRU (Overlay 25)			       2-85
	      2.29.1	 $SBTTL					       2-85
	      2.29.2	 $EJECT					       2-85
	      2.29.3	 $TITLE					       2-86
	      2.29.4	 $RELOC					       2-86
	      2.29.5	 $PUSH and $POP				       2-86
	      2.30     PAS2 (Overlay 16)			       2-86
	      2.30.1	 PUTBN					       2-87
	      2.30.2	 CHKFUL					       2-87
	      2.30.3	 PUTBT					       2-87
	      2.30.4	 GETFLG					       2-88
	      2.30.5	 BPUTX					       2-88
	      2.30.6	 CREFX					       2-88
	      2.30.7	 MORCRF					       2-88


























				     viii



				   CONTENTS

								       Page


     PART     II       LINK

     Chapter  3	       INTRODUCTION				       3-1

	      3.1      INTRODUCTION				       3-1
	      3.2      SYSTEM LAYOUT				       3-1
	      3.3      IMPLEMENTATION LANGUAGE			       3-1
	      3.4      LABEL AND SYMBOL CONVENTIONS		       3-1
	      3.5      ROUTINE CALLING CONVENTIONS		       3-2
	      3.6      DATA FORMATS AND REPRESENTATIONS		       3-2
	      3.7      TABLES					       3-2
	      3.7.1	 Global Symbol Table (GST)		       3-2
	      3.7.2	 Binary Buffer Table (LDBUFS)		       3-4
	      3.7.3	 Pointer Table (PTRTAB)			       3-5
	      3.7.4	 Module Descriptor Table (MODTAB)	       3-5
	      3.7.5	 .SECT Table (SECTAB)			       3-5
	      3.7.6	 Core Image Table (CIMAG, CIMAGl, CIMAG2,
			 and CIMAGE)				       3-8
	      3.7.7	 Overlay Transfer Vector (TRANVC)	       3-8
	      3.7.8	 User Overlay Level Data Table (QUSRLV)	       3-9
	      3.7.9	 Overlay Level Information Table (LHDR)	       3-10
	      3.7.10	 Main Binary Section Table (MBST)	       3-10
	      3.7.11	 Memory Segment Control Double Words	       3-12
	      3.7.12	 Library Table (LIBTB)			       3-12
	      3.8      DEFAULT CONDITIONS			       3-12
	      3.9      LINK ERROR AND EXCEPTION REPORTING	       3-14

     CHAPTER  4	       DESCRIPTIONS OF THE MODULES		       4-1

	      4.1      LNKALL					       4-1
	      4.2      LNKBN1 AND LNKBN2			       4-3
	      4.3      LNKCAL					       4_4
	      4.4      LNKCD					       4-5
	      4.5      LNKMAN					       4-5
	      4.6      LNKLSD					       4-8
	      4.7      LNKMSG					       4-10
	      4.8      LNKMAP					       4-10

     APPENDIX A	       CHARACTER SETS				       A-1

     APPENDIX B	       MACREL MAINTENANCE PROCEDURES		       B-1

     APPENDIX C	       SUMMARY OF MACREL'S MAJOR MODULES	       C-1

     APPENDIX D	       BATCH FILES FOR ASSEMBLING AND LINKING MACREL,
		       LINK, AND KREF				       D-1

     APPENDIX E	       MEMORY UTILIZATION AND MODULE SUMMARY	       E-1


				      ix



				   CONTENTS

								       Page

     APPENDIX F	       MACREL COMMAND DECODER OPTIONS		       F-1

     APPENDIX G	       DISCUSSION OF SELECTED ROUTINES IN LINK	       G-1

	      G.1      ADJPTR (LNKLSD)				       G-1
	      G.2      ALLOC (LNKALL)				       G-1
	      G.3      BULDTV (LNKBN2)				       G-1
	      G.4      CPIC (LNKALL)				       G-2
	      G.5      NEWBB (LNKBN2)				       G-2
	      G.6      NEWORG (LNKBN2)				       G-2
	      G.7      PUTBIN (LNKBN2)				       G-2
	      G.8      RELOCA (LNKBN2)				       G-2
	      G.9      SEARCH (LNKMAN)				       G-3
	      G.10     SSORT (LNKALL, LNKLSD, and LNKMAP)	       G-3

     INDEX							   Index-1




				    FIGURES

     FIGURE   1-1      OS/8 ASCII Character Packing		       1-8
	      1-2      15-Bit Pointer Format			       1-9
	      2-1      Memory Limit Table (LIMTBL) Layout	       2-35
	      2-2      Formal Argument Table Entry Format	       2-47
	      2-3      Actual (macro) Argument Table Layout	       2-51
	      3-1      Main Binary Section Table Layout		       3-11
	      3-2      Library Table Layout			       3-13
	      D-1      BATCH File for Building MACREL, LINK, and
		       KREF					       D-2




					   TABLES

     TABLE    1-1      Summary of Commonly Used Resident (Field 0)
		       Routines					       1-4
	      1-2      Symbol Table Flag Word			       1-10
	      1-3      Format for Regular Symbol Table Entries	       1-11
	      1-4      Format for Regular Symbol Table Entries with
		       Extended Names				       1-11
	      1-5      Extended Symbol Name Field Definitions	       1-12
	      1-6      Format for .MACRO Symbol Table Entries	       1-12
	      1-7      Format for Pseudo-Operators (PSEUD) and
		       Pseudo-Macros (PSEUM) Symbol Table Entries      1-13
	      1-8      Format for .EXTERNAL Symbol Table Entries       1-13
	      1-9      Format for .ASECT Symbol Table Entries	       1-14
	      1-10     Format for .DSECT Symbol Table Entries	       1-14

				       x



				   CONTENTS

								       Page

	      1-11     Format for .RSECT Symbol Table Entries	       1-15
	      1-12     Format for .XSECT, .ZSECT, and .FSECT
		       Symbol Table Entries			       1-15
	      1-13     Symbol Table Layout for Auxiliary Chunks
		       (.SECTs only)				       1-16
	      1-14     Summary of Tables, Stacks, and Buffers	       1-17
	      2-1      MACREL Module Summary			       2-1
	      2-2      Basic Letter Block Widths vs Listing Device
		       Column Width				       2-9
	      2-3      LSD Entry Type Codes			       2-17
	      2-4      Loader Symbol Dictionary Entry Types,
		       Destinations, and Tasks			       2-24
	      2-5      Layout of MACERR Within MACREL.SV	       2-26
	      2-6      MACERR Output Routine Summary		       2-26
	      2-7      Local Variables Saved on the Expression Stack   2-30
	      2-8      EXPR Previous Operator Dispatch Table	       2-31
	      2-9      TERM Character Dispatch Table		       2-31
	      2-10     Internal Storage Format of OS/8 Date Words      2-33
	      2-11     Initial Symbol Table Entry Format	       2-36
	      2-12     Symbol Table Flags Definitions		       2-40
	      2-13     Summary of Routines in the MACRO Module	       2-50
	      2-14     Descriptions of MACRTH Routines		       2-51
	      2-15     Character Branch Table (MACTBL) Classification
		       Codes					       2-53
	      2-16     Assembly Listing Symbol Name Qualifiers	       2-66
	      2-17     TEXT Directive Coroutines		       2-72
	      2-18     .IF Directive Conditions			       2-74
	      2-19     $ENABLE Condition Options		       2-76
	      2-20     $DISABL Condition Options		       2-78
	      2-21     OVRD Entry Points and CST Values		       2-78
	      3-1      Global Symbol Table Entry Format		       3-3
	      3-2      Global Symbol Table Symbol Type Codes	       3-4
	      3-3      Number of Binary Buffers as a Function of
		       Memory Size				       3-5
	      3-4      Module Descriptor Table Format		       3-6
	      3-5      .SECT Table Format			       3-6
	      3-6      Core Image Table Format			       3-8
	      3-7      Overlay Transfer Vector Format		       3-9
	      3-8      Overlay Level Data Table Format		       3-10
	      3-9      Overlay Information Table Entry Format	       3-10
	      3-10     Memory Segment Control Double Word Entry
		       Format					       3-12
	      4-1      Routines in LNKMAN			       4-6
	      A-1      MACREL Special 6-bit Character Codes	       A-1
	      A-2      ASCII Character Set			       A-1
	      E-1      MACREL Memory Utilization		       E-1
	      E-2      Overlay Module Data Summary		       E-4




				      xi






				    PREFACE


     ABOUT THIS MANUAL

     The MACREL/LINK Software Support Manual describes  the  internal  data     _______________________________________
     structures  and processes of the MACREL Assembler and the LINK Linking
     Loader.  Its purpose is to provide experienced users with the detailed
     technical  information necessary to allow them to effectively maintain
     or modify these programs.

     To use this manual effectively, you must be completely  familiar  with
     PDP/8  computer  hardware  and  macro  assembler programming using the
     MACREL and LINK programs.   You should  also  be  familiar  with  OS/8
     system operation and OS/8 terminology.

     The manual is designed for use in  conjunction  with  the  MACREL/LINK								___________
     User's  Manual  and the MACREL and LINK assembly listings.  Though the     ______________
     listings are well commented, but some of the comments may be obsolete.
     If  there  is a conflict between the listing comments and this manual,
     this manual takes precedence.

     The manual is divided into two parts: Part 1, MACREL; Part 2, LINK.



     SYNOPSIS

     Chapter 1 introduces the MACREL assembler and describes  its  internal
     structure and conventions.

     Chapter 2 consists of detailed descriptions of the major  routines  in
     each  of MACREL's source modules.  The chapter presents the modules in
     alphabetical order by module name.

     Chapter 3  introduces  the  LINK  linking  loader  and  describes  its
     internal structure and conventions.

     Chapter  4  consists  of  functional  descriptions  of  LINK's  source
     modules.   The  chapter  presents the modules in alphabetical order by
     module name.

     The appendixes contain MACREL  and  LINK  batch  assembly  procedures,
     MACREL   maintenance  procedures,  summary  descriptions  of  MACREL's
     overlays and major routines, character codes.







				      xii



     REFERENCES TO DOCUMENTS

     The  text  of  this  manual  contains  references  to  the   following
     documents:

	  MACREL/LINK User's Manual (AA-5664A-TA)	  _________________________

	  OS/8 Language Reference Manual (PAL8 section) (AA-H609A-TA)	  ______________________________

	  MACREL and LINK Assembly Listings (contained in files residing on	  _________________________________
	  DECtapes:     AL-5643B-SA    (MACREL);    AL-5644B-SA   (MACREL);
	  AL-H602B-SA (LINK);  AL-H603B-SA (LINK)



     DOCUMENT CONVENTIONS

     This section describes the  conventions  and  symbology  used  in  the
     manual.

	  o  Fully capitalized words in the text are the  names  of  either
	     source modules, routines, entry points, or variables.

	  o  References to  routines,  entry  points,  and  variables  that
	     reside  in  a  module  other  than the one being discussed are
	     followed by the module  name  enclosed  in  parentheses.   For
	     example,  in the discussion of the PAS2 module, a reference to
	     the QPUT routine in module MACIO would appear as:

	     ...  text ...  QPUT (MACIO) ...  text ...

























				     xiii





























				    PART I

				    MACREL






				   CHAPTER 1

				 INTRODUCTION


     MACREL is a four-pass assembler.  Pass 1 defines all the  symbols  and
     creates the table-of-contents.  Pass 2 creates the binary output file.
     Pass 3 creates the listing file.  Pass 4 creates the data file used by
     the KREF program to generate a cross-reference listing.  Four separate
     passes are necessary because the OS/8 operating system does not permit
     more than one output file to be open on the same device.

     MACREL accepts input from various sources called input streams,  which
     may  be internal or external.  The main input stream is the OS/8 input
     file that contains the user's  source  program.   MACREL  switches  to
     other input streams in response to the following directives and macros
     in the source file:

	  o  The .CHAIN directive permanently switches the input stream  to
	     another, external, OS/8 input file.

	  o  The .INCLUDE directive temporarily switches the  input  stream
	     to another, external, OS/8 input file.

	  o  A macro invocation switches the input stream  to  an  internal
	     source called the macro input stream.

	  o  The real arguments to a macro switch the input  stream  to  an
	     internal source called the argument input stream.

	  o  The .REPT directive switches the input stream to  an  internal
	     source called the repeat input stream.

     The streams are controlled by a switching control  routine  and  input
     coroutines.   The  switching  control routine uses a software pushdown
     stack to preserve the entire state of a coroutine so that input can be
     switched from one routine to another and back without loss of context.
     The input coroutines fetch characters from their associated sources.



     1.1  SYSTEM LAYOUT

     The following  paragraphs  describe  the  memory  layout  of  MACREL's
     resident  and  overlay  code.  Table E-1 (Appendix E) shows the memory
     allocation for each MACREL module.



     1.1.1  Resident Code


				      1-1
				 INTRODUCTION


     MACREL's resident code consists of seven modules:  MAC2, MAC24, MAC3R,
     MACEXP, MACIO, MACRO and MACTBL.  MAC24 is the main module and resides
     in Field 0.  It contains the assembler's main processing  loop,  which
     issues calls to all other modules.



     1.1.2  Overlay Code

     MACREL's overlay code consists of 28 modules (see Appendix E).  During
     execution these modules reside in one of four primary overlay areas:

	  1.  Directives Overlay Area.  Contains the overlays that  process
	      MACREL's directives.

	  2.  Pass Specific Overlay Area.  Contains the overlays  that  are
	      functionally related to the current assembly pass.

	  3.  Auxiliary Overlay Area.  Contains extension overlays  to  the
	      overlays  that  cannot  reside completely in one of the other
	      overlay areas.


				     NOTE

			When this area is not  used  to  contain
			overlay           extensions          to
			directive-processing    routines,     it
			contains   the   overlays  that  process
			little-used  expression  constructs  and
			complex  relocatable expressions.  It is
			important   to   note   therefore   that
			overlays   that   call   the  expression
			processor (MACEXP) must  not  load  code
			into this area.


	  4.  Extremities Overlay Area.   Contains  overlays  that  perform
	      end-of-pass  processing  (FIN  code)  and  start-of-next-pass
	      initialization code.  During specific passes,  this  area  is
	      the input buffer (INPBUF).



     1.2  IMPLEMENTATION LANGUAGE

     MACREL is coded in itself.  Since it is written to run  on  all  PDP-8
     processors, it does not use the MQ register.



     1.3  LABEL AND SYMBOL CONVENTIONS



				      1-2
				 INTRODUCTION


     1.3.1  Directive Routine Labels

     Labels for entry points to routines  that  implement  MACREL  language
     directives  begin  with  a dollar sign ($) followed by the name of the
     directive.   For  example,  the  routine  that  implements  the   PAGE
     directive is labeled $PAGE.

     A period (.) is not included in the label for a directive that  has  a
     leading period in its name.  For example, the code that implements the
     .CHAIN directive is labeled $CHAIN.  Only  the  first  (leftmost)  six
     characters  of  a  MACREL symbol, excluding a leading dollar sign ($),
     are significant.   Thus,  the  labels  for  the  directive  processing
     routines  may  not exactly match their directive keyword counterparts.
     For example, the routine that  implements  the  DECIMAL  directive  is
     labeled $DECIMA.



     1.3.2  Labels for Macro-Processing Modules

     Many of  the  modules  related  to  processing  of  macros  and  their
     arguments  have  labels consisting of one or two letters and a number.
     These numbers correspond to the step numbers given in comments at  the
     beginning of the module.



     1.3.3  Global Symbol Definition File (MGLOB.MA)

     The global symbol definition file is a parameter file that consists of
     global  symbol  definitions.   The  symbols  are referenced by a large
     number of MACREL's source  modules.   The  beginning  of  each  source
     module  contains  an .INCLUDE MGLOB.MA directive to make sure that the
     assembler reads the symbol definitions  before  assembling  a  module.
     The  file  establishes the common symbolic linkages between the source
     modules.  When assembling a module, you must be sure  that  this  file
     resides on the OS/8 device assigned to DSK:.


				    CAUTION

		    Do not change  the  value  of  a  global
		    symbol  by  redefining  it in one of the
		    modules.  You must make  the  change  in
		    MGLOB.MA  and  then  reassemble  all the
		    MACREL source modules  to  complete  the
		    process.



     1.3.4  Labels for Commonly Used Routines and Constants

     Labels to commonly used routines prefixed with the letters QQ are part
     of  the  Field 0 resident code and are transfer vectors.  For example,

				      1-3
				 INTRODUCTION


     JMS I QQENTER is a subroutine call to the ENTER routine  that  resides
     in Field 0 in the MAC24 module.  Table 1-1 contains a summary of these
     routines.  Commonly used constants  may  use  either  a  QQ  (positive
     constant)  or  QM  (minus constant) prefix.  For example, QQ177 is the
     constant 177, while QM10 is the constant -10 (7770).


				   Table 1-1
	     Summary of Commonly Used Resident (Field 0) Routines

     ----------------------------------------------------------------------
     | Name		|		Function			  |
     |------------------|-------------------------------------------------|
     | ASEMLV		| Sends the currently assembled statement to  the |
     |			| binary file.					  |
     |			|						  |
     | BACKUP		| Moves the line buffer pointer (LINPTR) back one |
     |			| position.					  |
     |			|						  |
     | BRAN		| Performs an indexed  branch  into  a  table  of |
     |			| addresses, and branches to the selected address.|
     |			|						  |
     | CREF		| Sends  the  symbol   name   and   line   number |
     |			| information to the cross reference (KREF) file. |
     |			|						  |
     | CRLF		| Sends a carriage return /line feed sequence  to |
     |			| the listing file.				  |
     |			|						  |
     | DPRINT		| Sends the decimal  number  in  the  accumulator |
     |			| (AC) to the number-printing routine NPRINT.	  |
     |			|						  |
     | ENTER		| Enters a symbol in the symbol table  when  that |
     |			| symbol  is  specified  in the symbol table work |
     |			| area.						  |
     |			|						  |
     | EOS		| Determines whether  the  current  character  in |
     |			| BITS is a statement delimiter.		  |
     |			|						  |
     | ERROR		| Calls the error message processor to  print  an |
     |			| error message.				  |
     |			|						  |
     | EXPR		| Parses a term and returns the absolute part  of |
     |			| the  result  in  the  accumulator  (AC) and the |
     |			| relative part in EXPREL.			  |
     |			|						  |
     | GETCHR		| Obtains a character from the  line  buffer  and |
     |			| determines its type code.			  |
     |			|						  |
     | GETKAR		| Obtains a character from the line buffer.	  |
     |			|						  |
     | GETSYM		| Loads a copy of a symbol table entry  into  the |
     |			| symbol table work area.			  |
     ----------------------------------------------------------------------
						(continued on next page)

				      1-4
				 INTRODUCTION


			      Table 1-1  (Cont.)
	     Summary of Commonly Used Resident (Field 0) Routines

     ----------------------------------------------------------------------
     | Name		|		Function			  |
     |------------------|-------------------------------------------------|
     | HGHSCT		| Obtains the highest address used by  a  program |
     |			| section.					  |
     |			|						  |
     | LETTER		| Determines if the current character  (CHAR)  is |
     |			| an  upper-case  or  lower-case letter, a period |
     |			| (.) or a dollar sign ($).			  |
     |			|						  |
     | LISTER		| Sends characters to the listing file.		  |
     |			|						  |
     | LOOKUP		| Searches the symbol table for a symbol.	  |
     |			|						  |
     | OPRINT		| Sends the octal number in the accumulator  (AC) |
     |			| to the number-printing routine NPRINT.	  |
     |			|						  |
     | ORIG		| Sets up the flag word (FLG)  and  sends  a  new |
     |			| location counter (PC) value to the binary file. |
     |			|						  |
     | OUT		| Sends a line to the listing file.		  |
     |			|						  |
     | PARSYM		| Parses a symbol from the current input stream.  |
     |			|						  |
     | PASS3		| Determines if a pass is pass 3.		  |
     |			|						  |
     | POP		| Removes (pops)  a  value  from  the  expression |
     |			| stack and leaves it in the accumulator (AC).	  |
     |			|						  |
     | PUNBIT		| Sends a binary entry and its flag field to  the |
     |			| binary  file;   prints  the current line during |
     |			| Pass 3.					  |
     |			|						  |
     | PUSH		| Places (pushes) the contents of the accumulator |
     |			| (AC) on the expression stack.			  |
     |			|						  |
     | PUTBIT		| Sends a binary entry without a  flag  field  to |
     |			| the binary file during pass 2.		  |
     |			|						  |
     | PUTSYM		| Inserts the data in the symbol table work  area |
     |			| into to the symbol table.			  |
     |			|						  |
     | PUXBIN		| Sends a binary entry and its flag field to  the |
     |			| binary file.					  |
     |			|						  |
     | READLN		| Reads a logical line of text from  the  current |
     |			| input stream into the line buffer.		  |
     ----------------------------------------------------------------------
						(continued on next page)



				      1-5
				 INTRODUCTION


			      Table 1-1  (Cont.)
	     Summary of Commonly Used Resident (Field 0) Routines

     ----------------------------------------------------------------------
     | Name		|		Function			  |
     |------------------|-------------------------------------------------|
     | ROTL6		| Rotates the accumulator (AC)  and  the  link  6 |
     |			| bits leftward.				  |
     |			|						  |
     | SCAN		| Skips over a sequence of spaces and tabs.	  |
     ----------------------------------------------------------------------



     1.3.5  Local (Page) Symbols

     In some modules, you will find that unimportant  symbols  are  created
     by  appending  a  single  letter  (or  digit) to the end of the module
     name.  Such symbols are referenced  only  within  the  (listing)  page
     where  they  reside;   they  can  be  converted  to  local  symbols if
     necessary.



     1.4  ROUTINE CALLING CONVENTIONS



     1.4.1  ERROR Routine Calls

     Almost all calls to the ERROR routine have labels of the form:

	  ERnn or IOnn

     where:

	  nn is the error number

     These labels are defined as external symbols in the MACERR module.



     1.4.2  Subprogram Interfaces and Calling Sequences

     Most of MACREL's main routines  reside  in  Field  0,  while  the  I/O
     routines    reside   in   Field   1.    This   minimizes   cross-field
     communication.  When a cross-field call or jump is  necessary,  MACREL
     does  not  use  the  general  PDP-8  calling convention of setting the
     data field to the current field.   This  is  because  MACREL  routines
     know the fields where their callers are located.

     Also, for further efficiency, most Field 0  routines  are  written  so
     that  they  can only be called from Field 0.  For the rare cases where
     it is necessary to call these routines from  Field  1,  the  auxiliary

				      1-6
				 INTRODUCTION


     subroutine  CALLIT  is  used.  For example, if a routine in Field 1 is
     to call a routine SUB in Field 0, the call would be as follows:

	  CIF 0
	  JMS I (CALLIT
	  SUB

     This allows routines to  pass  an  argument  back  and  forth  in  the
     accumulator (AC).



     1.4.3  Overlay Module Calling Conventions

     When control passes to a routine  that  resides  in  an  overlay,  the
     routine  that  is  currently running must call the overlay loader LOAD
     by using the calling sequence described in Section 2.17.7.

     In many cases, the  calling  routine  will  then  pass  control  to  a
     routine  in  the  overlay  by a JMP or JMS to an entry point that is a
     global symbol.  Since the   symbol  will  be  in  the  cross-reference
     listing,  you  can easily locate its origin and other references.  For
     example, if in Overlay 6 there is an entry  point  named  CMPLXE,  the
     call to this code from MAC24 is:

	  JMS I (LOAD
	  AUXOVR+6
	  JMP I (CMPLXE

     The loader loads Overlay 6 into the area  that  begins  with  location
     AUXOVR, and the calling routine then passes control to CMPLXE.

     In other cases, the calling routine will simply pass  control  to  the
     first  location  in  the  overlay  area  rather  than to a named entry
     point of a routine in the overlay.  For  example,  if  in  Overlay  10
     (FIN0),  the  module's  code  begins  with  the tag NEXTT, the call to
     this code from MAC24 is:

	  JMS I (LOAD
	  INHAND+10
	  JMP I .+1
	  INHAND

     The loader loads Overlay 10 into  the  overlay  area  that  begins  at
     INHAND,  and  the  calling  routine  then branches to the beginning of
     the overlay area.  Thus, the call to the entry point  in  the  overlay
     is   difficult  to  locate  in  a  listing,  since  the  call  is  not
     associated with a symbol in the cross-reference listing.



     1.5  DATA FORMATS AND REPRESENTATIONS



				      1-7
				 INTRODUCTION


     This section describes  MACREL's  character  codes,  packing  schemes,
     and data formats, including the symbol table.



     1.5.1  Character Encoding and Packing Schemes

     MACREL  uses  three  different  character  codes  and  two   character
     packing  schemes  for  its  internal operations.  (This is in addition
     to the .ENABLE directive's character packing options described in  the
     MACREL/LINK   User's  Manual.)  The  character  codes  are:   MACREL's     ____________________________
     special 6-bit code and the ASCII 6-bit and 7-bit codes  (described  in
     Appendix X).  The packing schemes are:  OS/8 and 6-bit.

     MACREL accepts characters for input in 7-bit  ASCII  (the  eighth  bit
     is  ignored),  that  are packed using the OS/8 packing scheme shown in
     Figure 1-1.


		bit 0		    3 4			 11
	           -----------------------------------------
	   word 1  |   character 3   |     character 1     |
	           |   (bits 0 - 3)  |		           |
	           |-----------------|---------------------|
	   word 2  |   character 3   |     character 2     |
	           |   (bits 4 - 7)  |		           |
	           -----------------------------------------
						   ML-027-80

		   Figure 1-1  OS/8 ASCII Character Packing


     For storage in the symbol  table,  MACREL  converts  these  characters
     either  into  MACREL 6-bit code or into 6-bit ASCII code (depending on
     the operation).  It packs  the  characters  two  characters  per  word
     (6-bit  packing)  and  maps the lower-case ASCII characters into their
     upper-case equivalents.

     MACREL converts characters for output into  OS/8  packed  8-bit  ASCII
     (7-bit ASCII with parity bit always set).



     1.5.2  15-Bit Pointers

     The 15-bit pointer is a method for encoding  a  15-bit  address  in  a
     12-bit word.  Figure 1-2 illustrates the format.








				      1-8
				 INTRODUCTION


		bit 0	       2 3	      11
	           ------------------------------
		   |	field	|    address    |
	           ------------------------------
		       ^	    ^		       |	    |
		       |	    |
		       |	    --- 12-bit location divided by 8. Append
		       |		three zeros to the right of this
		       |		value to obtain the complete
		       |		address.
		       |
		       --- Memory field of location.		  ML-028-80

		       Figure 1-2  15-Bit Pointer Format



     1.5.3  Chunks

     MACREL formats all memory not used by itself or by  OS/8  into  8-word
     groups  called  chunks.   It  links these chunks together into a chain
     from which it  allocates  memory  for  both  symbol  table  and  macro
     storage.   The  first  word  of each chunk contains the 15-bit pointer
     to the next chunk.  Location FREESPACE  contains  the  15-bit  pointer
     to  the  first  chunk  in  the  chain.   The  last  chunk in the chain
     contains a pointer of zeros.



     1.5.4  Symbol Table Organization

     The symbol table is a  collection  of  linked  lists  called  buckets.
     There  are  100  (octal)  buckets  in  the  symbol  table.   They  are
     assigned numbers in the range 0 through 77.  Each bucket  consists  of
     0  or  more  chunks  linked together with 15-bit pointers.  Each chunk
     in a bucket contains the data  for  one  symbol  (that  is,  a  symbol
     table  entry).   Each  entry  is  sorted into one of the buckets.  The
     sort is based on a match between the  bucket  number  and  the  number
     formed  by  the  first  6  bits of the first character of the symbol's
     name (or bits 0 through 5 of word 1 of the symbol table entry).



     1.5.4.1  Character  Codes  for  Symbol  Table  Entries  -  Except  for
     symbol  table  entries  with  extended  names, MACREL uses the special
     character codes shown in Table A-1 (Appendix A)  when  storing  symbol
     names in the symbol table.



     1.5.5  Symbol Table Entry Formats

     MACREL stores a symbol's information in  the  symbol  table  using  an
     entry  format  that  is based on the symbol type.  The flag word (word

				      1-9
				 INTRODUCTION


     5) of each entry specifies the symbol's type as shown  in  Table  1-2.
     The sections that follow describe these formats.


				   Table 1-2
			    Symbol Table Flag Word

     ----------------------------------------------------------------------
     |  Bit	     |	      Meaning					  |
     |		     |	 (when set to 1)				  |
     |---------------|----------------------------------------------------|
     |		     |							  |
     |	0	     |	Symbol is defined				  |
     |	1	     |	Symbol is a memory reference instruction (MRI)	  |
     |	2	     |	Symbol is a permanent symbol			  |
     |	3	     |	Symbol was defined during pass 1		  |
     |	4	     |	Symbol is a local symbol			  |
     |	5	     |	Symbol was defined before being referenced or	  |
     |		     |	is an unnamed program section			  |
     |		     |							  |
     |	6-8	     |	 0 = Not a program section			  |
     |		     |	 1 = .ASECT					  |
     |		     |	 2 = .RSECT					  |
     |		     |	 3 = .FSECT					  |
     |		     |	 4 = .DSECT					  |
     |		     |	 5 = .ZSECT					  |
     |		     |	 6 = .XSECT					  |
     |		     |	 7 = Reserved					  |
     |		     |							  |
     |	9-11	     |	 0 = Regular symbol				  |
     |		     |	 1 = User macro					  |
     |		     |   2 = Pseudo-macro (PSEUM)			  |
     |		     |	 3 = Pseudo-operator (PSEUD) directive		  |
     |		     | * 4 = .ENTRY					  |
     |		     | * 5 = .GLOBAL symbol				  |
     |		     | * 6 = .EXTERNAL					  |
     |		     | * 7 = .ZTERNAL					  |
     ----------------------------------------------------------------------
	* Bit 9 is set to 1 when the symbol belongs to the LSD.
	  If the symbol is undefined, all other bits are ignored.



     1.5.5.1  Regular Symbol Table Entry  Format  -  Table  1-3  shows  the
     format of a symbol table entry for a regular symbol.  If the symbol is
     a numeric local symbol or a literal, it is entered in the symbol table
     as  a regular symbol with an extended name in words 1 through 3 of the
     entry, as shown in Tables 1-4 and 1-5.







				     1-10
				 INTRODUCTION


				   Table 1-3
		    Format for Regular Symbol Table Entries

     ----------------------------------------------------------------------
     |	  Word	  |			Use				  |
     |------------|-------------------------------------------------------|
     |	   0	  | 15-bit pointer to next chunk in the bucket		  |
     |	   1	  | char 0 /char 1					  |
     |	   2	  | char 2 /char 3					  |
     |	   3	  | char 4 /char 5					  |
     |	   4	  | absolute value					  |
     |	   5	  | flag (see Table 1-2)				  |
     |	   6	  | 15-bit .SECT pointer				  |
     |     7	  | LSD number						  |
     ----------------------------------------------------------------------
	Note:   char = character of symbol name in MACREL 6-bit code.


				   Table 1-4
	  Format for Regular Symbol Table Entries with Extended Names

     ----------------------------------------------------------------------
     |  Word |			    Use					  |
     |-------|------------------------------------------------------------|
     |	     |								  |
     |	 0   | 15-bit pointer to next chunk in the bucket		  |
     |	 1   | bits							  |
     |	     |    0-5 = typcode	      = 36 or 76 to signify extended name |
     |	     |    6-11 = prechar      = 6-bit ASCII (space, V or L)	  |
     |	 2   | number		      = symbol name, literal value, or	  |
     |	     |				literal address			  |
     |	 3   | bits							  |
     |	     |    0 = r		      = 0 (octal radix) or 1 (decimal	  |
     |	     |				radix)				  |
     |	     |    1-5 = unused						  |
     |	     |    6-11 = postchar     = 6-bit ASCII ( $ or + )		  |
     |	 4   | absolute value						  |
     |	 5   | flag (see Table 1-2)					  |
     |	 6   | 15-bit .SECT pointer					  |
     |	 7   | LSD number						  |
     ----------------------------------------------------------------------














				     1-11
				 INTRODUCTION


				   Table 1-5
		    Extended Symbol Name Field Definitions

     ----------------------------------------------------------------------
     |	     Use	 | prechar | number  |     r	 |    postchar	  |
     |			 | (6-bit) |	     |  (radix)  |    (6-bit)	  |
     |-------------------|---------|---------|-----------|----------------|
     | Numeric Local	 | <space> | symbol  | name	 | 1 (decimal) $  |
     | Symbol		 |	   |	     |		 |		  |
     |			 |	   |	     |		 |		  |
     | Literal Reference |	   | literal |		 |		  |
     | by Value		 |    V	   | value   | 0 (octal) | + (if	  |
     |			 |	   |	     |		 |   relocatable) |
     | Literal Reference |	   | literal |		 |		  |
     | by Location	 |    L	   | address | 0	 | + (if	  |
     |			 |	   |	     |		 |   relocatable) |
     ----------------------------------------------------------------------



     1.5.5.2  .MACRO Symbol Table Entry Format - Table 1-6 shows the format
     of a symbol table entry for a .MACRO name.


				   Table 1-6
		    Format for .MACRO Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | 15-bit pointer to the first chunk of the macro definition |
     |	 5    | flag (see Table 1-2)					  |
     |	 6    | 15-bit pointer to the last chunk of the macro definition  |
     |	 7    | unused							  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.3   Pseudo-Operator  and   Pseudo-Macro   Symbol   Table   Entry
     Format - Table 1-7 shows the format of a symbol table entry for either
     pseudo-operators or pseudo-macros.








				     1-12
				 INTRODUCTION


				   Table 1-7
	     Format for Pseudo-Operators (PSEUD) and Pseudo-Macros
			 (PSEUM) Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    |	15-bit pointer to next chunk in the bucket		  |
     |	 1    |	char 0 /char 1						  |
     |	 2    |	char 2 /char 3						  |
     |	 3    |	char 4 /char 5						  |
     |	 4    |	12-bit address to Field 0 routine (flag = PSEUD) or entry |
     |	      |	into overlay (PSEUM) if flag = PSEUM.			  |
     |   5    |	flag (see Table 1-2)					  |
     |	 6    |	number of overlay to load if PSEUD, or unused if PSEUM	  |
     |	 7    |	unused							  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.4  .EXTERNAL Symbol Table Entry  Format - Table  1-8  shows  the
     format of a symbol table entry for a .EXTERNAL symbol.


				   Table 1-8
		   Format for .EXTERNAL Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | unused							  |
     |	 5    | flag (see Table 1-2)					  |
     |	 6    | unused							  |
     |   7    | LSD number						  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.5  .ASECT Symbol Table Entry Format - Table 1-9 shows the format
     of a symbol table entry for an .ASECT symbol.







				     1-13
				 INTRODUCTION


				  Table 1-9
		    Format for .ASECT Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | highest current location counter (PC) value in the .ASECT |
     |	 5    | flag (see Table 1-2)					  |
     |	 6    | 15-bit pointer to auxiliary symbol table chunk (See	  |
     |	      | Table 1-13)						  |
     |	 7    | LSD number						  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.6  .DSECT Symbol Table Entry  Format  -  Table  1-10  shows  the
     format of a symbol table entry for a .DSECT symbol.


				  Table 1-10
		    Format for .DSECT Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | lowest current location counter (PC) value in the .DSECT  |
     |	      | (length of the program section)				  |
     |	 5    | flag (See Table 1-2)					  |
     |	 6    | 15-bit pointer to auxiliary symbol table chunk (see	  |
     |	      | Table 1-13)						  |
     |	 7    | LSD number						  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.7  .RSECT Symbol Table Entry  Format  -  Table  1-11  shows  the
     format of a symbol table entry for an .RSECT symbol.






				     1-14
				 INTRODUCTION


				  Table 1-11
		    Format for .RSECT Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | highest relative current location counter (PC) value in	  |
     |	      | the .RESCT (length of the program section)		  |
     |	 5    | flag (see Table 1-2)					  |
     |	 6    | 15-bit pointer to auxiliary symbol table chunk (see	  |
     |	      | Table 1-15)						  |
     |	 7    | LSD number						  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.8  .FSECT .XSECT and .ZSECT Symbol  Table  Entry  Format - Table
     1-12  shows  the  format  of  a  symbol table entry for .FSECT, .XSECT
     and .ZSECT symbols.


				  Table 1-12
		     Format for .XSECT, .ZSECT, and .FSECT
			     Symbol Table Entries

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	 1    | char 0 /char 1						  |
     |	 2    | char 2 /char 3						  |
     |	 3    | char 4 /char 5						  |
     |	 4    | highest location counter (PC) value in the program section|
     |	 5    | flag (see Table 1-2)					  |
     |	 6    | 15-bit pointer to auxiliary symbol table chunk (see Table |
     |	      | 1-13)							  |
     |	 7    | LSD number						  |
     ----------------------------------------------------------------------
	Note:  char = character of symbol name in MACREL 6-bit code.



     1.5.5.9  Auxiliary Symbol Table Chunk Entry Format - Table 1-13  shows
     the format of symbol table entry for an auxiliary chunk.  This type of
     entry is used only in conjunction  with  the  program  section  symbol
     table entries described in Sections 1.5.5.5 through 1.5.5.7.


				     1-15
				 INTRODUCTION


				  Table 1-13
		   Symbol Table Layout for Auxiliary Chunks
				 (.SECTs only)

     ----------------------------------------------------------------------
     |	Word  |				Use				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     |	 0    | 15-bit pointer to next chunk in the bucket		  |
     |	      |								  |
     |	 1    | bits 0-2    = field number for absolute program sections  |
     |	      |								  |
     |	      |	    = restriction type for relocatable program	  |
     |	      |	      sections:					  |
     |	      |								  |
     |	      |		0 = No restriction			  |
     |	      |		1 = Absolute field restriction specified  |
     |	      |		    in word 2				  |
     |	      |		2 = 12-bit absolute PC restriction in	  |
     |	      |			    word 2				  |
     |	      |		3 = Same page and field as 15-bit pointer |
     |	      |		    in word 2				  |
     |	      |		4 = Same field as 15-bit pointer in word 2|
     |	      |		    bits 4-11 = LSD number		  |
     |	      |								  |
     |	 2    | restriction for the PC according to the contents of bits  |
     |	      | 0-2 in word 1 (above).  (For .ASECTs this word is low	  |
     |	      | current location counter (PC).)				  |
     |	      |								  |
     |	 3    | LEVEL/OVERLAY:  bits 0-2 = 0				  |
     |	      |		5-7 = level number			  |
     |	      |		8-11 = overlay number			  |
     |	      |								  |
     |	 4    | bits 0-10 = unused					  |
     |	      |        11 = CONCAT keyword				  |
     |	      |	    0 = not specified				  |
     |	      |	    1 = specified				  |
     |	      |								  |
     |	 5    | Length of .FSECT without literals			  |
     |	      |								  |
     |	 6    | unused							  |
     |	      |								  |
     |	 7    | unused							  |
     ----------------------------------------------------------------------



     1.6  TABLES, STACKS, AND BUFFERS

     Table 1-14 lists the tables, stacks, and buffers contained in  MACREL.
     They  are  discussed  either in the detailed description of the module
     where they reside or in the comments of the assembly listing for  that
     module.


				     1-16
				 INTRODUCTION


				  Table 1-14
		    Summary of Tables, Stacks, and Buffers

     ----------------------------------------------------------------------
     |   Name	|  Module  |  Section |		 Description		  |
     |----------|----------|----------|-----------------------------------|
     |		|	   |	      |					  |
     |	AT	|  MACRO   |  2.13    | Actual .MACRO Argument Table	  |
     |		|	   |	      |					  |
     |	CURPAG	|  MACIO   |  2.9.8   |	Current Page Literal Table	  |
     |		|	   |	      |					  |
     |	EXPSTK	|  MACIO   |   ---    | Expression Parser Stack		  |
     |		|	   |	      |					  |
     |	FT	|  MACMAC  |  2.10.1  |	Formal (dummy) .MACRO Argument	  |
     |		|	   |	      |	Table				  |
     |		|	   |	      |					  |
     |	INPBUF	|  MACIO   |  2.8.2   |	Input Buffer			  |
     |		|	   |	      |					  |
     |	LIMTBL	|  MACINI  |  2.7.4   |	Memory Limit Table		  |
     |		|	   |	      |					  |
     |	LINBUF	|  MACIO   |  2.17.16 | Line Buffer			  |
     |		|	   |	      |					  |
     |	MACTBL	|  MACTBL  |  2.15    |	Character Branch Table		  |
     |		|	   |	      |					  |
     |	MESLIST	|  MACERR  |  2.5     |	Error Message Pointer Table	  |
     |		|	   |	      |					  |
     |	MESTBL	|  MACERR  |  2.5     |	Error Message Table		  |
     |		|	   |	      |					  |
     |	PAGE0	|  MACIO   |  2.9.8   |	Page 0 Literal Table		  |
     |		|	   |	      |					  |
     |	PTRTBL	|  FIN3	   |  2.4.1   |	Symbol Table Listing Format	  |
     |		|	   |	      | Pointer Table			  |
     |		|	   |	      |					  |
     |	OUTBUF	|  MACIO   |  2.8.14  |	Output Buffer			  |
     |		|	   |	      |					  |
     |	RADBUF	|  EXPOVR  |  2.1.1   |	Contains value of current term	  |
     |		|	   |	      |	in the current radix		  |
     |		|	   |	      |					  |
     |	STRSTK	|  MACIO   |  2.2.10  |	Input Coroutine Stream Stack	  |
     |		|	   |	      |					  |
     |	SYMTAB	|  MACINI  |  2.7.6   |	Initial Permanent Symbol Table	  |
     |		|	   |	      |					  |
     |	USRSTK	|  MACIO   |  2.29.5  |	PUSH and .POP Directives'	  |
     |		|	   |	      | Stack				  |
     ----------------------------------------------------------------------



     1.7  DEFAULT CONDITIONS

     All default operating conditions  are  explained  in  the  MACREL/LINK								___________
     User's  Manual.  The default value for an undefined symbol is absolute     ______________
     0.


				     1-17
				 INTRODUCTION


     1.8  ERROR AND EXCEPTION REPORTING

     Whenever  possible,  MACREL  attempts  to  continue  after  an  error.
     Therefore,  it  processes  error  calls using a JMS instruction rather
     than a JMP instruction when calling the error message processor ERROR.
     When  control  returns to the calling routine, it attempts to continue
     processing the current line.  If this is not possible,  it  scans  the
     remainder  of the line looking for an end-of-statement delimiter so it
     can parse the next line.

     MACREL's main operating concept is that assembly  should  continue  at
     all  costs.   For example, when the symbol table becomes full, further
     assembly is not possible.  Rather than terminating  operation,  MACREL
     displays   an   error   message  and  simulates  an  end-of-input-file
     condition.  This allows it to proceed to the next  pass  so  that  the
     user  can  obtain  a  partial  listing  of  the program, no matter how
     catastrophic the error.

     MACREL also displays error  messages  at  the  terminal  that  are  of
     sufficient  detail to let the user correct the error without resort to
     a listing.


































				     1-18






				   CHAPTER 2

			  DESCRIPTIONS OF THE MODULES



     This chapter contains the detailed  descriptions  of  the  modules  in
     MACREL.   They  are  presented  in  alphabetical order by module name.
     Table 2-1 lists the modules and the sections where they are described.
     Within  each module description, the various routines are described in
     order of their appearance in the source code.


				   Table 2-1
			     MACREL Module Summary

     ----------------------------------------------------------------------
     | Module |			      Description		| Section |
     |--------|-------------------------------------------------|---------|
     | EXPOVR |	Overlay to the expression processor module	| 2.1	  |
     |	      |	(MACEXP)					|	  |
     |	      |							|	  |
     | FIN0   |	Pass initialization overlay			| 2.2	  |
     |	      |							|	  |
     | FIN2   | End-of-pass overlay for passes 1, 2, and 4	| 2.3	  |
     |	      |							|	  |
     | FIN3   | End-of-pass overlay for pass 3			| 2.4	  |
     |	      |							|	  |
     | MACERR | Error message overlay				| 2.5	  |
     |	      |							|	  |
     | MACEXP | Expression processor (resident)			| 2.6	  |
     |	      |							|	  |
     | MACINI | Once-only initialization code			| 2.7	  |
     |	      |							|	  |
     | MACIO  | I/O module (resident)				| 2.8	  |
     |	      |							|	  |
     | MACLIT | Literal processor overlay			| 2.9	  |
     |	      |							|	  |
     | MACMAC |	Macro processor (overlay)			| 2.10	  |
     |	      |							|	  |
     | MACOPN |	File open routines (overlay)			| 2.11	  |
     |	      |							|	  |
     | MACORG |	Program counter (origin) processor (overlay)	| 2.12	  |
     |	      |							|	  |
     | MACRO  |	Macro processor (resident)			| 2.13	  |
     |	      |							|	  |
     | MACRTH |	Global arithmetic processor (overlay)		| 2.14	  |
     |	      |							|	  |
     | MACTBL |	Character branch table (resident)		| 2.15	  |
     ----------------------------------------------------------------------
						 (continued on next page)

				      2-1
			  DESCRIPTIONS OF THE MODULES


			       Table 2-1 (Cont.)
			     MACREL Module Summary

     ----------------------------------------------------------------------
     | Module |			      Description		| Section |
     |--------|-------------------------------------------------|---------|
     | MAC2   |	Code specific to passes 2 and 4 (resident)	| 2.16	  |
     |	      |							|	  |
     | MAC24  |	Main routines (resident)			| 2.17	  |
     |	      |							|	  |
     | MAC30  |	Code specific to passes 1 and 3 (overlay)	| 2.18	  |
     |	      |							|	  |
     | MAC3R  |	Code specific to passes 1 and 3 (resident)	| 2.19	  |
     |	      |							|	  |
     | OVRA   |	.PAGE, ZBLOCK, and .TEXT directives (overlay)	| 2.20	  |
     |	      |							|	  |
     | OVRB   | Conditional assembly directives (overlay)	| 2.21	  |
     |	      |							|	  |
     | OVRC   |	Radix control, FILENAME, DEVICE,		| 2.22	  |
     |	      |	.ENABLE, and .DISABL directives (overlay)	|	  |
     |	      |							|	  |
     | OVRD   |	Program section (.SECT) directives (overlay)	| 2.23	  |
     |	      |							|	  |
     | OVRE   |	Global declarations and .INCLUDE and .CHAIN	| 2.24	  |
     |	      | directives (overlay)				|	  |
     |	      |							|	  |
     | OVRQ   |	Block letter printer (overlay)			| 2.25	  |
     |	      |							|	  |
     | OVRR   |	Listing directives, pre-end-of-pass		| 2.26	  |
     |	      |	overlay, and .START, .JSW, .VERS, NOPUNCH, and  |	  |
     |	      |	ENPUNCH directives (overlay)			|	  |
     |	      |							|	  |
     | OVRS   |	FIXTAB and EXPUNGE directives (overlay)		| 2.27	  |
     |	      |							|	  |
     | OVRT   | FIELD directive and "pass 5 " (post-processing) | 2.28	  |
     |	      |	(overlay)					|	  |
     |	      |							|	  |
     | OVRU   |	.TITLE, .SBTTL, RELOC, .PUSH, and .POP		| 2.29	  |
     |	      | directives (overlay)				|	  |
     |	      |							|	  |
     | PAS2   |	Code specific to passes 2 and 4 (overlay)	| 2.30	  |
     ----------------------------------------------------------------------



     2.1  EXPOVR (Overlay 32)

     This module is an  auxiliary  overlay  for  the  expression  processor
     module (MACEXP).



     2.1.1  BACKL


				      2-2
			  DESCRIPTIONS OF THE MODULES


     The routine BACKL processes the backslash (\) operator.   Its  calling
     sequence is:

	  JMS BACKL
	  routine

     where:

	  routine is the address of the routine that receives characters

     BACKL performs the following operations:

	  1.  Stores the state of the symbol parser (PARSYM  in  MAC24)  on
	      the  expression  stack  (EXPRSTK)  by  saving the contents of
	      locations:  FILESW,  PDSWT,  IDKNT,  DOLFLG,  NAMPTR,  NAME1,
	      NAME2,  NAME3,  NAME4, PARSYM, UNARYM, and TERM.  This is for
	      cases where BACKL is called during a symbol parse  operation.
	      This  serves no purpose when BACKL is called while processing
	      an actual macro argument (MC in OVRX).


					  NOTE

			BACKL must save TERM  because  it  calls
			the term processor recursively to obtain
			the value of the term that  follows  the
			backslash.


	  2.  Parses a term by calling TERM.  An error results if the value
	      of the term is not absolute.

	  3.  Removes the values saved previously from EXPRSTK  to  restore
	      the context of the current invocation of TERM.

	  4.  Converts the value of the term to its representation  in  the
	      current  radix.   The  number  is  treated  as unsigned.  The
	      conversion is accomplished by dividing the term  successively
	      by  RADXWD  and  storing  the  result temporarily in a 6-word
	      buffer called RADBUF.  The  computed  digits  are  stored  in
	      reverse  order.   RADBUF  is terminated by a negative number.
	      Five divisions are  always  performed,  because  dividing  to
	      completion  could cause buffer overflow if the radix is small
	      (for example, a two).  Therefore, the  routine  returns  only
	      the low order five digits of the result.

	  5.  Scans the buffer in  a  forward  direction  ignoring  leading
	      zeros and sending the remaining characters to the appropriate
	      routine, by using the call:

		   TAD char
		   JMS I SNDRTN

	      where:

				      2-3
			  DESCRIPTIONS OF THE MODULES



		   char	      is a MACREL 6-bit code for any numeric
			      character (0 through 9)

		   SNDRTN     points to one of two routines specified by
			      the caller

	  6.  Causes SNDRTN to point to SYMSTO (MAC24)  if  called  by  the
	      symbol  parser, PARSYM (MAC24).  SYMSTO packs characters into
	      MACREL 6-bit code and places them in locations NAME1  through
	      NAME4 of the symbol table work area (MAC24).

	  7.  Causes SNDRTN to point to STORMS (MACRO)  if  called  by  the
	      actual  macro argument processor, MC (MACMAC).  STORMS stores
	      characters in macro argument space.

     The following is a list of common variables that BACKL uses:

	  LD0FLG      Leading  zero  flag.   It  is  set  to  zero  at  the
		      beginning  of  the second scan through RADBUF.  It is
		      set to a non-zero value if a non-zero digit is found.
		      Thus, a zero means a leading zero.

	  RADPTR      Points to RADBUF.

	  SNDRTN      Contains the  address  of  the  routine  that  is  to
		      receive  the  digits  (in  radix representation) that
		      followed the backslash.

	  BCKNT	      Counter that prevents  overflow  of  RADBUF.   It  is
		      initially set to -5.



     2.1.2  IDIV

     IDIV is a routine that performs 12-bit unsigned division by repeatedly
     subtracting  the  divisor  from the dividend.  The quotient is left in
     the AC and the remainder is deposited in REMAIN.  If the divisor is 0,
     an  error  message is generated and the quotient is set to 0, with the
     number becoming the  remainder.   It  tests  the  link  to  check  for
     completion.   QUO  contains  the partial quotient while the routine is
     running.

     The calling sequence is:

	  TAD dividend
	  JMS IDIV
	  12-bit address of divisor



     2.1.3  IMUL


				      2-4
			  DESCRIPTIONS OF THE MODULES


     The  routine  IMUL  performs   12-bit   unsigned   multiplication   by
     successively adding the multiplicand to itself.  The multiplier is the
     iteration count.  The temporary product resides in QUO, and the  final
     product in the AC.

     The calling sequence is:

	  TAD multiplicand
	  JMS IMUL
	  12-bit address of multiplier



     2.1.4  SNGLQQ

     The routine SNGLQQ processes the single  quote  (')  ASCII  conversion
     operator.   It  is  called by the expression processor (MAXEXP) when a
     single quotation mark occurs at  the  beginning  of  a  term.   SNGLQQ
     performs the following operations:

	  1.  Calls (QQ)GETKAR (MAC24) to get the next two characters  from
	      the input stream.

	  2.  Converts the two characters into 6-bit ASCII and  packs  them
	      into  one  word.   The  first  character  resides in the most
	      significant six bits, and the second character in  the  least
	      significant six bits.

	  3.  Stores the result as an absolute value in TRMABS.

	  4.  Generates an error message and aborts the  statement  if  two
	      characters do not follow the single quote.

	  5.  Calls (QQ)GETCHR (in MAC24) so that the first character after
	      this term becomes the current character.


					  NOTE

			SNGLQQ does not zero the  relative  part
			of  the  term.  Instead, MACEXP performs
			this task when SNGLQQ returns control to
			it.

	  6.  Returns to the calling routine with the two 6-bit  characters
	      packed in the AC.



     2.1.5  UPAROQ

     The routine UPAROQ implements  the  temporary  (local)  radix  control
     command  constructs:  B, D, and O, and the control character construct


				      2-5
			  DESCRIPTIONS OF THE MODULES


     ".  It is called  from  the  expression  processor  (MACEXP)  when  it
     encounters an uparrow (^) at the beginning of a term.

     UPAROQ performs the following operations:

	  1.  Saves the current  radix,  residing  in  RADXWD  (MAC24),  by
	      storing it in HLDRAD.

	  2.  Reads the next character, and takes action according to which
	      one of the following situations obtains:

	      a.  If the routine finds no character, it assumes the end  of
		  line  was reached, generates an error message, and aborts
		  the statement.

	      b.  If it finds a character other than B,  D,  O,  or  ",  it
		  generates  an error, sets the result (TRMABS, TRMREL, and
		  TRMCOD) to absolute 0, and returns to the caller.

	      c.  If the routine finds B, D, O, or ", it  branches  to  the
		  appropriate entry point.

		       Character    Entry Point      Condition

			   B	       BINOVR	     Binary radix
			   D	       DECOVR	     Decimal radix
			   O	       OCTOVR	     Octal radix
			   "	       CNTCON	     Control Character


					  NOTE

			Decimal radix,  indicated  by  a  number
			that ends with a period (decimal point),
			is detected by  GETNUM  (MACEXP),  which
			sets DFLG to 0.

	  3.  Sets RADXWD to 10, 8, or 2 respectively, and  passes  control
	      to  the  radix  override  portion  of  the  code.   This code
	      determines whether the next character  is  a  digit.   If  no
	      digit  follows,  it generates an error message and aborts the
	      statement.  If a digit is present, it calls  GETNUM  (MACEXP)
	      to  parse  the  number  in the new (local) radix.  This value
	      becomes the absolute part of the resulting term.

	  4.  Restores the original radix, and checks to determine  if  the
	      current radix conflicts with the original radix.  If there is
	      a conflict (the number ended in a period [decimal point]  and
	      the  radix  override  option is not D), it generates an error
	      message.  (GETNUM indicates that  the  number  ended  with  a
	      period  by  setting DFLG to 0.) No error is generated if an D
	      preceded the number.  (This is redundant, but  not  an  error
	      condition.)


				      2-6
			  DESCRIPTIONS OF THE MODULES


				     NOTE

		   TENFLG always contains a 0, except  when
		   a  D is detected-in which case it is set
		   to 4000.  This indicates whether or  not
		   decimal radix is in effect so that radix
		   conflicts can be detected.

		   UPAROQ does not zero the  relative  part
		   of  the  term.  Instead, MACEXP performs
		   this task when UPAROQ returns control to
		   it.

		   The CNTCON routine does  not  reside  in
		   this  module because it shares code with
		   the DBLQ routine in MACEXP.



     2.2  FIN0 (Overlay 10)

     FIN0 is the pass initialization overlay.  At  the  beginning  of  each
     assembly  pass, control returns to this module through its entry point
     NEXTT.


				     NOTE

		   The call to this module may be  hard  to
		   locate  in  the  listing and will not be
		   found in  the  cross-reference  listing.
		   This  is because the call does not refer
		   to the entry point NEXTT by  name.   The
		   call  occurs  at symbol INHAND (location
		   NEX+3) in MAC24.



     2.2.1  NEXTT

     The routine NEXTT is the entry point to this module.  It is called  at
     the beginning of each pass to perform the following tasks:

	  1.  Calls IONIT2 (MACIO in Field 1) to perform  preliminary  pass
	      initialization.

	  2.  Zeros location  01400  to  indicate  that  the  Pass-Specific
	      Overlay Area is unoccupied.

	  3.  Loads the  pass-specific  overlay,  using  either  MAC30  for
	      passes 1 and 3, or PAS2 for Passes 2 and 4.

	  4.  Increments the pass number (PASS in MAC24), and  branches  to
	      OPEN1,  OPEN2,  OPEN3, OPEN4, or FIN5 depending on which pass

				      2-7
			  DESCRIPTIONS OF THE MODULES


	      is beginning.  Each of these routines branches to  REIT  when
	      completion.   (If  a  routine  decides  to  abort  a pass, it
	      branches to  NEXTT  to  proceed  with  the  next  pass.   The
	      overlays are loaded redundantly when this happens.)



     2.2.2  OPEN1

     The routine OPENl opens the  table  of  contents  (TOC)  file  at  the
     beginning  of  Pass  1  by  calling  OPENTC (MACOPEN, Overlay 33).  On
     completion, control returns to REIT.



     2.2.3  OPEN2

     OPEN2 is a routine that calls OPEN (MACOPEN, Overlay 33) to  open  the
     binary  output file at the beginning of pass 2.  The default file name
     extension is .RB.  OPEN2 then stores the starting block number of  the
     file that resides in OUTLOC (MACIO) by depositing it in RBFILE (MACIO)
     in case the user requested chaining to  LINK.   This  is  because  the
     Command  Decoder's  output  file  table  contains  file  names  but no
     starting addresses.  Upon completion, control returns to REIT.  If the
     user  did  not  specify  a binary file, OPEN2 skip pass 2 by branching
     back to NEXTT.



     2.2.4  OPEN3

     OPEN3 is a routine that is called at the beginning of pass 3  to  open
     the  listing  file,  print  the  block  letter  heading, and print the
     table-of-contents.  It performs the following operations:

	  1.  Loads zeros into location LOCOFF (MACIO).  LOCOFF is used  by
	      the  OPEN (MACOPN) routine.  Whenever OPEN is called, it adds
	      the contents of LOCOFF to the starting block  number  of  the
	      file to establish the block where output is to begin.  During
	      pass 2 LOCOFF contains a value that is equal to the number of
	      blocks  in  the  Loader  Symbol  Dictionary (LSD) area of the
	      binary file.  This offset allows OPEN to skip over the file's
	      LSD area.  This result is not desirable during pass 3.

	  2.  Calls OPEN (MACOPEN) to open the listing file.   The  default
	      file  name  extension  is  .LS.   It  sends characters to the
	      output file in 8-bit character mode.

	  3.  (if no listing file was specified) Skips Pass 3 by  branching
	      back to NEXTT.

	  4.  (if a listing file was specified) Checks to see if  the  user
	      specified  the  /B  option.  If /B was not specified, control
	      branches to CPYTOC to print the  table-of-contents  (TOC)  in

				      2-8
			  DESCRIPTIONS OF THE MODULES


	      the  listing  file.   If  the  /B option was specified, OPEN3
	      proceeds to print a block letter heading at the  top  of  the
	      listing before branching to CPYTOC.

	      Each block letter  consists  of  a  number  of  basic  letter
	      blocks.  The basic letter block is the fundamental structural
	      element for creating block letters.  It consists of an  array
	      of  identical letters.  The width of the array varies between
	      1 and 3 letters, depending on the width  of  the  page.   The
	      horizontal  image  area  for a block letter is 6 basic letter
	      blocks wide (5 plus a space).  By changing the width  of  the
	      basic  letter  block,  the  overall width of the block letter
	      heading can be altered.  Since a file name can contain up  to
	      6 letters, a minimum of 36 character positions is required on
	      the output device to contain a block letter heading.

	  5.  Adjusts the block letter width relative to the width  of  the
	      listing  device  page  by  dividing  the  column width of the
	      listing device (WIDTH in MAC24) by 44(octal).  The  resulting
	      value  determines  the width of a basic letter block as shown
	      in Table 2-2.  If the result of the division is 0, the output
	      device's  width  is too small to print a block letter heading
	      and  control  branches  directly  to  CPYTOC  to  print   the
	      table-of-contents.   If  the  result is greater than 3, OPEN3
	      ignores it and maintains a basic letter block width of 3  for
	      devices wider than 108 columns.


				   Table 2-2
			 Basic Letter Block Widths vs
			 Listing Device Column Width

     ----------------------------------------------------------------------
     |	Listing Device Width		  | Basic Block Width		  |
     |------------------------------------|-------------------------------|
     |		1-35			  |    0 letters		  |
     |		36-71			  |    1 letter			  |
     |		72-107			  |    2 letters		  |
     |	     greater than 107		  |    3 letters		  |
     ----------------------------------------------------------------------

	  6.  Loads Overlay 21, the  block  letter  printer  BLKLET  (OVRQ)
	      and  Overlay  24,  MACREL's  fish  caricature  printer  BINFO
	      (OVRQ).

	  7.  Calls BLKLET to print the  block  letters.   (It  passes  the
	      width  of  the  basic letter block as a negative value in the
	      AC.)

	  8.  Calls BINFO to print the fish  caricature,  MACREL's  version
	      number, and the number of errors (if any).

	  9.  Calls CPYTOC to  send  the  table-of-contents  (TOC)  to  the
	      listing file.  Thereafter, control returns to REIT.

				      2-9
			  DESCRIPTIONS OF THE MODULES


     2.2.5  OPEN4

     OPEN4 is a routine that is called at the beginning of pass 4  to  open
     the   cross-reference   (KREF)   file.    It  performs  the  following
     operations:

	  1.  Loads zeros into location LOCOFF (MACIO).  LOCOFF is used  by
	      the  OPEN (MACOPN) routine.  Whenever OPEN is called, it adds
	      the contents of LOCOFF to the starting block  number  of  the
	      file to establish the block where output is to begin.  During
	      pass 2 LOCOFF contains a value that is equal to the number of
	      blocks  in  the  Loader  Symbol  Dictionary (LSD) area of the
	      binary file.  This offset allows OPEN to skip over the file's
	      LSD area.  This result is not desirable during Pass 4.

	  2.  It calls OPEN (MACOPN) to open the KREF output  file.   (OPEN
	      uses  the default extension .KF if one does not already exist
	      in the Command Decoder's output file table.) The output  mode
	      is 12-bit binary.

	  3.  Takes  action  according  to  which  one  of  the   following
	      circumstances obtains:

	      a.  If the user specified the /C option and did not  enter  a
		  device  or  file  name  as  the  third (KREF) output file
		  specification, OPEN4 inserts  the  default  specification
		  SYS:KF.TM  into  the  appropriate  position  in  the OS/8
		  Command Decoder's output file table.

	      b.  If the user did not specify the /C option or a KREF  file
		  specification,  OPEN4  skips  pass 4 by branching back to
		  NEXTT.

	      c.  If a KREF file was specified, OPEN4 stores  the  starting
		  block number of the KREF output file (OUTLOC in MACIO) in
		  location KFFILE (MACIO).  This information  in  necessary
		  if  the  user  requested  chaining  to  KREF,  since  the
		  starting block number is not stored in the file's Command
		  Decoder's file table.

	  4.  Upon completion, control returns to REIT.



     2.2.6  FIN5

     The routine FIN5 determines whether to  return  control  to  the  OS/8
     Monitor or to chain to KREF or LINK.  It is called after all requested
     passes are processed.  If the user selected the /L, /G, or /C options,
     FIN5  passes  control  to location LNKCHN in Overlay 24 (OVRT) to scan
     the options, modify the command decoder area, and set up the chain  to
     KREF  or  LINK  as specified.  If none of these options was specified,
     MACREL operation is complete and FIN5  returns  control  to  the  OS/8
     Monitor by branching to absolute location 7605.

				     2-10
			  DESCRIPTIONS OF THE MODULES


     2.2.7  AINIT

     The routine AINIT sets initial values before starting each  pass.   It
     performs the following operations:

	  1.  CONCNT to 0,  to  indicate  that  there  are  no  conditional
	      directives in effect.

	  2.  PAGENO (listing page number) to 0.

	  3.  LINENO and LINEN2 (listing line number) to 0.

	  4.  RELOK to 0, to inhibit RELOC directive.

	  5.  ERKNT (error counter) to 0.

	  6.  Increments PPASS (physical pass number) by 1 each time a pass
	      is actually begun.  Notice that PPASS is different from PASS,
	      which contains the logical pass number.   The  physical  pass
	      number  is  used  by  the  error processor (MACERR module) to
	      determine whether or not an error message should  be  printed
	      at the terminal.  (Many error messages only appear during the
	      first physical pass during which they occur).

	  7.  Deposits spaces in the subtitle line locations (SUBTL through
	      SUBTL+(SUBLEN-1)) in MAC24.

	  8.  Sets QUAL to 0, to indicate that a local symbol  block  (LSB)
	      is not being processed.

	  9.  Sets CURFLD (current field) to 0.

	 10.  Sets LITPAG (Page of the current page literals) to page 200.

	 11.  Sets PUNFLG to 0, to enable binary output (punching).

	 12.  Sets LITSCT to 0.

	 13.  Sets CLTLOC and ZLTLOC to 0 to indicate that no current  page
	      or Page 0 literals have been detected.

	 14.  Sets EXTPC to 0, to indicate that MACREL's current location
	      counter (PC) is not external (in case the last pass ended by
	      changing the current location counter to the value of an
	      external symbol).

	 15.  Calls UNNAM (MAC2) to set up the default program  section  to
	      be an unnamed absolute program section.

	 16.  Sets the initial values of ENABWD and LISTWD as the  contents
	      of   INIENAB   and   INILST  (the  initial  ENABLE  and  LIST
	      conditions) respectively.  You can patch these  locations  to
	      different  values  if  you want to establish your own initial
	      conditions.

				     2-11
			  DESCRIPTIONS OF THE MODULES


	 17.  Sets the default radix to be octal by depositing  10  (octal)
	      in RADXW.

	 18.  Deposits 0 in OLDSCT, to indicate that there was no  previous
	      .SECT  directive  in  effect.   (This  prevents  a  user from
	      starting with a .SECT directive.)

	 19.  Deposits 0 in ZSECTN to clear the name of any page 0  literal
	      program section.

	 20.  Deposits 0 in BNFLAG and PCFLAG so that no binary or  current
	      location  counter  (PC)  value will be printed in the listing
	      unless requested.

	 21.  Sets MACLEV (macro nesting level) to 0.

	 22.  Deposits 0 in LNKGEN, to indicate that a link  has  not  been
	      generated yet.

	 23.  Calls  IOINIT  (MACIO  in  Field  1)   to   perform   further
	      initialization.  (This code resides in MACIO [Section 2.8] to
	      reduce the number of globals in this module.)



     2.2.8  CPYTOC

     The routine CPYTOC copies the table-of-contents (TOC) from the scratch
     blocks  on  the system device (SYS:) to the listing file.  It performs
     the following operations:

	  1.  Checks to see if  a  table-of-contents  was  created  on  the
	      previous  pass.   By  examining  the  contents  of the .SBTTL
	      directive counter SBTKNT  (MAC24).   If  SBTKNT  contains  0,
	      there  are no .SBTTLs and CPYTOC exits.  Otherwise, it checks
	      to see if the output buffer is  empty.   (The  output  buffer
	      might  not  be  empty  if  the  block letter heading was just
	      printed and the last buffer has not been written yet.) If the
	      output  buffer  is  not empty, CPYTOC sends it to the listing
	      file by padding the buffer with  NULs  (repetitive  calls  to
	      (QQ)LISTER(MAC3R) with AC=0000).

	  2.  Begins the copy operation, starting at a  block  boundary  to
	      avoid a longer listing buffer.


				     NOTE

		   The extra  zeros  will  not  affect  the
		   block  length  of the file.  Any program
		   that  reads  this  file  should  discard
		   these NULs.



				     2-12
			  DESCRIPTIONS OF THE MODULES


	  3.  Copies the blocks directly from the scratch area on SYS:   to
	      the  listing  file.   It  reads  them  by making calls to the
	      system handler.   It  writes  them  out  by  calling  PUTBUF.
	      TOCSIZ specifies the number of blocks to transfer.


				     NOTE

		   If the system  handler  detects  a  read
		   error,  it is fatal.  This causes MACREL
		   to halt because there may be no  way  to
		   recover.



     2.2.9  REIT

     The routine REIT performs file initialization once an output  file  is
     opened.   It  calls AINIT to initialize variables, then passes control
     to LOOP (MAC24).



     2.2.10  IOINIT

     The routine IOINIT, though logically part of FIN0, resides in Field  1
     in module MACIO.  It performs the following pass initialization steps:

	  1.  Marks the stream input routines:  ORET, ZRET, MRET, and  RRET
	      as being unused.

	  2.  Initializes  AT1  (MAC24),  the  main  macro  argument  table
	      pointer.

	  3.  Sets OV1 to 0 to indicate that the number  of  nested  macros
	      does not exceed the nesting limit.

	  4.  Empties  the  stream  stack  by  zeroing  location   STRSTK+1
	      (MACIO).

	  5.  Calls SWITCH to establish ZGET as the  initial  stream  input
	      coroutine.   (This  coroutine  does nothing but return CTRL/Z
	      codes.)

	  6.  Calls SWITCH to establish  OGET  as  the  next  stream  input
	      coroutine.   This is a protective device to force a return to
	      ZGET  in  the  event  an  internal  error  in  the  coroutine
	      switching  mechanism  causes  stream stack underflow past the
	      initial OGET.

	  7.  Sets DVNO to 0 to signify to the OGET coroutine that no input
	      file  is open yet.  Thus, when the first character is sent to
	      OGET, READOS will be called, which in turn will branch to EOS
	      (MAC24) to read the first OS/8 input file.

				     2-13
			  DESCRIPTIONS OF THE MODULES


     2.2.11  IONIT2

     The routine IONIT2, although logically part of FIN0,  resides  in  the
     MACIO   module   in   Field   1.    It  performs  the  following  pass
     initialization steps:

	  1.  Zeros FILENO to indicate that the first input  file  has  not
	      been read.

	  2.  Sets INI.EN to 0 to indicate that no input file  blocks  have
	      been read.

	  3.  Deposits the pointer to the first input file specification of
	      the CD area in INPTR.



     2.3  FIN2 (Overlays 12 and 14)

     The FIN2 module consists of two overlays:  12 and  14.   They  perform
     general-purpose, end-of-pass tasks such as:  writing the Loader Symbol
     Dictionary (LSD) to the output file,  emptying  buffers,  and  closing
     files.   They are called at the end of passes 1, 2, and 4. Overlay 12,
     the main overlay, resides in the Extremities  Overlay  Area;   Overlay
     14,  the  auxiliary  overlay  resides  in  the Directives Overlay Area
     during pass 2.



     2.3.1  Unlabeled Routine

     This is an unlabeled routine that consists of  the  code  that  begins
     with  the  (overlay)  number 12 and ends at the label LSDOUT. There is
     no label because this routine is entered by a  direct  branch  to  the
     start of the overlay area.  It performs the following tasks:

	  1.  Zeros LSDNUM.  This step provides coding consistency. It  can
	      be  removed  without effect, since the contents of LSDNUM are
	      initially 0 when the overlay is loaded.

	  2.  (if this is the end of pass 2)

	      a.  Sends an end-of-text code (a word containing NUL with a 3
		  as the flag field value) to the binary file.

	      b.  Dumps the last buffer of binary code by calling ZPAD.

	      c.  Closes the binary file by calling CLOSO (MACIO).

	      d.  Calls FINIO (MACIO).

	      e.  Loads  the  extension  overlay  (Overlay  14)  and  calls
		  subroutine LSDINI.


				     2-14
			  DESCRIPTIONS OF THE MODULES


	  3.  Scans the symbol table according to the following conditions:

	      a.  If the symbol belongs to  the  Loader  Symbol  Dictionary
		  (LSD),  calls  LSDOUT.  A symbol belongs in the LSD if it
		  is a program section name (flag bits 6-8 are nonzero), or
		  if  it  is  EXTERNAL, ZTERNAL, ENTRY, or GLOBAL (flag bit
		  9=1).

	      b.  If the symbol is a  program  section  name,  the  routine
		  deposits zeros in SYMVAL (high current location counter).

	      c.  If the symbol is an .ASECT name, the routine sets word  2
		  of  the auxiliary chunk (low current location counter) to
		  -1 to indicate that the lowest location counter value  is
		  not yet determined.

	  4.  (if this is the end of pass 1) Estimates the number of blocks
	      required  to  store the LSD entries in the binary output file
	      and stores this value in LOCOFF (MACIO).  (The assumption  is
	      that all LSD entries are defined during pass 1.) It does this
	      by performing the following sequence:

	      a.  Computes the maximum  size  that  the  LSD  could  be  by
		  multiplying  the  number  of  LSD  entries  (LSDNUM) by 6
		  (since each LSD entry is not more than 6 words long).

	      b.  Adds this value to the maximum length of the LSD  preface
		  (currently assumed to be 40 [octal] words long).

	      c.  Rounds this result up to the  next  multiple  of  400  (a
		  block boundary) to produce the maximum expected length of
		  the LSD portion of the binary file.

	      d.  Stores this value in LOCOFF (MACIO).  The  OPEN  (MACOPN)
		  routine  uses  this  value  as an offset to determine the
		  first block of the binary file where it can begin storing
		  the LSD text.

	      The routine stores the text portion of the binary file before
	      the  LSD,  because  the  exact  lengths  of  floating program
	      sections that contain current page literals are unknown.


				     NOTE

		   Because  the  number  of  current   page
		   literals  may  decrease  due  to literal
		   sharing, the length of .FSECTs cannot be
		   determined until the end of pass 2.


	  5.  (if  this  is  the  end  of  pass   1   and   there   is   no
	      table-of-contents  [SBTKNT=0]) Branches  to  NEX  (MAC24)  to
	      proceed to the next pass.

				     2-15
			  DESCRIPTIONS OF THE MODULES


	  6.  Sends the last buffer to the output file and closes the file.
	      Two  different procedures are used depending upon whether the
	      output mode is binary or ASCII.

	      a.  If the output mode is ASCII, (that  is,  an  odd-numbered
		  pass), the routine:

			 i.    Transmits the last buffer to the output file
			       by  sending  a  bufferful  of CTRL/Zs to the
			       listing file ( (QQ)LISTER in  MAC3R).   This
			       guarantees  that  the  last  buffer  will be
			       written out and  that  the  output  file  is
			       terminated with a CTRL/Z.

			 ii.   Stores the length (in blocks) of the  output
			       file  contained  OUTSIZ  (MACIO)  in  TOCSIZ
			       (MAC24).  This information is used when  the
			       table  of  contents is copied to the listing
			       file at the start of pass 3.

			 iii.  Passes control to  NEX  (MAC24)  to  proceed
			       with the next pass.

	      b.  If the output mode is binary (that is,  an  even-numbered
		  pass),  and  if  this  is  also  the  end  of pass 2, the
		  routine:

		  Calls ZPAD to force the last buffer to be transmitted  to
		  the  output  file  and  to  pad the unused portion of the
		  Loader Symbol Dictionary (LSD) area in the file with NULs
		  (It could be that the length originally estimated for the
		  LSD  area  was  too  short.   For  example,  if  the file
		  contained  a  large  number  of  external  symbols.)  The
		  routine  writes  blocks  of NULs up to, but not including
		  the first text block.  The block  number  for  the  first
		  text  block  is stored in TXTBLK (MACIO).  If this is the
		  end of Pass 4, the routine calls Z PAD once to  dump  the
		  buffer.   Then  it  calls CLOSO (MACIO) to close the KREF
		  file.

	  7.  Control transfers to NEX (MAC24) to begin the next  pass  (if
	      there are any more).



     2.3.2  LSDOUT (Overlay 12)

     The subroutine LSDOUT sends the Loader Symbol Dictionary  (LSD)  entry
     information to the LSD portion of the binary output file.  It performs
     the following tasks:

	  1.  Increments the LSD number (LSDNUM) by 1, to maintain a  count
	      of  the  number  of  LSD entries.  LSDNUM also represents the
	      number of  the  current  LSD  entry.   The  LSD  entries  are

				     2-16
			  DESCRIPTIONS OF THE MODULES


	      numbered  and  are  sent  to  the binary file in alphabetical
	      order.  This is convenient for maintenance purposes, but  not
	      necessary for proper LINK operation.

	  2.  Inserts the LSD number for the current symbol  (LSDNUM)  into
	      bits  -11 of its QUAL word in the symbol table.  Any previous
	      contents of this field are lost.  LSDOUT stores the LSD entry
	      number,  because  the  LSD entry is referred to by its number
	      during output to the .RB file.

	  3.  Exits to FIN2 if this is not pass 2.

	  4.  Sends the 3 words containing the LSD entry's  name  by  using
	      PUTBIT (PAS2).

	  5.  Computes the type code used by  LINK  to  identify  this  LSD
	      entry   and  stores  it  temporarily  in  LTYPE.   Table  2-3
	      specifies these codes.


				   Table 2-3
			     LSD Entry Type Codes

			  --------------------------
			  |  Code     |	Entry Type |
			  |-----------|------------|
			  |	1     | .SECREF	   |
			  |	2     | .RSECT	   |
			  |	3     | .RSECT	   |
			  |	4     | .FSECT	   |
			  |	5     | .DSECT	   |
			  |    10     | .XSECT	   |
			  |    11     | .ZSECT	   |
			  |    14     | .GLOBAL	   |
			  |    15     | .ZTERNAL   |	
			  |    16     | .EXTERNAL  |
			  --------------------------


	  6.  Sends the type code to the LSD.  The code resides in the  low
	      order  4  bits  of  the  12-bit  word  (bits 8-11), while the
	      high-order 8 bits (bits 0-7) contain the LSD entry number  of
	      the  entry  that  this entry is relative to.  This address is
	      derived from the 15-bit pointer in the SYMSCT  (MAC24)  entry
	      for this LSD entry as follows:

	      a.  If this symbol is not a program section name  and  SYMSCT
		  is 0, it must be an EXTERNAL or ZTERNAL symbol.  The high
		  order 8 bits of the word are set to 0.

	      b.  If SYMSCT is a program section  name,  the  high-order  8
		  bits  must  contain  the restriction type as specified by
		  the high order 3 bits of the QUAL word (MAC24)  for  this


				     2-17
			  DESCRIPTIONS OF THE MODULES


		  LSD  entry.   (Refer to the MACREL/LINK User's Manual for					      _________________________
		  the definition of the LSD restriction types.)

	  7.  Sends the program section  length  to  the  LSD  (unless  the
	      symbol  is  XTERNAL  or  ZTERNAL).   Except  for .ASECTs, the
	      length is stored in the SYMVAL  (MAC24)  word  for  this  LSD
	      entry.   If  the  LSD  entry  is an .ASECT, the length of the
	      .ASECT is  obtained  by  subtracting  its  low  PC  (location
	      counter) value from its high PC value (SYMVAL).

	  8.  It returns control to the caller  if  the  symbol  is  not  a
	      program section name.  Otherwise, it continues with step 9.

	  9.  Sends the restriction word to the LSD.  The word is  the  LSD
	      number  of  the  symbol  table  entry specified by the 15-bit
	      pointer in word 2 of the auxiliary .SECT chunk  (see  Section
	      1.5.5.8)  for  the  current  LSD  entry.   If the entry is an
	      .ASECT, there is no restriction code and the field number  of
	      the .ASECT is sent instead.

	 10.  Sends the LEVEL/OVERLAY word (word 3 of the  auxiliary  .SECT
	      chunk) to the LSD if the program section is an overlay.



     2.3.3  ZPAD (Overlay 12)

     This subroutine inserts 400 (octal) NULs into the page buffer to force
     the current contents of the page buffer to be sent to the output file.



     2.3.4  LSDINI (Overlay 14)

     The routine LSDINI sends the Loader Symbol  Dictionary  (LSD)  Preface
     items  to  the  binary  output  file by performing successive calls to
     (QQ)PUTBIT (MAC2) via PUTHDR.  (See the MACREL/LINK User's Manual  and					     _________________________
     the program listing for more information on the LSD Preface.)

     The preface  items  reside  in  packets  within  LSDINI.   Their  form
     corresponds  approximately to that used for the external (binary file)
     preface.  Each packet begins with a negative number that specifies the
     number  of  words  in the packet (including the count word).  The next
     word in the packet is the item title  code  for  this  preface  entry.
     (See   MACREL/LINK  User's  Manual  for  the  code  definitions.)  The	    ___________________________
     remaining words in the packet contain the preface item data itself.

     LSDINI sends the first five packets as a group to the output file.  It
     sends  the  remaining  packets  individually  to the output file.  The
     number of packets being sent is passed to PUTHDR as a  negative  value
     in the AC.

     For  selected  packet   entries,   LDSINI   performs   the   following
     computations before sending them to the output file:

				     2-18
			  DESCRIPTIONS OF THE MODULES


	  1.  Obtains the current date from OS/8 and inserts  it  into  the
	      current  date packet.  This packet is 2 words long so that it
	      can contain dates after 1977.  LSDINI obtains the  additional
	      date bits location 07777 and inserts the entire word into the
	      packet.

	  2.  Inserts the page number into the  page  number  packet.   The
	      page  number  is  the contents of PAGENO (MAC24) plus 2.  The
	      increment of 2 is necessary to account for the fact that  the
	      symbol  table is  considered to be a page.  LINK does not use  
	      this information.

	  3.  Obtains the Job Status Word (JSW) from location JSW  (MAC24).
	      It sends the job status word packet to the binary file if the
	      .JSW directive is encountered;  JSWKEY (MAC24 is zero.)

	  4.  Sends the starting address packet to the output file  if  the
	      .START  directive  was  encountered;  STARTK (MAC24) is zero.
	      LSDINI computes one of the following item  title  codes  from
	      the contents of STARTR (MAC24):


		  Code		 Meaning

		    1    Starting address is absolute

		    2    Address is relocatable


	      If the contents of STARTR  are  less  than  10  (octal),  the
	      starting  address  is  absolute  and this number is the field
	      number.  Otherwise, the starting address is  relocatable  and
	      this  number is a 15-bit pointer to the relative part.  START
	      (MAC24) contains the entire absolute address (code  =  1)  or
	      the absolute part of the relative address (code = 2).
	
	  5.  Obtains   the   user-specified   version   number   (.VERSION
	      directive)  from  UVER  (MAC24).   LINK  does  not  use  this
	      information.

	  6.  Obtains the  current  patch  level  of  MACREL  from  PTCHLOC
	      (HEADING in MAC24).



     2.3.5  FINIO (Macio)

     The FINIO subroutine reinitializes the binary  output  file's  control
     parameters.   This  allows  FIN2  to send the Loader Symbol Dictionary
     (LSD) preface and data to the area reserved for it at the beginning of
     the  binary output file.  Remember that the binary data (text) is sent
     to the output file first and the file  is  closed.   FIN2  then  calls
     routines  that  send  the  LSD  directly  to the file via calls to the


				     2-19
			  DESCRIPTIONS OF THE MODULES


     device handler.  The file is not explicitly opened via a call  to  the
     USR.

     Although logically part of FIN2, FINIO resides in MACIO due  to  space
     limitations.

     FINIO is called by FIN2 after it has closed the  binary  output  file.
     It performs the following tasks:

	  1.  Stores OUTLOC, which is the  starting  block  of  the  binary
	      file,  in  OUTREC  so  that  the  LSD  will  be stored at the
	      beginning of the binary file.

	  2.  Stores zeros in OUTSIZ and HOLSIZ to indicate to  the  output
	      routine  (PUTBUF  in  MACIO) that there is enough room in the
	      output file.

	  3.  Initializes the output buffer pointer (OPTR1)  to  the  first
	      location in the output buffer (contents of OUTBUF+1 ).

	  4.  Zeros FLGFLG to indicate that no flag field  is  to  be  sent
	      with the LSD.

	  5.  Zeros HDRWRD to specify in the block header that this  is  an
	      LSD block.  (0 means LSD, 4000 means text.)



     2.4  FIN3 (Overlays 11 and 13)

     FIN3 formats the symbol table printout, sends it to the listing  file,
     and closes the listing file.  It is called at the end of pass 3.

     The module consists of two overlays:  Overlay 13,  the  main  overlay,
     loads  into  the  Extremities Overlay Area;  Overlay 11, the auxiliary
     overlay, loads into the Directives Overlay Area.

     FIN3 is segmented  into  subroutines  primarily  because  of  boundary
     restrictions  on  the  PDP-8's  memory pages (most of the routines are
     called only once).  Consequently,  the  following  description  treats
     FIN3 as if it were a single logical entity.



     2.4.1  Unlabeled Routine (Overlay 11)

     This is an unlabeled routine that consists of  the  node  that  begins
     with  the overlay number 11 and ends at the label STPRNT.  It performs
     the following tasks:

	  1.  Loads the extension overlay (Overlay 11) into memory.

	  2.  Sets LISTWD to 0 to prevent the  creation  of  a  listing  by
	      overriding any program-initiated request.

				     2-20
			  DESCRIPTIONS OF THE MODULES


	  3.  Scans all the buckets, and links and creates a  single  large
	      bucket  (Bucket A) that contains all the symbol table entries
	      in alphabetical  order.   This  improves  the  efficiency  of
	      printing  the symbol table although pass 4 processing becomes
	      somewhat more inefficient.  Since the  bucket  pointers  that
	      follow   Bucket  A  are  still  present,  pass  4  efficiency
	      decreases only when the symbols that are added during pass  4
	      are  processed.   Notice that the permanent symbols remain in
	      the chain, because the chain must be intact for pass 4.

	  4.  Calculates the number of columns of symbol table  entries  to
	      print  by  adding 8 to WIDTH (number of columns on the output
	      device) and then dividing the result by  32  (decimal).   The
	      remainder  is  the  number of columns.  Since not more than 7
	      columns are allowed, the routine takes the result  modulo  8.
	      If  the number is 0, it uses 1 column.  Otherwise, it uses up
	      to 7 columns.  It stores the number of columns  to  print  in
	      COLNUM.

	  5.  Formats each page so that the symbol  table  entries  can  be
	      printed  in  alphabetical order and in columns rather than in
	      rows.  To do this, it  creates  an  auxiliary  array,  called
	      PTRTBL  which, though dimensioned at 8, can contain from 1 to
	      7 pointers;  one pointer for each column of the page.

	      As an example, the third pointer in PTRTBL is the pointer  to
	      the  chunk  that contains the first symbol name to be printed
	      at the top of the third column in  the  listing.   A  pointer
	      value  of  0  means  that  there  is no item to print in this
	      position.

	      It sets up these pointers as follows:

	      a.  Scans the symbol table beginning with the first chunk  to
		  be printed on the current page.

	      b.  Maintains, during the scan, a  count  of  the  chunks  to
		  determine which chunk will begin the next column.

	      c.  Stores the pointer to the 55th chunk in PTRTBL  when  the
		  chunk count reaches 54 (decimal).

	      d.  Ignores, during the count, permanent,  FIXTAB,  or  local
		  symbols  (bits  2  or  4  set  to 1 in their flag words).
		  These symbols are not  to  appear  in  the  symbol  table
		  listing.

		  (Notice that the last chunk computed is the  first  chunk
		  to be printed on the next page.  Its pointer is stored in
		  SYMNUM, not in PTRTBL.)

	      e.  Waits until a full page of pointers is set up  in  PTRTBL
		  and  stores  a  0 as the final entry (which is why PTRTBL


				     2-21
			  DESCRIPTIONS OF THE MODULES


		  has room for 8 entries).  It then calls STPRNT  to  print
		  this page of the symbol table.

	  6.  Passes control to location DLUP to format and print the  next
	      page  after  the  page  is  printed,  and  if there are still
	      symbols left to print.

	  7.  Inserts a CTRL/Z into the buffer when there are no more pages
	      to  print,  it fills the remaining buffer space (less 1) with
	      NULs to send the  contents  of  the  buffer  to  the  listing
	      device.

	  8.  Calls CLOSO (MACIO) to close the listing file.

	  9.  Branches to NEX (MAC24) to proceed to the next pass.



     2.4.2  STPRNT (Overlay 11)

     The routine STPRNT prints  a  physical  page  of  symbol  table  text.
     Pointers  in  PTRTBL  point  to the symbol table chunks containing the
     symbols that begin the top of each listing  column.   STPRNT  performs
     the following tasks:

	  1.  Calls NEWPAG (MAC3R) to begin a new page, and increments  the
	      sub-page number (SUBPAG) by 1.

	  2.  Loops 54 (decimal) times, once for each row (line) of text on
	      the  page.  During each iteration, it scans PTRTBL to get the
	      chunk pointers for each symbol in the row.  For each  column,
	      it performs the following tasks:

	      a.  Branches to ENDROW if the chunk pointer is 0  (end-of-the
		  row).

	      b.  (if the chunk pointer is not 0)  Copies  the  information
		  for  that  symbol  into the symbol table work area (NAME1
		  through QUAL in MAC24) and calls PRN to  print  the  name
		  the symbol.

	      c.  Prints a TAB, then calls XPRINT to print  the  additional
		  information associated with this symbol name.

	      d.  Zeros the symbol's current location counter (PC)  if  the
		  entry is a program section name.  If it is an .ASECT, the
		  routine sets the symbol's low PC to -1.

	      e.  Replaces the current chunk pointer in  PTRTBL,  with  the
		  pointer to the next chunk for this column.  It skips both
		  local and permanent symbols.  It inserts 0 if  there  are
		  no more chunks for this column.

	      f.  Advances to the next column.

				     2-22
			  DESCRIPTIONS OF THE MODULES


	  3.  Exits if it encounters a 0 as  the  first  entry  in  PTRTBL,
	      because  there  are  no  more  symbol table entries to print.
	      Otherwise, it prints a RETURN/IF sequence and decrements  the
	      loop counter (KNT).

	  4.  Processes the next row (step 2) if the value of  KNT  is  not
	      zero.   If KNT is zero, this is the last row on this page and
	      STPRNT returns control to the caller.



     2.4.3  PRNT2 (Overlay 11)

     The routine PRNT2 sends the two 6-bit characters  in  the  AC  to  the
     listing  file.   It calls PRNT6 twice;  once to print the character in
     the left byte and once to print the character in the right byte.



     2.4.4  PRN (Overlay 13)

     The routine PRN prints a symbol name.  If the first word of  the  name
     (NAME1 of the symbol table work area) is negative, it removes the sign
     bit from NAME1 and prints a dollar sign($) followed by the  name.   If
     NAME1  is  positive,  it  prints  the  name  by  itself.  PRN performs
     successive calls to PRNT2 to do the actual printing.



     2.4.5  XPRINT (Overlay 13)

     The routine XPRINT prints  a  symbol's  binary  value  and  associated
     qualifying  information.   It  performs  according  to  the  following
     conditions:

	  1.  If the symbol is in the Loader  Symbol  Dictionary  (LSD)  so
	      that bit 9 of its flag word = l, control passes to one of the
	      four routines listed below.  This depends on  the  LSD  entry
	      type  specified in bits 10-ll of the flag word.  Entry types,
	      destinations and tasks are shown in Table 2-4.

	  2.  If the symbol is a macro name (.MACRO), XPRINT:

	      a.  Changes the value word (which has been moved  to  PRTVAL)
		  to  0.   It  does not change SYMVAL, because its contents
		  may be written back into the symbol table later.

	      b.  Prints an M before the symbol's value (0000).

	  3.  If the symbol is not one  of  the  types  covered  above,  it
	      prints a space before the symbol's value.




				     2-23
			  DESCRIPTIONS OF THE MODULES


				   Table 2-4
	 Loader Symbol Dictionary Entry Types, Destinations, and Tasks

     ----------------------------------------------------------------------
     |	Entry Type   |		     Destination and Task		  |
     |---------------|----------------------------------------------------|
     |		     |							  |
     |	     0	     | XENTRY and prints an E  (.ENTRY)  before  printing |
     |		     | the symbol's value.				  |
     |		     |							  |
     |	     1	     | XGLOB and prints a  G  (.GLOBAL)  before  printing |
     |		     | the symbol's value.				  |
     |		     |							  |
     |	     2	     | XEXT and prints an X (.EXTERNAL) or a Y  (.SECREF) |
     |		     | before  printing four asterisks (****) in place of |
     |		     | the symbol's value.				  |
     |		     |							  |
     |	     3	     | XZTE and prints a Z (.ZTERNAL) before  printing  a |
     |		     | zero  followed  by three asterisks (0***) in place |
     |		     | of the symbol's value.				  |
     ----------------------------------------------------------------------


	  4.  If the symbol is undefined (flag word is negative), it  calls
	      UNDF, which:

	      a.  Prints four asterisks followed by a left arrow (****<-- )
		  and a TAB in place of a value.

	      b.  Exits from the routine.

	  5.  If the symbol is defined, it calls OPRINT  (MAC30)  to  print
	      the  value  of  the  symbol  as  a  4-digit octal number with
	      leading zeros.

	  6.  If the symbol is a .SECT name, it prints two spaces  and  the
	      type  of  sect  (.ASECT,  .RSECT,  .FSECT, .DSECT, .ZSECT, or
	      .XSECT) to the right of the value.  It  obtains  the  program
	      section  type from bits 6-8 of the flag word, then exits from
	      the routine.

	  7.  If the symbol is not a .SECT name (flag bits 6-8 are  0),  it
	      branches  to NOTSCT, which performs a branch depending on the
	      symbol's type (bits 9-11 of the flag word).

	      a.  If the symbol is  a  .MACRO  name,  pseudo-macro,  MACREL
		  directive,  .EXTERNAL, .ZTERNAL, or absolute (implicit or
		  explicit .ASECT), it prints a TAB and exits.

	      b.  If the symbol is  a  .ENTRY  name,  a  .GLOBAL  name,  or
		  resides  in a relocatable program section, its value must
		  be displayed in relation to the beginning of the  program
		  section.   To show this, XPRINT prints a plus sign (+), a
		  space, and the name of  the  program  section  where  the

				     2-24
			  DESCRIPTIONS OF THE MODULES


		  symbol  resides.   Following  this, it prints a TAB, then
		  exits.



     2.4.6  PRNT6 (Overlay 13)

     The routine PRNT6 sends the 6-bit ASCII character in  the  right  (low
     order)  byte of the AC to the listing file.  It automatically converts
     MACREL's internal codes for dollar sign (33) and period (44) to  their
     6-bit  equivalents  (44  and 56 respectively).  It calls (QQ)LISTER to
     print the appropriate ASCII character.



     2.5  MACERR (Special Overlay)

     The MACERR module is the error message overlay.  It contains both  the
     routines  that  print  the  error messages and the error message text.
     This is a special overlay in the sense that it is  not  loaded  via  a
     call  to LOAD like the other MACREL overlays.  Instead, when a routine
     detects an error, it performs a  subroutine  jump  to  ERROR  (MAC24),
     which loads MACERR and passes control to ERRTN.


				    CAUTION

		    MACERR must always be exactly 23 blocks
		    long to allow ERROR to perform overlay
		    address computation.


     ERRTN uses the address of the error call to find and print the  actual
     error message text as follows:

	  1.  Obtains the address of the call (JMS), and  searches  for  an
	      entry  in  a table (ERLST) that contains the addresses of all
	      error calls.

	  2.  Finds the matching address in the table and  then  calculates
	      the  ordinal position of that entry from the beginning of the
	      table.

	  3.  Uses this value to  index  into  the  message  pointer  table
	      (MESLST)  and  obtain  a  pointer  that is the 12-bit virtual
	      address of the  desired  error  message  in  MACREL.SV.   The
	      pointer is the message's address that is assigned at assembly
	      time.  (Error message pointers have virtual addresses in  the
	      range 3400-7377.)

	  4.  Calculates the block number in MACREL.SV  where  the  message
	      resides  and  reads  this  block into a buffer that begins at
	      memory location 10400.  (Table  2-5  shows  the  relationship


				     2-25
			  DESCRIPTIONS OF THE MODULES


	      between  the block numbers in MACREL.SV and MACERR's assembly
	      time addresses.)

	  5.  Calculates exactly where an  error  message  resides  in  the
	      buffer (block).

	  6.  Prints the message on either  the  terminal,  the  BATCH  log
	      device,   or  in  the  listing,  using  the  output  routines
	      described in Table 2-6.

	  7.  Returns control to ERROR, when MACERR finishes to restore  to
	      memory the five blocks that it swapped out.  (It is important
	      that these blocks never contain code that calls ERROR.)

				   Table 2-5
		       Layout of MACERR Within MACREL.SV

		 --------------------------------------------		
		 | Relative |	       |   Assembly-time    |
		 |  Block   | Contents | Addresses (MACERR) |
		 |----------|----------|--------------------|
		 | 101-104  |	code   |   51000-52777	    |
		 | 105	    |  unused  |  (53000)	    |
		 | 106	    |    :     |   53400  ERRBLK+6  |
		 | 107	    |    :     |   54000	    |
		 | 110	    | message  |   54400	    |
		 | 111	    |   text   |   55000	    |
		 | 115	    |    :     |   55400	    |
		 | 113	    |    :     |   56000	    |
		 | 114	    |    :     |   56400	    |
		 | 115	    |    :     |   57000  ERRBLK+15 |
		 | 116-122  |	       |   60000-62377 *    |
		 --------------------------------------------		
	* These are the five blocks that are swapped to and from the swap
	area located at addresses 10400-12777 during run time.



     2.5.1  Error Typeout Routines

     MACERR contains the output routines listed in Table 2-6.


				   Table 2-6
			 MACERR Output Routine Summary

     ----------------------------------------------------------------------
     |	Name  |			     Task				  |
     |--------|-----------------------------------------------------------|
     |	      |								  |
     | TYPERR | Types error message  on  error  log  (TTY  or  BATCH  log |
     |	      | file).							  |
     ----------------------------------------------------------------------
						 (continued on next page)

				     2-26
			  DESCRIPTIONS OF THE MODULES


			       Table 2-6 (Cont.)
			 MACERR Output Routine Summary

     ----------------------------------------------------------------------
     |	Name  |			     Task				  |
     |--------|-----------------------------------------------------------|
     | PRCHR  | Prints  single  characters  on  a  device  specified   by |
     |	      | OUTDEY.   (The  AC  will be non-zero when PCHR returns to |
     |	      | the caller.)						  |
     |	      |								  |
     | PRNAM  | Prints a  6-character  name  on  a  device  specified  by |
     |	      | OUTDEY.  (The AC will be non-zero when PRNSM  returns  to |
     |	      | the caller.)						  |
     |	      |								  |
     | PR6A   | Prints a 6-bit ASCII character on a device  specified  by |
     |	      | OUTDEY, ignoring NULs.					  |
     |	      |								  |
     | SETNAM | Sets up name to be printed by PRNAM;   followed  by  CDF, |
     |	      | then PTR.						  |
     |	      |								  |
     | PR     | Prints a character on the error log device if  CTRL/O  is |
     |	      | not  in  effect.  Also checks for CTRL/O, CTRL/C, CTRL/S, |
     |	      | and the E, F, and L options.				  |
     |	      |								  |
     | TPUT   | Types a character unconditionally on the error log device.|
     |	      |								  |
     | TP     | Types a character unconditionally on the terminal.	  |
     |	      |								  |
     | PR2    | Prints two 6-bit ASCII characters using PR.		  |
     |	      |								  |
     | PRO    | Prints one 6-bit ASCII character using PR.		  |
     |	      |								  |
     | PR12   | Prints one 12-bit number as 4 octal digits using PR.	  |
     |	      |								  |
     | STNAM  | Sets up a symbol table name for printing, and obtains the |
     |	      | value of the symbol in VAL.				  |
     |	      |								  |
     | CHKKBD | Checks to see if CTRL/C, CTRL/S, CTRL/O, E, F, or  L  was |
     |	      | typed on the keyboard.					  |
     |	      |								  |
     | OUTDEY | Contains either PR or LPUT,  as  set  up  by  TYPERR  and |
     |	      | PRNERR.							  |
     |	      |								  |
     | CRLFF  | Prints carriage return/linefeed on OUTDEY.		  |
     |	      |								  |
     | TYPE   | Prints a 6-bit ASCII character (carriage return/line feed |
     |	      | if NUL character) on a device specified by OUTDEY.	  |
     ----------------------------------------------------------------------



     2.5.2  Creating New Error Messages

     The following rules describe how to create new error messages.

				     2-27
			  DESCRIPTIONS OF THE MODULES


	  1.  The calling routine must:

	      a.  Make sure that the data field is set to  the  data  field
		  here the routine resides.

	      b.  Perform a call to ERROR as follows:

		  ERnnn, JMS QQERROR

	      where:

	      ERnnn  is  a  defined  as  a  global  symbol  in  the  global
	      definition file MGLOB.MA

	  2.  The error address table, ERLST, must contain an entry that is
	      the  negated  address  value  of  the location of the call to
	      ERROR.  A -1 ends this table.  The form of the entry is:

		   .EXTERNAL ERnnn -ERnnn

	  3.  The message pointer table, MESLST, must contain an entry that
	      is  in  the same relative position as its corresponding entry
	      in ERLST.  (The pointers are grouped by module.)

	  4.  The error message table must contain a message in the form:

		   adr pass TEXT /xx msg/

	      where:

		   adr	    is the address of the fixup routine (This is  a
			    routine   that   can   be   called  to  perform
			    preprocessing  before  the  error  message   is
			    printed.   If  this  entry  is 0, no routine is
			    called.)

		   pass	    is the number of the physical  pass  where  the
			    error was detected

		   xx	    is the two-character error message code

		   msg	    is the text of the error message

     The pass number represents the physical (not logical) pass  number  on
     which  this error message should be given.  For example if there is no
     binary requested, then the listing pass is physical pass 2 even though
     it  is logical pass 3.  No message is given if this is the wrong pass.
     The assumption is that the message  has  already  been  printed  on  a
     previous pass.  This avoids message duplication.

     For errors that are pass independent, such as I/O errors, MACREL  uses
     the  pass  number code 4000.  These messages are printed regardless of
     which pass is in effect.


				     2-28
			  DESCRIPTIONS OF THE MODULES


     Two special codes are permitted within the text of the error message:

	  #   Print the symbol name that is in NAME1 through NAME3  of  the
	      symbol  table  work  area  (MAC24) at this point in the error
	      message.

	  ?   Print the character enclosed in quotes residing  in  CHAR  at
	      this point in the error message.



     2.5.3  Number of Errors Detected

     In order to print the number of errors  detected,  FIN0  simulates  an
     error at the end of the assembly using ER230 (FIN0).  The ER1 (MACERR)
     routine prints the ERRORS  DETECTED  message  if  necessary  and  then
     returns to the address immediately following the ER230 label.



     2.6  MACEXP

     The module MACEXP contains the memory-resident routines  that  perform
     expression parsing.  It consists of the main routine EXPR and a number
     of subordinate routines.  MACEXP loads its extension overlay,  EXPOVR,
     only as needed.



     2.6.1  EXPR

     EXPR is the controlling routine for expression parsing.  Routines call
     EXPR  to  parse  an expression beginning with the current character in
     the input stream.  The call to EXPR is:

	  JMS I (QQEXPR

     Control returns to the caller at the address stored in EXPR  with  the
     absolute  (12-bit)  part of the expression in the accumulator (AC) and
     the relative part of the expression in EXPREL (15-bit pointer).

     EXPR operates recursively.  Before it calls itself, it saves the local
     variables  listed in Table 2-7 on the expression stack (EXPSTK).  When
     it returns from the (recursive) call, it removes these variables  from
     the stack and restores EXPR to its previous operational state.

     EXPR performs the following tasks.

	  1.  Sets the variables PRVOPR,  EXPABS,  EXPREL,  and  EXPCOD  to
	      zero.   This  specifies  that no previous binary operator has
	      been found and that the initial value of the expression is 0.

	  2.  Calls TERM to obtain and evaluate a term of the expression.


				     2-29
			  DESCRIPTIONS OF THE MODULES


				   Table 2-7
		 Local Variables Saved on the Expression Stack

     ----------------------------------------------------------------------
     |	 Name	|			Use				  |
     |----------|---------------------------------------------------------|
     |		|							  |
     |  EXPABS  | Absolute part of total expression computed so far	  |
     |		|							  |
     |  EXPCOD  | Relocation type:					  |
     |		|		   -1 = Value of expression is top entry  |
     |		|			on LINK's stack.		  |
     |		|		    0 = Simple relocation; add absolute	  |
     |		|			part to relative part		  |
     |		|		    1 = .FSECT relocation		  |
     |		|		    2 = CDF relocation; add field of	  |
     |		|			relative part, multiplied by 10	  |
     |		|			(octal) to absolute part	  |
     |		|							  |
     |  EXPR	| Return address from EXPR				  |
     |		|							  |
     |  EXPREL  | Relative part of result of total expression so far	  |
     |		| computed						  |
     |		|							  |
     |  TERM	| Return address from TERM				  |
     |		|							  |
     |  UNARYM  | Number of minuses seen on term to be combined with	  |
     |		| expression result					  |
     |		|							  |
     |  PRVOPR	| Previous operator;  used to combine new value with old  |
     |		| result						  |
     ----------------------------------------------------------------------


	  3.  (if it cannot perform the requested binary operation)

	      a.  Calls HARD to set up loader codes that  request  LINK  to
		  perform the operation.

	      b.  Obtains the next operator and stores its code  in  PRVOPR
		  (see Table 2-7).

	      c.  Calls TERM again (step 2 above).

	  4.  (if it can perform the  requested  binary  operation)  Passes
	      control  to  the  routine  specified by the code in PRVOPR to
	      process the previous operator (see Table  2-8).   On  return,
	      the results reside in EXPABS, EXPREL, and EXPCOD.







				     2-30
			  DESCRIPTIONS OF THE MODULES


				   Table 2-8
		     EXPR Previous Operator Dispatch Table

     ----------------------------------------------------------------------
     | Code |	 Operator    | Processing Routine |	     Use	  |
     |------|----------------|--------------------|-----------------------|
     |	0   | NUL	     | NOPREV		  | No previous operator  |
     |	1   | +		     | ADD		  | Addition		  |
     |	2   | -		     | SUB		  | Subtraction		  |
     |	3   | ^		     | MUL		  | Multiplication	  |
     |	4   | %		     | DIV		  | Division		  |
     |	5   | <space> or TAB | OR		  | Logical inclusive OR  |
     |	6   | &		     | ANDY		  | Logical AND		  |
     |	7   | !		     | SHIFT		  | 6-bit left shift	  |
     |	10  | !		     | OR		  | Logical inclusive OR  |
     ----------------------------------------------------------------------



     2.6.2  TERM

     The routine TERM parses and evaluates a term from  the  current  input
     stream.  The calling sequence is:

	  JMS	  TERM
		  address if term is empty
		  address for normal return

     It  scans  all  characters  and  passes  control  to  the  appropriate
     processing  routine  listed in Table 2-9.  It skips over spaces and if
     the term is empty, returns control to the caller at the  first  return
     address.   Control  normally  returns  to  TRM's  caller at the second
     return address.


				   Table 2-9
			 TERM Character Dispatch Table

     ----------------------------------------------------------------------
     |	 Character   |Processing|		  Function		  |
     |		     | Routine  |					  |
     |---------------|----------|-----------------------------------------|
     |		     |		|					  |
     | A - Z, a - z  |	SYMM	| Parses a symbol period (.), performs  a |
     | and comma (,) |		| symbol  table  lookup,  and  exits from |
     |		     |		| TERM.					  |
     |		     |		|					  |
     | 0 - 9	     |  NUMBR	| Parses a number and exits from TERM.	  |
     |		     |		|					  |
     | -	     |  UNOPM	| Increments the  minus  sign  count  and |
     |		     |		| reiterates TERM.			  |
     ----------------------------------------------------------------------
						 (continued on next page)


				     2-31
			  DESCRIPTIONS OF THE MODULES


			       Table 2-9 (cont.)
			 TERM Character Dispatch Table

     ----------------------------------------------------------------------
     |	 Character   |Processing|		  Function		  |
     |		     | Routine  |					  |
     |---------------|----------|-----------------------------------------|
     | (	     |  PENP	| Parses   a   current    page    literal |
     |		     |		| (including   the   right  parenthesis), |
     |		     |		| performs a  symbol  table  lookup,  and |
     |		     |		| exits from TERM.			  |
     |		     |		|					  |
     | [	     |  OPENB	| Parses a page zero  literal  (including |
     |		     |		| the  right  square bracket), performs a |
     |		     |		| symbol table  lookup,  and  exits  from |
     |		     |		| TERM.					  |
     |		     |		|					  |
     | "	     |  DBLQ	| Parses an expression of the form:   'A, |
     |		     |		| where  A  is  a  single  character.  It |
     |		     |		| inserts the 8-bit ASCII  code  for  the |
     |		     |		| character  in TRMABS if bit 4 of ENABWD |
     |		     |		| is set to a 1, then exits from TERM.	  |
     |		     |		|					  |
     | '	     |  SNGLQ	| Parses an expression of the form:  "AB, |
     |		     |		| where  A  and  B are single characters. |
     |		     |		| It inserts the 6-bit ASCII code  for  A |
     |		     |		| in  bits  0 - 5  of TRMABS and the code |
     |		     |		| for B in bits 6 - 11  of  TRMABS,  then |
     |		     |		| exits from TERM.			  |
     |		     |		|					  |
     | ^	     |  UPAROW	| Parses  the  temporary  radix   control |
     |		     |		| operators  (^B,  ^D,  ^O  and  ^")  and |
     |		     |		| their arguments, then exits from TERM.  |
     |		     |		|					  |
     | +	     |  TRM1	| Skips over spaces and  tabs  (HT)  then |
     |		     |		| branches  to  the  appropriate  routine |
     |		     |		| depending on the next character.	  |
     |		     |		|					  |
     | <	     |  OPENA	| Evaluates an  expression  of  the  form |
     |		     |		| <expression>  by  performing  recursive |
     |		     |		| calls to EXPR.  If  the  expression  is |
     |		     |		| absolute,  it checks to see if a dollar |
     |		     |		| sign ($) follows.  If this is true,  it |
     |		     |		| branches  to  OTSYM.   If  this  is not |
     |		     |		| true, it branches to PREFIX to  perform |
     |		     |		| a  unary minus operation on the current |
     |		     |		| term.					  |
     |		     |		|					  |
     | >	     |  VACTRM	| Causes an exit from TERM to  the  first |
     |		     |		| address  following the call (empty term |
     |		     |		| address).				  |
     ----------------------------------------------------------------------
						 (continued on next page)


				     2-32
			  DESCRIPTIONS OF THE MODULES


			       Table 2-9 (cont.)
			 TERM Character Dispatch Table

     ----------------------------------------------------------------------
     |	 Character   |Processing|		  Function		  |
     |		     | Routine  |					  |
     |---------------|----------|-----------------------------------------|
     | other	     |		|					  |
     | characters    |  ER22	| Calls the  error  routine  to  send  an |
     |		     |		| error  message  for illegal characters, |
     |		     |		| then branches to TRM1.		  |
     ----------------------------------------------------------------------



     2.7  MACINI

     The module MACINI contains MACREL's initialization routines.  This  is
     once-only  code that resides in I/O buffer and overlay space.  Control
     passes to ONCE from NIXT (MAC24) immediately after MACREL is started.


     2.7.1  DATE

     The DATE routine obtains the OS/8-stored system date, converts it to a
     printable  string,  and  stores  it  (one  character  per word) in the
     listing header buffer.  If no OS/8 date  was  entered,  it  fills  the
     buffer  with  blanks.   The  date resides in absolute memory locations
     17666 and 07777 (bits 3 and 4).  Table 2-10 shows the internal storage
     format.


				  Table 2-10
		  Internal Storage Format of OS/8 Date Words

     ----------------------------------------------------------------------
     |	Location    |  Bits  | Value Range |	      Use		  |
     |		    |	     |	 (octal)   |				  |
     |--------------|--------|-------------|------------------------------|
     |		    |	     |		   |				  |
     |	17666	    |  0-3   |	  1-14	   | Month (Jan. through Dec.)	  |
     |		    |  4-8   |	  1-37	   | Day of Month		  |
     |		    |  9-11  |	  0-7	   | Year-1970 (modulo 8)	  |
     |		    |	     |		   |				  |
     |	07777	    |  3-4   |	  0-3	   | (Year-1970)/8		  |
     ----------------------------------------------------------------------

     The format for the converted date is:

	  dayname dd-mon-yy

     where:



				     2-33
			  DESCRIPTIONS OF THE MODULES


	  dayname    is the 3-character abbreviation of the name of the day
		     (Monday through Sunday)

	  dd	     is the day of  the  month  (1  through  31  (decimal))

	  mon	     is the 3-character abbreviation for the  name  of  the
		     month (Jan.  through Dec.)

	  yy	     is the least significant  digits  of  the  year  (1970
		     modulo 8)



     2.7.2  ONCE

     The ONCE routine performs the following tasks:

	  1.  Interrogates the locations that  contain  the  user-specified
	      options to the Command Decoder.

	  2.  Sets various option-related flags.

	  3.  Moves a copy of the option settings to  SWATOL,  SWMTOX,  and
	      SWYTO9  in  Field 0 (MAC24) so they can be referenced without
	      executing CDF instructions.



     2.7.3  CORE

     The CORE routine determines the  real  physical  size  of  memory  and
     returns to ONCE with the size value in the AC.



     2.7.4  LIMSET

     The LIMSET routine sets up the memory limit table (LIMTBL) to  specify
     the portions of memory that are available for symbol table allocation.
     This is a table of eight 2-word entries;  one  entry  for  each  field
     that  MACREL  can  use  (see  Figure 2-1).  The first word of an entry
     specifies the lower memory limit  for  the  field.   The  second  word
     specifies  the  first  address that is not available in the field.  It
     sets the first word of an entry to -l to indicate that this field  and
     all higher fields are unavailable.

     To set up the table, LIMSET must determine whether:

	  o  BATCH is running

	  o  there is a one/ or two page system handler

	  o  the system handler is TD8E (Simple DECtape)


				     2-34
			  DESCRIPTIONS OF THE MODULES


		   Word
		         -----------------------------------
		    0    |    Field 0 low address limit    |
			 |---------------------------------|
		    1	 |    Field 0 high address limit   |
			 |---------------------------------|
		    .	 |		   .		   |
		    .	 |		   .		   |
		    .	 |		   .		   |
			 |---------------------------------|
			 |    Field 7 low address limit    |
			 |---------------------------------|
		   15	 |    Field 7 high address limit   |
			 -----------------------------------
						   ML-029-80

		Figure 2-l  Memory Limit Table (LIMTBL) Layout


	  o  the Y option was selected

	  o  there is more than 12K words of memory (If there  is  not,  it
	     automatically sets the Y option.)



     2.7.5  PREFORM

     The PREFORM routine formats all memory not used by MACREL into  8-word
     chunks.   It  chains  these chunks together using 15-bit pointers (see
     Section 1.5.2).  The first word in each chunk is a 15-bit pointer that
     points to the next chunk in the chain.  It deposits the pointer to the
     first chunk in the chain into location FREESPACE.  A  forward  pointer
     of 0 marks the last chunk in the chain.


				     NOTE

		   The initial symbol table is not in chunk
		   format  and  is  designed not to use any
		   pointer  addresses.   This  is   because
		   PREFORM  formats over the initial symbol
		   table without destroying it.



     2.7.6  SYMINI

     The SYMINI routine builds the run-time symbol  table  using  FREESPACE
     chunks and the symbols contained in the initial symbol table (SYMTAB).
     It uses the global routines (QQ) LOOKUP, (QQ)  ENTER,  and  (QQ)PUTSYM
     routines  to  insert  the  permanent  symbols into the run-time symbol
     table.  The initial symbol  table  consists  of  a  number  of  8-word
     entries  as  described  in Table 2-11.  SYMINI reads each entry in the

				     2-35
			  DESCRIPTIONS OF THE MODULES


     initial symbol table (SYMTAB) and  determines  whether  the  entry  is
     affected by the A, O, Q, or R options.


				  Table 2-11
		       Initial Symbol Table Entry Format

     ----------------------------------------------------------------------
     | Word |			     Use				  |
     |------|-------------------------------------------------------------|
     |	    |								  |
     |	 0  | Unused							  |
     |	    |								  |
     |	 1  | = 4000 - PDP-8/A or PDP-8/E specific symbol (A command	  |
     |	    |	       option)						  |
     |	    | = 0100 - Redundant (unnecessary) symbol (R command option)  |
     |      | = 0200 - EAE symbol (Q command option)			  |
     |      | = 1000 - Directive that pertains to macros (O command	  |
     |	    |	       option)						  |
     |	    |								  |
     |   2  | char 0 / char 1	   char = character of symbol name	  |
     |	 3  | char 2 / char 3 		  in MACREL 6-bit code.		  |
     |	 4  | char 3 / char 5						  |
     |	    |								  |
     |   5  | Symbol value or address depending on word 6		  |
     |	    |								  |
     | * 6  | = 0000 - Regular symbol.  Word 5 contains symbol value and  |
     |	    |	       word 7 contains 0000.				  |
     |	    | = 0002 - Pseudo-macro.  Word 5 contains address of field 0  |
     |	    |	       processing routine and word 7 contains 0000.	  |
     |	    | = 0003 - Pseudo-operator.  Word 5 contains the address of	  |
     |	    |	       the processing routine located in the overlay	  |
     |	    |	       specified by the contents of word 7.		  |
     |	    | = 2000 - Memory reference instruction.  Word 5 contains	  |
     |	    |	       symbol value and word 7 contains 0000.		  |
     |	    |								  |
     |   7  | Overlay number						  |
     ----------------------------------------------------------------------
       * The codes in this word may be ORed together.


     SYMINI uses the (QQ)LOOKUP,  (QQ)ENTER,  and  (QQ)PUTSYM  routines  in
     MAC24 to insert the permanent symbols into the symbol table.



     2.8  MACIO

     The MACIO module contains the Field 1 resident input/output routines.






				     2-36
			  DESCRIPTIONS OF THE MODULES


     2.8.1  IOINIT and IONIT2

     These routines, although resident in MACIO, are logically part of  the
     FIN0 Overlay.  They are described in Sections 2.2.10 and 2.2.11.



     2.8.2  FINIO (MACIO)

     The FINIO subroutine reinitializes the binary  output  file's  control
     parameters.   This  allows  FIN2  to send the Loader Symbol Dictionary
     (LSD) preface and data to the area reserved for it at the beginning of
     the binary output file.  Remember that the binary data (text) is  sent
     to  the  output  file  first  and the file is closed.  FIN2 then calls
     routines that send the LSD directly to  the  file  via  calls  to  the
     device  handler.   The file is not explicitly opened via a call to the
     USR.

     FINIO is called by FIN2 after it has closed the  binary  output  file.
     It performs the following tasks:

	  1.  Stores OUTLOC, which is the  starting  block  of  the  binary
	      file,  in  OUTREC  so  that  the  LSD  will  be stored at the
	      beginning of the binary file.

	  2.  Stores zeros in OUTSIZ and HOLSIZ to indicate to  the  output
	      routine  (PUTBUF  in  MACIO) that there is enough room in the
	      output file.

	  3.  Initializes the output buffer pointer (OPTR1)  to  the  first
	      location in the output buffer (contents of (OUTBUF+1).

	  4.  Zeros FLGFLG to indicate that no flag field  is  to  be  sent
	      with the LSD.

	  5.  Zeros HDRWRD to specify in the block header that this  is  an
	      LSD block.  (0 means LSD, 4000 means text.)



     2.8.3  READOS

     READOS is a subroutine that reads characters from an OS/8 file.  It is
     called  by  GETOS  to  fill  the  input  buffer from the current input
     device.  Although it can use input buffers of  various  sizes,  buffer
     size  in  this  version of MACREL is limited to 2 blocks (a block is 2
     memory pages).  The buffer begins at INPBUF;  its length in blocks  is
     specified by INPLEN (MAC24).

     READOS performs the following tasks:

	  1.  Resets OS8PTR to point to the beginning of the  input  buffer
	      (the word before the first word of the next double word to be
	      read).

				     2-37
			  DESCRIPTIONS OF THE MODULES


	  2.  Determines how many blocks are left in the input file so that
	      nonexistent blocks are not read.

	      If there are fewer blocks remaining  than  are  specified  by
	      INPLEN,  the  subroutine  calls  READSHORT  to read the exact
	      number of blocks left in the current input file.

	      If the input device  is  not  block  (file)  structured,  the
	      subroutine reads the maximum number of blocks (INPLEN).

	  3.  Stores the actual number of blocks read in INSIZ.

	  4.  Subtracts INSIZ from INLEN if the device is not block  (file)
	      structured.   This  is  because  INLEN  specifies  the actual
	      number of blocks left to read from the input device.

	  5.  Sets RDSIZ and BUFKNT according to  the  contents  of  INSIZ.
	      BUFKNT  contains the negated number of double-words of actual
	      data in the OS/8 input buffer.  RDSIZ contains  the  function
	      control word passed to the input device handler.  Bits 6-8 of
	      this word contain a 1 to indicate that the input buffer is in
	      Field  1.  Bits 1-5 specify the number of pages of data to be
	      read.

	  6.  Calls the device handler (address is in INHNDLR)  to  perform
	      the read operation.

	  7.  Calls INERR to determine the nature of any error  it  detects
	      during  the  read  operation.   If  it  was  an  end-of-file,
	      operation    continues.      This     is     because     only
	      non-file-structured   device   handlers   return  end-of-file
	      errors.  These handlers always put a  CTRL/Z  in  the  buffer
	      after  the  data.   INERR  generates  the  appropriate  error
	      messages for all other I/O error conditions.

	  8.  Increments  INREC  by  the  value  of  INSIZ  when  the  read
	      operation is complete.  This is because INREC always contains
	      the number of the next block to read from the input device.



     2.8.4  SWITCH

     The routine SWITCH is the controlling routine of the  input  coroutine
     switching mechanism.  It is called with a single argument that follows
     the call.  The argument is a pointer to the new stream input routine.

     SWITCH performs the following tasks:

	  1.  Places the name of the current stream on the stream stack  so
	      that the specified stream becomes the new current stream.

	  2.  Sets up the following variables with  information  about  the
	      new stream.

				     2-38
			  DESCRIPTIONS OF THE MODULES


	      SGET	contains the address of the new stream.

	      SLOC	contains the address of the context block  for  the
			new stream.


	      SRET	contains the address of the partner  coroutine  for
			the new stream

	      SSTRT	contains the address of the beginning of  the  code
			for  the  new  stream.   (This  address becomes the
			initial value stored in the partner coroutine entry
			point.)

	  3.  Places all the local variables and SRET on the  stream  stack
	      if  the  contents  of SRET are non-zero.  (In this case, SRET
	      serves as a flag at the end of the  stack  to  indicate  that
	      local variables are stored on the stack.)

	  4.  Initializes SRET to the contents of SSTRT.   Notice  that  it
	      does not have to save local variables on the stack when a new
	      coroutine  is  entered  unless  that   coroutine   had   been
	      previously in use (that is, this call is recursive).



     2.8.5  SWBACK

     The routine SWBACK switches from the current input  coroutine  to  the
     previous  input  coroutine.   It  is  called  when  an input coroutine
     determines that it has reached the end of the current input stream and
     data  must  come  from the previous input stream.  Since IOINIT (FIN0)
     establishes ZGET as the initial input stream coroutine,  stream  stack
     underflow cannot occur.



     2.8.6  GETOS, and ORET Coroutines

     The GETOS routine gets 7-bit packed ASCII  characters  from  the  OS/8
     input  buffer  (INPBUF), unpacks them and sends each one via the AC to
     ORET.  It performs the following tasks:

	  1.  Forces the character to be 7-bit ASCII.

	  2.  Loads the character into  the  AC  and  returns  to  NEXTCHAR
	      (MAC24) if the character is not a CTRL/Z.

	  3.  Causes ORET to branch to EOF, which  performs  the  following
	      steps if the character is a CTRL/Z:

	      a.  Sets up the next input file and returns control to GETOS
		  to continue the process.


				     2-39
			  DESCRIPTIONS OF THE MODULES


	      b.  Calls SWBACK to make ZGET the  current  input  stream  if
		  there  is  no  further file input.  



     2.8.7  MGET and RGET Coroutines

     The MGET and RGET routines obtain characters that reside in the symbol
     table,  7  ASCII characters per chunk.  These characters are stored in
     7-bit ASCII.  The high-order bit (bit 0) of the word, ordinarily zero,
     is  a  special  flag  when  it  is non-zero.  Table 2-12 defines these
     symbol table flags.


				  Table 2-12
			Symbol Table Flags Definitions

     ----------------------------------------------------------------------
     |   Flag	       |	  Description				  |
     |-----------------|--------------------------------------------------|
     |  4000+n	       | argument marker for argument n			  |
     |	7770	       | end-of-macro-body marker			  |
     |	7771	       | end-of-argument marker				  |
     |	7772	       | end-of-repeat range marker			  |
     |	7773	       | argument   expression    indicator    (for    an |
     |		       | expression   that   occurs  within  a  substring |
     |		       | construct)					  |
     |	7774	       | argument symbol indicator  (for  a  symbol  that |
     |		       | occurs within a substring construct)		  |
     |	7775-7777      | reserved for future use			  |
     ----------------------------------------------------------------------



     2.8.8  ZGET

     The input coroutine ZGET always returns  CTRL/Z  codes.   It  prevents
     stream stack underflow.



     2.8.9  OFIX

     The routine OFIX re-fetches an OS/8 handler and re-reads an OS/8 input
     file  block as necessary when switching back to OGET.  This is to make
     sure that the desired handler was not overlaid by another handler left
     over from a previous pass.



     2.8.10  SPUSH

     The routine SPUSH is a general-purpose routine  that  places  (pushes)


				     2-40
			  DESCRIPTIONS OF THE MODULES


     the  contents  of  the  AC  on a standard pushdown stack.  The calling
     sequence is:

	  TAD value
	  JMS I [SPUSH
	  stackname

     where:

	  value       is the value to be saved (pushed) on the stack

	  stackname   is a pointer to the beginning of the stack

     The stack must reside in Field 1 and be of the following form:

	  stackname,  -length
		      elements
		      .
		      .
		      stack
		      area
		      .
		      .

     where:

	  stackname	is the name of the stack

	  -length	is a negative value that is the length of the stack
			area

	  elements	is the number of elements currently  on  the  stack
			(This value is initially 0.)

	  stack area	is the words that form the stack area itself



	2.8.11  SPOP

     The routine SPOP is a general-purpose routine that removes  (pops)  an
     entry  from a pushdown stack.  The stack must reside in Field 1 and be
     of the form described in Section 2.8.10.  SPOP returns control to  the
     calling routine with the "popped" stack entry in the AC.

     The calling convention is:

	  JMS I [SPOP
	  stackname

     where:

	  stackname	is a pointer to the beginning of the stack


				     2-41
			  DESCRIPTIONS OF THE MODULES


     2.8.12  LOCPSH

     The routine LOCPSH places (pushes) the coroutine  local  variables  on
     the stream stack.



     2.8.13  LOCPOP

     The routine LOCPOP removes (pops) the coroutine local  variables  from
     the stream stack.



     2.8.14  OFETCH

     The routine OFETCH loads an OS/8 handler into memory.



     2.8.15  PUTBUF

     The routine PUTBUF sends the full output buffer (OUTBUF) of characters
     to  the listing file one block at a time.  Although it can use buffers
     of various sizes, the size of the output buffer  in  this  version  of
     MACREL is limited to 2 blocks (a block is 2 pages).  The buffer begins
     at OUTBUF.  Its length in blocks is specified by OUTLN (MAC24).



     2.8.16  LISTOR, LSTRET, and OUTLST

     The coroutines LISTOR, LSTRET,  and  OUTLST  send  characters  to  the
     output  file on odd passes.  They use the standard OS/8 packing scheme
     to fill the output buffer with characters (see the MACREL/LINK  User's							___________________
     Manual).   On  even  passes,  no packing is required, so PUTBUF can be     ______
     called directly.



     2.8.17  CONV

     The routine CONV converts a 15-bit pointer into a CDF instruction  and
     a  12-bit  address.   Upon  entry, the AC contains the 15-bit pointer.
     CONV creates a CDF instruction to the  appropriate  field  and  stores
     this  CDF  at  the  location specified by the first argument.  It then
     loads the 12-bit address to the first word of the chunk  into  the  AC
     and passes control to the calling routine.



     2.8.18  DELETE

     The routine DELETE deletes a string of characters  from  macro  space.

				     2-42
			  DESCRIPTIONS OF THE MODULES


     Before  calling  this routine, you must set up two words, DE1 and DE2.
     DE1 points to the first chunk to be deleted, and  DE2  points  to  the
     last chunk to be deleted.



     2.8.19  LOOKU

     The routine LOOKU looks up a file on the device.   The  file  name  is
     specified  in  locations  NAME1 through NAME4 of the symbol table work
     area (MAC24).  The device number resides in the AC.  Upon  return,  FN
     contains  the  starting  block  number  and  LOOKLN  contains the file
     length.  LOOKU is called by the  $INCLUDE  (OVRE)  and  LNKCHN  (OVRT)
     routines.



     2.8.20  ZINIT

     The routine ZINIT initializes the state of the macro processor at  the
     beginning of each pass.



     2.9  MACLIT (Overlay 31)

     The overlay MACLIT contains  the  code  that  generates  literals  and
     controls the literal pool.



     2.9.1  ZSECTG

     The routine ZSECTG obtains a pointer to the program  section  (.ZSECT)
     for  a  Page  0 literal.  It automatically defines a .ZSECT for Page 0
     literals that are referenced from  either  named  or  unnamed  program
     sections.  It performs the following tasks:

	  1.  Takes the pointer to the symbol table entry for  the  program
	      section  of  current  symbol  (CURSCT  (MAC24)),  obtains the
	      program section name, and inserts it into NAME1 through NAME4
	      of the symbol table work area (MAC24).

	  2.  Encodes a leading dollar sign ($) in the name by setting  bit
	      0   of   NAME1   to  a  1.   (The  dollar  sign  signifies  a
	      MACREL-generated .ZSECT.)

	  3.  Passes control to GENUN for further processing if  bit  5  of
	      the  program  section's flag word is 1, indicating an unnamed
	      .ASECT.  (The symbol table contains a MACREL-defined  default
	      name in the form:  FLD:nn.)

	  4.  Searches the symbol table for a program section with  a  name
	      as specified in NAME1 through NAME4 if bit 5 of the flag word

				     2-43
			  DESCRIPTIONS OF THE MODULES


	      is  0  indicating  a  named  program  section.   The  routine
	      proceeds depending on the following situations:

	      a.  If the name is not there, this is the first occurrence of
		  a  Page  0 literal for this program section.  The routine
		  defines a new .ZSECT that resides in the  same  field  as
		  the  program section where the literal reference resides.
		  It uses the original program section name with the dollar
		  sign  appended to it as the name of the new .ZSECT (NAME1
		  through NAME4).  It enters this new program section  name
		  into the symbol table ((QQ)ENTER).

	      b.  If the name is there, it calculates the 15-bit pointer to
		  the  symbol  table entry for the .ZSECT that contains the
		  Page 0 literal, stores it in ZSECTN and exits  with  this
		  value in the AC.



     2.9.2  ZL

     The routine ZL dumps  the  Page  0  literal  pool  for  named  program
     sections.   It  is  an  extension  of  ZLIT and performs the following
     tasks:

	  1.  Exits to the caller if there are currently no page 0 literals
	      for the current program section.

	  2.  Calls ZSECTG to get the program section name,  if  there  are
	      Page 0 literals.

	  3.  (if this is pass 2) Inserts the loader code into  the  binary
	      file (QQ)PUNBIT to instruct LINK to load this program section
	      and sends the literals to the binary file (OUTLIT).

	  4.  (if this is not pass 2) Exits to the caller.



     2.9.3  GENUN

     The routine GENUN generates Page 0 literals for unnamed  .ASECTs.   It
     inserts  these  literals  into  Page  0  of the field where the .ASECT
     resides.  The literals are assigned locations that begin  at  location
     177  and continue in decending address order.  GENUN computes new high
     and low boundaries for this .ASECT, and branches to COMN  (MACEXP)  to
     continue processing.



     2.9.4  ZLIT

     The routine ZLIT purges the Page 0 literal pool.  It branches to  KLU1
     to  see  if  this  pool  is  for an unnamed .ASECT (in which case KLU1

				     2-44
			  DESCRIPTIONS OF THE MODULES


     branches to PRGSPL).  If this pool is for  a  named  program  section,
     ZLIT branches to ZL to purge the pool.  Thereafter, ZLIT clears ZLTLOC
     (MAC24) and ZSECTN (MAC24) to indicate that this Page 0  literal  pool
     is no longer needed.



     2.9.5  PRGSPL

     The routine PRGSPL purges Page 0 literals that reside  in  an  unnamed
     .ASECT.   It  resets  CLTLOC, LPAG, and KIND (to indicate to PLIT that
     the current page literals are to be  purged)  and  branches  to  PLIT.
     Notice  that in an unnamed ASECT, Page 0 literals are in fact the same
     as current page literals if the current page is Page 0.



     2.9.6  KLU10

     KLU10 is a patch to PURGEL that could not fit  on  the  same  page  as
     PURGEL.   It  is  functionally  part  of PURGEL, which is described in
     Section 2.9.7.



     2.9.7  PURGEL

     The routine PURGEL purges literals from a literal pool.  The pool type
     code  resides in the AC upon entry to PURGEL (0 for current page pool,
     1 for Page 0 literal pool).  It performs the following tasks:

	  1.  (if this is a Page 0 literal pool) Branches to ZLIT to  purge
	      the pool.

	  2.  (if this is current page literal pool) Sets LPAG to point  to
	      the  current page literal pool and checks to see if there are
	      any literals in the pool.

	      a.  Exits to the caller if there are no literals in the pool.

	      b.  Calls OUTLIT to  do  the  actual  purging  if  there  are
		  literals  in  the  pool.   (CLTLOC  must be zeroed before
		  OUTLIT is called.)

	  3.  Returns from OUTLIT, and clears CLTLOC and HGHLOC to indicate
	      that this literal pool is unused.



     2.9.8  OUTLIT

     The routine OUTLIT sends a literal pool to  the  binary  file  to  the
     listing  file, or to the KREF file, according to the pass currently in
     effect.  The calling sequence is:

				     2-45
			  DESCRIPTIONS OF THE MODULES


	  TAD (loc
	  JMS OUTLIT
	  pointer

     where:

	  loc	     is the location of the last literal generated in  this
		     pool

	  pointer    is the pointer to  the  literal  table,  either  PAGE0
		     (Page 0 literal table) or CURPAG (current page literal
		     table) (These pointers must begin on a page boundary.)

     It performs the following tasks:

	  1.  (if this is pass 2) Sends the literals via OUTDATA (MAC24) to
	      the binary file.

	  2.  (if this is pass 3) Sends a line of dashes followed by a list
	      of  the  literals  to  the  listing  file.  (The dashed lines
	      separate the literals from the previous code.)

	  3.  (if this is pass 4):

	      a.  Creates a pseudo-name for  each  literal's  location  and
		  value in the form:

		       Lnnnn	= absolute address of the literal

		       Vmmmm	= absolute value of the literal

	      b.  Appends a plus sign  (+)  to  those  literal  names  that
		  represent a value to be relocated by LINK.

	      c.  Sends the names to the KREF file so that the literals can
		  be cross referenced both by name and by value.



     2.9.9  CMNMOV

     The subroutine CMNMOV obtains the next literal value from  either  the
     Current  Page  Literal Table or the Page 0 Literal Table, depending on
     the value of INK.  It returns the value in the AC.

	  INK  =  -1   if purging current page literals
	       =   1   if purging Page 0 literals

	  KIND =   0   if purging current page literals
	       =   1   if purging Page 0 literals





				     2-46
			  DESCRIPTIONS OF THE MODULES


     2.10  MACMAC (Overlays 26, 27, and 30)

     The module MACMAC consists of three overlays that contain the routines
     to implement the macro directives.  Overlay 26 processes the header of
     the macro definition.  Overlay 27 processes  the  body  of  the  macro
     definition and the .REPT directive.  Overlay 30 processes macro calls.



     2.10.1  $MACRO

     The routine $MACRO processes the header of  a  macro  definition.   It
     obtains  the macro name and stores the formal (dummy) arguments in the
     Formal Argument Table (FT).  This  table  contains  groups  of  3-word
     entries.   Each  entry consists of up to 6 characters packed in MACREL
     6-bit code and stored in complemented (negated) form.  A word of zeros
     terminates the table.  Figure 2-2 shows the format of an entry.


			     0		5 6	    11
		       word ---------------------------
			1   |   char 1   |   char 2   |
			    |------------|------------|
			2   |	char 3	 |   char 4   |
			    |------------|------------|
			3   |   char 5   |   char 6   |
			    ---------------------------
					      ML-030 80

		Figure 2-2  Formal Argument Table Entry Format



     2.10.2  PART2

     The routine PART2 stores the macro  body  in  macro  space  and  is  a
     continuation of $MACRO.



     2.10.3  $REPT

     The routine $REPT implements the .REPT  directive.   It  performs  the
     following tasks:

	  1.  Parses the expression that follows the  directive  to  obtain
	      the repeat count and the text of the repeat.

	  2.  Saves the repeat count and text in  macro  storage  space  so
	      that the macro can be repeated.

	  3.  Reacts to the appearance of the .ENDR directive at the end of
	      the repeat range, it:


				     2-47
			  DESCRIPTIONS OF THE MODULES


	      a.  Switches the input stream to RGET (MACIO) to obtain input
		  from macro storage space.

	      b.  Passes control to BYEB  (MAC24)  to  process  the  repeat
		  range.



     2.10.4  MC

     The code MC implements a call to a macro by performing  the  following
     tasks:

	  1.  Reads the actual arguments and stores each  one,  via  STORMS
	      (MACRO),  in  the  argument space (which is the same as macro
	      space).

	  2.  Accepts arguments that are enclosed either in  double  quotes
	      ("text") or in angle brackets (<text>).

	  3.  Accepts an argument that begins with  a  backslash  (\).   In
	      this  case,  it  loads the EXPOVR auxiliary overlay and calls
	      BACKL with a pointer to  STORMS.   This  stores  the  numeric
	      value  of  the  argument  that follows the backslash in macro
	      space according to  the  radix  interpretation  currently  in
	      effect.



     2.10.5  $MEXIT

     The routine $MEXIT implements the .MEXIT directive.  If  MGET  is  not
     the current stream input routine, it returns an error.  If MGET is the
     current input routine, it stores the address of MGT4 (MACIO) in  MRET.
     This causes the macro processor to detect an end to the current string
     in macro space the next time MGET is called.



     2.11  MACOPN (Overlay 33)

     The overlay MACOPN contains routines that open MACREL's output  files.
     This is an extension to the FIN0 overlay.



     2.11.1  OPEN

     The routine OPEN sets up an output file for  either  binary  or  ASCII
     data,  depending  on  the  pass currently in effect.  Whenever OPEN is
     called, it adds the contents of LOCOFF to the starting block number of
     the file to establish the block where output is to begin.  During Pass
     2 LOCOFF contains a value that is the number of blocks in  the  Loader


				     2-48
			  DESCRIPTIONS OF THE MODULES


     Symbol  Dictionary  (LSD) area of the binary file.  This offset allows
     OPEN to skip over the file's LSD area.



     2.11.2  OPENTC

     The routine OPENTC sets up the output file to  receive  the  table  of
     contents.



     2.11.3  OFETCH

     The routine OFETCH loads an output device handler.  There  is  also  a
     copy of this routine in MACIO.



     2.12  MACORG (Overlay 7)

     MACORG is a small module that is an extension of MAC24.   It  contains
     part  of  the  code that controls MACREL's current location counter or
     program counter (PC).  ORIGI, the only entry point in this module,  is
     called from ORPTCH in MAC24.  It performs the following tasks:

	  1.  Sets up LITPAG to the value of the new PC.

	  2.  Zeros EXTPC to indicate that  the  expected  new  PC  is  not
	      external.

	  3.  Passes control to  BYEP  (MAC24)  if  the  new  PC  value  is
	      absolute or is relative to the current program section.

	  4.  Generates an error message in  response  to  the  error  that
	      occurs  if  the  new  PC value is relative to another program
	      section;  attempts to recover from the error by generating an
	      external PC.

	  5.  (if the new PC value is complex relocatable)

	      a.  Generates loader codes that will tell LINK  to  calculate
		  the new PC value at LINK execution time.

	      b.  Sets EXTPC to 1 to indicate that the PC is external.



     2.13  MACRO

     The module MACRO contains Field 0 resident subroutines that  are  used
     by  the macro processor overlays and the Actual (macro) Argument Table
     (AT).  A complete and detailed description of the macro  processor  is
     provided in the comments column of the source listing for this module.

				     2-49
			  DESCRIPTIONS OF THE MODULES


     Table 2-13 contains brief descriptions of the functions of  the  major
     routines.


				  Table 2-13
		    Summary of Routines in the MACRO Module

     ----------------------------------------------------------------------
     |	Routine	    |			Function			  |
     |--------------|-----------------------------------------------------|
     |		    |							  |
     |	CREATE	    | Fetches a new chunk from FREESPACE to be  used  for |
     |		    | macro space.					  |
     |		    |							  |
     |	DELETE	    | Deletes a string of characters from macro space.	  |
     |		    |							  |
     |	DELITE	    | Deletes   the    old    macro    definition    upon |
     |		    | redefinition.					  |
     |		    |							  |
     |	FINMS	    | Terminates storage in macro space.		  |
     |		    |							  |
     |	INITMP	    | Initializes the macro processor  at  the  start  of |
     |		    | each pass.					  |
     |		    |							  |
     |	INITMS	    | Initializes a new chunk for storage.		  |
     |		    |							  |
     |	MATCH	    | Tests a symbol just obtained for  a  match  with  a |
     |		    | given keyword list.				  |
     |		    |							  |
     |	MS	    | Stores a word in  the  current  location  in  macro |
     |		    | space.						  |
     |		    |							  |
     |	RENEW	    | Resets character scan to beginning-of-line.	  |
     |		    |							  |
     |	SKSEP	    | Skips past a sequence of spaces and/or tabs.	  |
     |		    |							  |
     |	STORMS	    | Stores the AC in macro space.			  |
     |		    |							  |
     |	TSTEOL	    | Tests for end-of-line.				  |
     |		    |							  |
     |	TSTQUOTE    | Tests for a double quotation mark (").		  |
     |		    |							  |
     |	TSTTERM	    | Tests for a terminator  (backslash  (\),  semicolon |
     |		    | (;), or end-of-line).				  |
     ----------------------------------------------------------------------


     The Actual (macro) Argument Table (AT) contains 15-bit pointers to the
     argument  strings  (lists)  that  reside in macro storage space.  This
     table is used recursively during the  expansion  of  macro  arguments.
     The  arguments  are  stored  in hierarchical order by nesting level as
     shown in Figure 2-3.



				     2-50
			  DESCRIPTIONS OF THE MODULES


				    --------------------------
		Level 1      arg 1  |   first cell pointer   |
				    |------------------------|
			     arg 1  |	last cell pointer    |
				    |------------------------|
			     arg 2  |	first cell pointer   |
		  .		    |------------------------|
		  .	     arg 2  |	last cell pointer    |
		  .		    |------------------------|
				.   |		.	     |
				.   |		.	     |
				.   |		.	     |
				    |------------------------|
		Level 2	     arg 1  |	first cell pointer   |
				    |------------------------|
		  .	        .   |		.	     |
		  .	        .   |		.	     |
		  .	        .   |		.	     |
				    |------------------------|
		Level n	     arg m  |	last cell pointer    |
				    --------------------------
						     ML-031-80

	       Figure 2-3  Actual (macro) Argument Table Layout



     2.14  MACRTH (Overlay 6)

     The  overlay  MACRTH  is  an  extension  to  the  resident  expression
     processor  MACEXP.   It  contains  the  routines  that request LINK to
     perform global arithmetic for expression constructs that MACREL cannot
     solve.  Table 2-14 describes the function of each routine.


				  Table 2-14
		        Descriptions of MACRTH Routines

     ----------------------------------------------------------------------
     |	Routine	    |			Function			  |
     |--------------|-----------------------------------------------------|
     |		    |							  |
     |	HARDY	    | Obtains   an   expression,   operator,   and   term |
     |		    | combination   from   EXPR  (MACEX)  determines  the |
     |		    | appropriate LINK codes and sends  this  information |
     |		    | to the binary file.				  |
     |		    |							  |
     |	STKPUT	    | Used by HARDY  to  send  the  codes  to  LINK  that |
     |		    | insert a term on its stack.			  |
     ----------------------------------------------------------------------
						 (continued on next page)




				     2-51
			  DESCRIPTIONS OF THE MODULES


			      Table 2-14 (Cont.)
		        Descriptions of MACRTH Routines

     ----------------------------------------------------------------------
     |	Routine	    |			Function			  |
     |--------------|-----------------------------------------------------|
     |		    |							  |
     |	HRDTRM	    | Used by  TERM  (MACEXP)  to  send  the  codes  that |
     |		    | request  LINK to negate a term whose absolute value |
     |		    | cannot be determined by MACREL.			  |
     |		    |							  |
     |	PUT	    | Sends a 12-bit  value  and  associated  flag  field |
     |		    | (value = 3) to the binary file.			  |
     |		    |							  |
     |	FLDYX	    | Processes the .FLD directive in response to a  call |
     |		    | from the $FLD (MACEXP) routine.			  |
     |		    |							  |
     |	XXEDF	    | Processes the XEDF directive in response to a  call |
     |		    | from $XEDF (MACEXP) routine.			  |
     |		    |							  |
     |	CM	    | Clears TRMABS and TRMREL and sets TRMCOD  to  a  -1 |
     |		    | to indicate the  term  is  on  the  top  of  LINK's |
     |		    | stack.						  |
     |		    |							  |
     |	LEVXX	    | Processes the .LEVEL directive  in  response  to  a |
     |		    | call from the $LEVEL (MACEXP) routine.		  |
     ----------------------------------------------------------------------



	2.15  MACTBL

     The module MACTBL is a one-page character branch table.  A  number  of
     routines  in  MAC24  use  this  table  (instead  of calling BRANCH) to
     perform a branch-on-matching character.

     The table consists of 200(octal) entries, one for each ASCII character
     code.  The ordinal position of each entry in the table is the code for
     an ASCII character.  The entries are bit-encoded, as  shown  in  Table
     2-15.   Each  bit specifies an attribute that may be associated with a
     character.  For example, the 101st entry in the table is the entry for
     uppercase  A.   Its  entry  is  0400  (bit  3 set) to specify that the
     character is a letter.



     2.16  MAC2

     The module MAC2 contains the resident code that forms the pass 2  root
     of MACREL.  The following sections describe the major routines.





				     2-52
			  DESCRIPTIONS OF THE MODULES


			          Table 2-15
	     Character Branch Table (MACTBL) Classification Codes

     ----------------------------------------------------------------------
     | Octal | Symbolic | Function	     | Characters Encoded	  |
     |-------|----------|--------------------|----------------------------|
     |	     |		|		     |				  |
     | 4000  | EOL	| End-of-line	     | NUL, FF, LF, CR, CTRL/Z,	  |
     |	     |		|		     |				  |
     | 2000  | EOSY	| End-of-statement   | NUL, ;  and /		  |
     |	     |		|		     |				  |
     | 1000  | BLANK	| Space		     | Space and HT(tab)	  |
     |	     |		|		     |				  |
     | 0400  | LETTER	| Letter	     | A through Z and a through z|
     |	     |		|		     |				  |
     | 0200  | DIGIT	| Digit		     | 0-9			  |
     |	     |		|		     |				  |
     | 0100  | OPER	| Operator	     | HT(tab), space, !, %, &,   |
     |	     |		|		     | +, -, ^			  |
     |	     |		|		     |				  |
     | 0040  | EXTDLT	| Extra Alphanumeric | .  and $			  |
     |	     |		|		     |				  |
     | 0020  | COMMA	| Comma		     | ,			  |
     ----------------------------------------------------------------------



     2.16.1  PUXBIN

     The routine PUXBIN sends a binary entry and  its  flag  field  to  the
     binary  file.   The  flag  field (FLG) must be set up prior to calling
     PUXBIN.  The data word is in the AC.  This routine also increments the
     current  location  counter  (PC)  unless  it is external.  LPATCH is a
     patch that resides in MAC24 and updates the high PC  for  the  current
     program section.



     2.15.2  BPUT

     The routine BPUT stores the current location counter  (PC)  in  LITPAG
     (page  of  current page literals) if the PC overflows into a new page.
     It then calls BPUTX (PAS2) if this is Pass 2 and binary output (PUNCH)
     is enabled.



     2.16.3  PUNBIT

     The routine PUNBIT is identical to PUXBIN except that  it  also  calls
     OUT (MAC3R) to print the current line during pass 3.




				     2-53
			  DESCRIPTIONS OF THE MODULES


     2.16.4  PUTBIT

     The routine PUTBIT sends a binary entry without a flag  field  to  the
     binary file.



     2.16.5  ORIG

     The routine ORIG sets up the flag word (FLG) and sends a  new  current
     location  counter (PC) value to the binary file.  The value of the new
     PC must be in the AC upon entry to this routine.  To account for RELOC
     directives,  the  routine adds the contents of RELOK to the (PC) value
     before calling PUTBIT.



     2.16.6  PUTB

     The routine PUTB calls PUTBT if this  is  pass  2  and  binary  output
     (PUNCH) is enabled.



     2.16.7  PUNY

     The routine PUNY determines whether this is pass 2 and  binary  output
     (PUNCH)  is  enabled.   If these conditions are in effect, it causes a
     "skip-on-condition" by incrementing the return address by 1 so that it
     passes  control  to  the calling address plus 2.  Otherwise, it passes
     control to the calling address plus 1 (standard subroutine return).



     2.16.8  PUTLC

     The routine PUTLC sends a loader code (FLG=3) to the  binary  file  if
     binary output (PUNCH) is enabled and this is pass 2.



     2.16.9  UNNAM

     The routine UNNAM creates a new unnamed .ASECT.  It assigns the .ASECT
     a default name in the form:

	  FLD:nn

     where:

	  nn	 is the field of the .ASECT

     It sets bit 5 of the symbol's flag word in the symbol table entry to 1
     to  specify  that  this  is an unnamed .ASECT (default name assigned).

				     2-54
			  DESCRIPTIONS OF THE MODULES


     Then it tentatively sets the initial  current  location  counter  (PC)
     value to 200.



     2.17  MAC24

     The module MAC24 contains the main body of resident code.  It is often
     referred  to  in the comments to the source code as the "main module".
     MACREL's commonly used variables, flags and constants reside in Page 0
     and extend into Page 1.  The remaining pages contain the routines that
     form the operational core of the assembler.

     The following sections describe the most important routines.



     2.17.1  NEX

     The routine NEX is the start-of-pass code.  Execution  for  each  pass
     begins here.



     2.17.2  GETLSD

     The routine GETLSD obtains the Loader Symbol Dictionary  (LSD)  number
     associated  with  an LSD entry.  Every LSD entry that is to be sent to
     the LSD in the binary (.RB) file is assigned a number.  These  numbers
     are consecutive, beginning at 1.  They are assigned at the end of pass
     1.



     2.17.3  IGNORE

     The routine IGNORE ignores characters in the  current  line  until  it
     finds the end of the line.



     2.17.4  CNVADR

     The routine CNVADR converts an  encoded  15-bit  pointer  into  a  CDF
     instruction and a 12-bit address.  Upon entry into the routine, the AC
     contains the 15-bit  pointer.   Prior  to  returning  to  the  calling
     routine  CNVADR executes a CDF instruction referencing the appropriate
     data field and loads the  12-bit  address  into  the  AC.   (Refer  to
     Section 2.7.5 for the format of 15-bit pointers.)



      2.17.5  $PAUSE


				     2-55
			  DESCRIPTIONS OF THE MODULES


     The routine $PAUSE processes the PAL8 PAUSE directive by ignoring it.



     2.17.6  HGHSCT

     The routine HGHSCT obtains the  highest  address  used  by  a  program
     section.



     2.17.7  LOAD

     The routine LOAD is the overlay  loader.   It  uses  the  OS/8  system
     handler  to  load the specified overlay.  It will not load the overlay
     if it detects that the overlay is already resident.  Thus,  it  checks
     that  the  value  of  bits  7  through 11 of the first location in the
     overlay area is the same as the requested overlay number.  (The  first
     location of an overlay contains the overlay number.)

     The calling sequence is  a  standard  subroutine  call.   The  overlay
     number  (ovrnum) and the first, or lowest, address of the overlay area
     (addr) may be passed to the routine in the location following the call
     (loc),  in  the AC, or in combination as specified below.  If they are
     passed together in the AC, the location following the call (loc)  must
     be zero.  The form is:

	  JMS I (LOAD
	  loc

     where:

	  arg	 = (AC+ loc)	 is the  logical  argument  containing  the
				 data to be passed to the routine

	  ovrnum = (arg + 37)	 is the number of the overlay being  loaded
				 (see Appendix E)

	  addr   = (arg + 7740)  is the first address of the overlay area


				     NOTE

		   MACREL  can  destroy  an  overlay   area
		   without   using   the  formal  mechanism
		   provided by calling LOAD.  For  example,
		   reading  the  input  file  may  make the
		   contents of the EXTREMITIES Overlay Area
		   unusable  if  an  input  handler must be
		   loaded.  Further, it is good practice to
		   zero  the  first location in the overlay
		   area   before   calling   LOAD.     This
		   eliminates  the  no  load condition that
		   could result if the input handler or the

				     2-56
			  DESCRIPTIONS OF THE MODULES


		   data  in the input buffer coincidentally
		   begins with a number that  is  identical
		   to the requested overlay number.



     2.17.8  SETIT

     The routine SETIT creates a new title or  subtitle  from  the  current
     line.  Upon entry, LINPTR contains a pointer to the first character of
     the new title or subtitle.  The calling sequence is:

	  JMS	  I (SETIT
		  -length
		  addr-1

     where:

	 -length     is the complement of the number of characters to move

	 addr-1	     is the address (less 1)  of  the  first  word  of  the
		     destination buffer



     2.17.9  PRZLIT

     The routine PRZLIT uses PURG to load the MACLIT overlay, which  purges
     Page 0 literals.



     2.17.10  PRGLIT

     The routine PRGLIT uses PURG to load the MACLIT overlay, which  purges
     the current page literals.



     2.17.11  BACKSL

     The routine BACKSL calls BACKL (EXPOVR)  to  respond  to  a  backslash
     encountered within a symbol.



     2.17.12  ERROR

     The routine ERROR is the resident part of the error message processor.
     It  accepts  error calls and loads the special overlay MACERR to print
     the error message as follows:

	  1.  Increments the error message counter ERKNT.


				     2-57
			  DESCRIPTIONS OF THE MODULES


	  2.  Saves 5 blocks (12 memory pages) of resident  code  beginning
	      at  memory  location  10400  by storing them in the swap area
	      within MACREL.SV.  The swap area begins at relative block 116
	      (ERRBLK+16),  where  ERRBLK  contains  the  actual OS/8 block
	      number of relative block 100 in SYS:MACREL.SV

	  3.  Reads  blocks  from  ERRBLK+1  of  MACREL.SV   into   memory,
	      beginning at location 11000.  These blocks contain the MACERR
	      code.

	  4.  Branches to routine ERRTN in MACERR to print the error.

	  5.  Passes control to ERROR when MACERR finishes  to  restore  to
	      memory  the  5  blocks that it swapped out.  (It is important
	      that these 5 blocks never contain code that calls ERROR.)

     Refer to Section 2.5.1 for additional information about  ERROR  and  a
     description of MACERR.


				     NOTE

		   Ignore the references  to  MACERR.SV   in
		   the  comments  in  the  listing of ERROR.
		   This is a vestige from the first  release
		   of  MACREL.   The  contents  of MACERR.SV
		   now  reside  in   relative   blocks   101
		   through 116 (octal) of MACREL.SV.



     2.17.13  NEXTCHAR

     The routine NEXTCHAR obtains the next character from the current input
     stream coroutine.



     2.17.14  GETSYM

     The routine GETSYM loads a copy of the symbol table  information  into
     Page  0 for a specified symbol.  The symbol's 15-bit pointer is either
     in the AC or in SYMNUM.  If  the  AC  is  nonzero,  GETSYM  takes  its
     contents  as  a  15-bit  pointer  to  the  desired symbol table chunk.
     Otherwise, it takes the contents of SYMNUM as the pointer.



     2.17.15  PUTSYM

     The routine PUTSYM inserts symbol table information about a  specified
     symbol  into  the symbol table.  The symbol's 15-bit pointer is either
     in the AC or in SYMNUM.  If  the  AC  is  nonzero,  GETSYM  takes  its


				     2-58
			  DESCRIPTIONS OF THE MODULES


     contents as  a 15-bit pointer  to  the  desired  symbol  table  chunk.  
     Otherwise, it takes the contents of SYMNUM as the pointer.



     2.17.16  READLN

     The routine READLN reads a logical line of text from the current input
     stream  coroutine  into  the  input buffer (LINBUF in MACIO).  It uses
     NEXTCHAR to fill the buffer one character at a time.

     READLN  interprets  LF  (line  feed),  CTRL/Z,  and  NUL  as   logical
     end-of-line indicators with the following exceptions:

	  1.  A CTRL/Z also signals the end-of-file.  MACREL requires  that
	      all source files end with a CTRL/Z.

	  2.  An FF (CTRL/L) signifies that a form feed must be sent before
	      printing  the  line.   READLN  sets  the  form flag (FORM) to
	      indicate this.  (The form feed remains in the line.)

	  3.  Vertical TAB is not treated specially.

	  4.  No check is made for a line that is too long.

	  5.  RETURN is ignored.

     READLN signals the end of the logical line by inserting  a  0  in  the
     input line buffer.

     Calling sequence:

	  JMS READLN
	  end-of-file return


				     NOTE

		   Ignore  the  comments   describing   the
		   stream  input routines on page 35 of the
		   assembly listing for  MAC24;   they  are
		   incorrect.



     2.17.17  $FIXMRI

     The routine $FIXMRI implements the FIXMRI directive.   If  the  symbol
     name  argument  to  the  directive  is  a memory reference instruction
     (MRI), it sets bit l in  MRISAV  to  a  1.   In  any  case,  execution
     proceeds into the adjacent direct assignment statement code (EQL).  At
     the end of the EQL routine, it checks bit l of  MRISAV  and,  if  set,
     causes  EQL to set bit l of the symbol's flag word in the symbol table
     entry.

				     2-59
			  DESCRIPTIONS OF THE MODULES


     2.17.18  EQL

     The routine EQL implements the direct assignment statement.  It parses
     the  expression  to  the  right of the equal sign and stores the value
     that results in the value field (word 4) of the symbol table entry  of
     the symbol to the left of the equal sign.



     2.17.19  GETCHR

     The routine GETCHR obtains a character  from  the  input  buffer.   It
     stores the character in CHAR, obtains the type code from the character
     branch table (MACTBL), and places it in BITS.



     2.17.20  SCAN

     The routine SCAN skips over a sequence of spaces and tabs (HT) in  the
     input stream.



     2.17.21  GET

     The routine GET uses GETCHR to retrieve a  character  from  the  input
     buffer and passes control to the caller with the character in the AC.



     2.17.22  CTRLC

     If the routine CTRLC  determines  that  a  CTRL/C  was  typed  at  the
     terminal  keyboard  it aborts the assembly by returning control to the
     OS/8 monitor at location 7605.



     2.17.23  FINI

     The  routine  FINI  loads  Overlay  22  (OVRR)  to  prepare  for   the
     end-of-pass operations and updates the device handler memory residency
     table.



     2.17.24  BACKUP

     The routine BACKUP moves the input buffer pointer  (LINPTR)  back  one
     position,  so  that the next call to GETCHR will return the same value
     that it returned before.



				     2-60
			  DESCRIPTIONS OF THE MODULES


     2.17.25  BRAN

     The routine BRAN implements an indexed branch.  It takes the  contents
     of  the  AC,  adds  it to the return address to create an index into a
     table of addresses, then branches to the selected address.  The  table
     of addresses must immediately follow the call.



     2.17.26  NUMLCL

     The routine NUMLCL processes numeric local labels as follows:

	  1.  Parses a numeric string and evaluates it in decimal radix.

	  2.  Passes control to B2 (MAC24) to process the local symbol if a
	      dollar sign ($) follows the string.

	  3.  Passes control to GETEX2 (MAC24), if there is no dollar  sign
	      after  the  string,  to  reparse  the  numeric  string in the
	      current radix and treat it as an expression.



     2.17.27  BRANCH

     The routine BRANCH implements a branch-on-matching-character function.
     It  searches  a  character/address table for the character or range of
     characters that match the  specified  search  character.   The  search
     character  must be either in the AC or in CHAR (if the AC is 0).  When
     it finds a matching character, it branches to the address in the table
     associated with that character.

     A character/address table must immediately follow the call to  BRANCH.
     Each  entry  consists  of  either  two  or  three  fields delimited by
     semicolons (;).

     If the search object is a single character, the first  field  contains
     the  complement  of  the  character's  6-bit code and the second field
     contains the branch address.

     If the search object is a consecutive ascending range  of  characters,
     the entry consists of three fields.  The first field contains the code
     for the character that begins the range (positive).  The second  field
     is  a  negative  value  that specifies the character range.  The third
     field contains the branch address.


				     NOTE

		   This  routine   is   used   infrequently
		   because   the   calling  sequence  slows
		   MACREL's execution.


				     2-61
			  DESCRIPTIONS OF THE MODULES


     2.17.28  ASEMBL

     ASEMBL is the  controlling  subroutine  that  assembles  a  line.   It
     decides  upon the general format of the line and calls the appropriate
     routine to perform the actual parsing.



     2.17.29  GETEX

     The routine GETEX processes the  asterisk  (*)  directive,  the  right
     angle  bracket  (>) end-of-expression operator, numeric local symbols,
     and lines that contain expressions.



     2.17.30  ASEMLV

     ASEMLV sends the currently assembled statement to the binary file  via
     OUTDATA.   It detects extraneous characters found after the end of the
     current statement and then continues assembly with the next  statement
     on the line.



     2.17.31  OUTDATA

     The routine OUTDATA sends the binary data assembled  by  the  mainline
     code and its 2-bit flag field to the binary file.



     2.17.32  TAGCOM

     The routine TAGCOM processes a tag ending with a comma.



     2.17.33  TAGCOL

     The routine TAGCOL processes a tag that ends with a colon (:), but  it
     does not terminate the current local symbol block.  The 15-bit pointer
     to the symbol table entry for the tag that begins  the  current  local
     symbol block resides in location TAGLOC.



     2.17.34  ORIGIN

     The routine ORIGIN processes the asterisk (*) directive.





				     2-62
			  DESCRIPTIONS OF THE MODULES


     2.17.35  LETTER

     The subroutine LETTER effects a  "skip-on-condition"  if  the  current
     character  (CHAR) is an upper-case or lower-case letter, a period (.),
     or a dollar sign ($).   This  means  that  it  increments  the  return
     address  by 1 so that it passes control to the calling address plus 2.
     Otherwise, it passes control to the calling address plus  1  (standard
     subroutine return).



     2.17.36  TSTMAC

     The routine TSTMAC determines that the first symbol on  a  line  is  a
     macro  call,  it  loads MACMAC (Overlay 30) to expand the macro.  Upon
     completion, it passes control to ASEMLV (via AS3) to assemble the next
     line.  Otherwise, it simply returns control to the caller.



     2.17.37  DIGIT

     DIGIT determines that the current character (CHAR) is a digit,  if  it
     effects a "skip-on-condition" by incrementing the return address by 1.
     It therefore passes control to the calling address plus 2.  Otherwise,
     it  passes  control to the calling address plus 1 (standard subroutine
     return).



     2.17.38  ROTL6

     The subroutine ROTL6 shifts the contents of the AC and  the  link  six
     bits to the left.



     2.17.39  PARSYM

     PARSYM is the symbol  parsing  routine.   It  performs  the  following
     tasks:

	  1.  Parses an identifier from the line beginning with the current
	      character.

	  2.  Converts the identifier's  characters  from  6-bit  ASCII  to
	      MACREL 6-bit representation (see Appendix A).

	  3.  Inserts the first six characters of the identifier into NAME1
	      through  NAME3 of the symbol table work area and discards any
	      extra characters.

	  4.  Sets the QUAL word to 0 if the symbol does  not  end  with  a
	      dollar sign ($).

				     2-63
			  DESCRIPTIONS OF THE MODULES


	  5.  Sets QUAL to the value  of  TAGLOC  (15-bit  pointer  to  the
	      current  local  symbol block) if the symbol is a local symbol
	      and ends with a dollar sign ($).

	  6.  Assumes that it is going to parse a file name if  the  AC  is
	      nonzero  on  entry  to PARSYM.  It inserts the file name into
	      NAME1 through NAME3 and the extension in NAME4 of the  symbol
	      table  work  area  (MAC24).  It ignores any characters in the
	      file name and the  extension  that  exceed  the  limits  (six
	      characters for file names and two for extensions).



     2.17.40  EOS

     The routine EOS determines whether the current character (BITS)  is  a
     statement  delimiter.  It checks for forward slash (/), semicolon (;),
     and end-of-line (NUL, LF, FF, RETURN and CTRL/Z)  characters.   If  it
     does    not   find   one   of   these   characters,   it   effects   a
     "skip-on-condition" by incrementing the return address by 1 so that it
     passes  control  to  the calling address plus 2.  Otherwise, it passes
     control to the calling address plus 1 (standard subroutine return).



     2.17.41  LOOP

     The routine LOOP forms the main control loop  of  the  assembler.   It
     calls  READLN,  and  ASEMBL  repetitively  to read and assemble source
     lines until it encounters the end of the input file,  It  calls  CTRLC
     to  determine  if  the  user  typed  a CTRL/C at the terminal to abort
     MACREL operation.



     2.17.42  CALLIT

     The routine CALLIT allows routines that reside in  fields  other  than
     Field 0 to call routines that reside in Field 0.  The calling sequence
     is:

	  CDF
	  CIF 0
	  TAD (arg
	  JMS CALLIT
	  address
	  return 1
	  return 2
	  return 3

     where:

	  arg	      is the argument to be passed in AC


				     2-64
			  DESCRIPTIONS OF THE MODULES


	  address     is the field 0 address of the routine to be called

     This routine has from  one  to  three  returns  immediately  following
     address   argument,  depending  on  the  conventions  of  the  routine
     beginning at address.



     2.17.43  GETKAR

     The routine GETKAR retrieves a character from the  input  buffer.   It
     returns  to  the  caller with the character in the AC.  If this is the
     end-of-line (AC=0), it increments the return  address  by  1  so  that
     control  passes  to  the calling address plus 2.  Otherwise, it passes
     control to the calling address plus 1 (standard subroutine return).



     2.17.44  PUSH

     The routine PUSH places  (pushes)  the  contents  of  the  AC  on  the
     expression stack (EXPSTK in MACIO).



     2.17.45  POP

     The routine POP removes (pops) a value from the expression  stack  and
     leaves it in the AC.



     2.17.46  LOOKUP

     The routine LOOKUP searches the symbol table for the name contained in
     NAME1 through NAME3 of the symbol table work area (MAC24).  If it does
     not find the name, control passes to the calling address plus 1 (ready
     to  call  ENTER).   If it does find the name, it passes control to the
     calling address plus 2 with auto-index register XR0 set  to  point  to
     word  3  (SYMVAL) of the symbol table entry with the data field set to
     Field 0.



     2.17.47  CREF

     The routine CREF sends the symbol name and line number information  to
     the  cross-reference  (KREF)  file.  The name resides in NAME1 through
     NAME3 of the symbol table work area, and the line  number  resides  in
     LINENO and LINEN2.





				     2-65
			  DESCRIPTIONS OF THE MODULES


     2.17.48  ENTER

     The routine ENTER enters the symbol name that resides in NAME1 through
     NAME3  of  the symbol table work area into the symbol table.  ENTER is
     ordinarily called after a symbol table search (LOOKUP) fails.



     2.17.49  KLU4

     The routine KLU4 obtains the lowest address  used  by  an  .ASECT  and
     stores it in HGHTMP.



     2.18  MAC30 (Overlay 15)

     The overlay MAC30 contains the pass 1 and pass 3 specific code.



     2.18.1  PRINTY

     The routine PRINTY sends the  current  location  counter  (PC)  value,
     binary data, and symbol qualifiers that are printed at the left of the
     assembly listing  to  the  print  routine  ((QQ)LISTER).   The  symbol
     qualifiers are defined in Table 2-16.



     2.18.2  PRLINO (MAC2)

     The routine PRLINO prints the line number at the left  margin  of  the
     assembly listing.


				  Table 2-16
		    Assembly Listing Symbol Name Qualifiers

		  --------------------------------------------
		  |      Qualifier	 |	Meaning	     |
		  |----------------------|-------------------|
		  |			 |		     |
     		  |  ' (apostrophe)	 | Link generated    |
		  |			 |		     |
     		  |  blank		 | Type 0 relocation |
		  |			 |		     |
     		  |  +			 | Type 1 relocation |
		  |			 |		     |
     		  |  -			 | Type 2 relocation |
		  |			 |		     |
     		  |  *			 | Type 3 relocation |
     		  --------------------------------------------


				     2-66
			  DESCRIPTIONS OF THE MODULES


     2.18.3  SETT

     The routine SETT sets a new title from the  current  line  by  calling
     SETIT with the appropriate parameters.



     2.18.4  DPRINT

     The routine  DPRINT  sends  the  decimal  number  in  the  AC  to  the
     number-printing routine NPRINT.



     2.18.5  OPRINT

     The  routine  OPRINT  sends  the  octal  number  in  the  AC  to   the
     number-printing routine NPRINT.



     2.18.6  NPRINT

     The routine NPRINT sends the number obtained from  DPRINT  and  OPRINT
     to  the  actual print routine ((QQ)LISTER).  It performs the following
     tasks:

	  1.  Examines  the  link  bit  to  determine  how  to  pad  unused
	      character positions in the number being printed.

	  2.  Pads the number (4 places) with leading zeros if the link  is
	      set.

	  3.  Pads the number with the character contained in  PAD  if  the
	      link is not set.

	      Examples:

	      a.  If PAD contains a space character, the number is  printed
		  with leading spaces.

	      b.  If PAD contains a zero, the number  is  printed  with  no
		  leading spaces.



     2.18.7  CRLF

     The routine CRLF  sends  a  RETURN/LF  sequence  to  ((QQ)LISTER)  for
     printing.





				     2-67
			  DESCRIPTIONS OF THE MODULES


     2.18.8  LIST

     The  routine  LIST  prints  an  entire  line  (or  sequence  of  ASCII
     characters).  The calling sequence is:

	  JMS LIST
	  pointer to ASCII line

     The ASCII line must reside in Field 1.  The  line  consists  of  ASCII
     characters  (one  character  per word, terminated by a word of zeros).
     If the AC is zero on entry to the routine, the  routine  automatically
     prints a RETURN/LF sequence after the string of characters.  If the AC
     is nonzero on entry, the routine terminates operation and  returns  to
     the caller without sending the RETURN/LF sequence.



     2.18.9  PRNDSH

     The routine PRNDSH sends five dashes to ((QQ)LISTER  to  the  listing.
     They separate the assembled code from the literals that are printed at
     the end of each memory page of assembly listing.



     2.18.10  PRNBIN

     The routine PRNBIN sends the  assembled  code  (octal)  to  the  print
     routine  ((QQ)LISTER)  for  printing at the left of its source line in
     the listing.  If FLG is negative, the current  expression  is  complex
     relocatable,  and  it  sends  four  asterisks  (****)  instead  of the
     assembled value.



     2.18.11  TAB

     The routine TAB sends an HT (horizontal tab) character to the  listing
     file and increments the tab stop count (COLCNT).



     2.19  MAC3R

     This module contains the resident portion of the Pass  1  and  Pass  3
     specific code.



     2.19.1  OUT

     The routine OUT sends a line to the listing  file.   It  performs  the
     following tasks:


				     2-68
			  DESCRIPTIONS OF THE MODULES


	  1.  Calls NEWPAG to start a new listing page  if  the  form  flag
	      (FORM) is nonzero.

	  2.  Returns control to the caller if this is not pass  3,  or  if
	      the listing flag is off.

	  3.  Returns control to the caller if there is no  line  to  print
	      and the binary extension flag (BNFLAG) is not set.



     2.19.2  NEWPAG

     The routine NEWPAG sets up  a  new  listing  page  for  printing.   It
     accepts  an  optional  argument  in  the  AC that specifies a sub-page
     number.  If the AC is zero, there is no sub-page number.  If the AC is
     nonzero, it takes this value as the new sub-page number to be printed.
     (The sub-page number is incremented whenever a logical memory page  of
     code crosses a physical page boundary.)

     NEWPAG performs the following tasks:

	  1.  Returns to the caller immediately if this is not pass 3.


				     NOTE

		   Whether or not it is pass  3,  OUT  must
		   perform  a  minimal amount of processing
		   to  maintain  line   and   page   number
		   accuracy.       For     example,     the
		   cross-reference (KREF) pass requires the
		   line  number  count, and pass 1 uses the
		   page  number   count   to   create   the
		   table-of-contents.


	  2.  Checks NEWTIT to see if a new title was specified.  If NEWTIT
	      is  nonzero,  NEWPAG  obtains  the  new title line by calling
	      SETT, which moves a new title into the heading area from  the
	      beginning of the current source line.

	  3.  Prints:

	      a.  the heading (TITLE), starting with an FF (form  feed)  as
		  the first character

	      b.  the page number with no leading zeros

	      c.  a hyphen (-) followed by the sub-page number (if this  is
		  not sub-page 0)

	      4.  Sets the form feed flag (FORM) to 0.


				     2-69
			  DESCRIPTIONS OF THE MODULES


	      5.  Prints a RETURN/LF sequence followed by the subtitle  and
		  another RETURN/LF.

	      6.  Resets the line count to the negated value of PGLINS  and
		  returns to the caller.



     2.19.3  LISTER

     LISTER is the primary routine for printing characters during passes  1
     and  3.   This  routine  calls LISTOR (MACIO) in Field 1.  The calling
     sequence is:

	  TAD (char
	  JMS I [LISTER

     or

	  TAD (char
	  JMS QQLISTER



     2.19.4  OVRLIN

     The routine OVRLIN allows lines in the  listing  to  continue  onto  a
     continuation page.  It performs the following tasks:

	  1.  Resets the column count (COLCNT) to the standard  page  width
	      (-WIDTH).

	  2.  Increments the line count (LINCNT).

	  3.  Increments the sub-page number (SUBPAG) if this is the end of
	      the  page;   calls NEWPAG to create a new page;  and sets the
	      line count (LINCNT) to 1.



     2.19.5  PASS3

     If the routine PASS3 determines that a pass is pass 3,  it  effects  a
     "skip-on-condition"  by  incrementing  the  return  address  by 1.  It
     therefore passes control to the calling address plus 2.  Otherwise, it
     passes  control  to  the  calling  address plus 1 (standard subroutine
     return).



     2.20  OVRA (Overlay 1)

     The overlay OVRA  contains  the  routines  that  implement  the  PAGE,
     ZBLOCK, and TEXT directives.

				     2-70
			  DESCRIPTIONS OF THE MODULES


     2.20.1  $PAGE

     The routine $PAGE implements the PAGE directive.  Since it can  change
     the  value  of  the current location counter (PC), it uses the current
     value of the PC when calling HGHSCT to compute the  current  high  PC.
     (This  allows  for  the  rare  case  when  a PAGE directive resets the
     current location counter to a value that is  lower  than  the  current
     PC.)  If  an  argument  follows,  the  keyword,  $PAGE parses it as an
     expression that specifies a new page number.  This must be an absolute
     expression  in the range 0-37.  If there is no argument, $PAGE assumes
     that it is the next page.

     $PAGE sets up the new PC and if different from the page of the current
     page  literals (LITPAG), it calls PRGLIT to purge the previous current
     page literals.  Paging to the  current  page,  though  of  no  logical
     value,  will  not  cause the literal pool to be purged.  Then it calls
     ORIG to set up the new PC.



     2.20.2  $ZBLOCK

     The routine $ZBLOCK implements the ZBLOCK directive.  It performs  the
     following tasks:

	  1.  Parses the first expression that  follows  the  directive  to
	      find  the  length  of  the  block.   A  length of zero causes
	      control to return to PSEUDB (MAC24) and ignore the directive.
	      Otherwise, it temporarily stops printing binary extensions in
	      order not to list multiple duplicate binary values.

	  2.  Parses the optional second expression if it  finds  a  comma.
	      This is the value to be inserted into each word in the block.
	      If there was no comma, the default value is zero.  It  calls
	      PUNBIT repetitively to send out this value.



     2.20.3  $TEXT

     The routine $TEXT implements the  TEXT  directive.   It  performs  the
     following tasks:

	  1.  Interrogates  ENABWD  to  determine  what  character  packing
	      options the user specified.

	  2.  Parses the characters that remain in the source line.

	  3.  Calls one of the coroutines listed in Table 2-17 to pack each
	      character  that  it  finds  (if necessary) and send it to the
	      binary output file.

	  4.  Sends NULs to the  appropriate  coroutines  to  complete  the


				     2-71
			  DESCRIPTIONS OF THE MODULES


	      operation and to guarantee that the text string is terminated
	      by a full word of zeros.

	  5.  Sends one additional NUL if the user specified zero fill.


				  Table 2-17
			   TEXT Directive Coroutines

     ----------------------------------------------------------------------
     |	Name   |NULs| 		       Description			  |
     |---------|----|-----------------------------------------------------|
     |	       |    |							  |
     |  ASCTXT |  0 | Packs text in 8-bit ASCII format (1  character  per |
     |         |    | word).						  |
     |	       |    |							  |
     |  SIXTXT |  1 | Packs text in 6-bit ASCII format (2 characters  per |
     |         |    | word).						  |
     |	       |    |							  |
     |  OS8TXT |  2 | Packs text in  OS/8  format  (3  characters  per  2 |
     |         |    | words).						  |
     |	       |    |							  |
     |	USRTXT |  1 | User-defined text routine. This currently generates |
     |         |    | two  6-bit  characters  per  word  according to the |
     |         |    | "excess 237" encoding scheme.  Refer to the COS-310 |								  _______
     |         |    | User's Manual.					  |		      _____________
     ----------------------------------------------------------------------


				     NOTE

     		    The USRTXT entry point  allows  you  to
     		    define    and    implement   your   own
     		    text-packing scheme within MACREL.   To
     		    do  this,  merely  patch  the  location
     		    USRTXT to contain a JMP to your special
     		    text-packing coroutine.



     2.21  OVRB (Overlay 2)

     The overlay OVRB contains the routines that implement the  conditional
     assembly directives:  IFNZRO, IFZERO, IFDEF, IFNDEF, and .IF.



     2.21.1  $IFNZRO

     The routine $IFNZRO implements the IFNZRO directive.  It uses the same
     code as the .IF NE directive (see Section 2.21.5).




				     2-72
			  DESCRIPTIONS OF THE MODULES


     2.21.2  $IFZERO

     The routine $IFZERO implements the IFZERO directive.  It uses the same
     code as the .IF EQ directive (see Section 2.21.5).



     2.21.3  $IFDEF

     The routine $IFDEF implements the IFDEF directive.  It uses  the  same
     code as the .IF DF directive (see Section 2.21.5).



     2.21.4  $IFNDEF

     The routine $IFNDEF implements the IFNDEF directive.  It uses the same
     code as the .IF ND directive (see Section 2.21.5).



     2.21.5  $IF

     The routine  $IF  implements  the  .IF  directive.   It  performs  the
     following tasks:

	  1.  Examines the condition keyword  that  follows  the  directive
	      keyword  and  branches  to  the  routine associated with that
	      keyword to determine if the condition is true or  false  (see
	      Table 2-18).

	  2.  Passes control to CONDOK if the condition is true.  CONDOK:

	      a.  Scans to the right angle bracket (>).

	      b.  Increments CONCNT to maintain a count of the  conditional
		  nesting level.

	  3.  Passes control to SKIP if the condition is false.  SKIP:

	      a.  Skips the range of the conditional by  scanning  for  the
	      right angle bracket (>) that terminates the condition.

	      b.  Prints the lines of source code in  the  condition  range
		  unless /J option was selected.

	      It uses ANGCNT to count the levels of inner nesting of  angle
	      brackets.







				     2-73
			  DESCRIPTIONS OF THE MODULES


				  Table 2-18
			   .IF Directive Conditions

		  -------------------------------------------
		  | Argument *  |    Condition When True    |
		  |-------------|---------------------------|
		  |		|			    |
		  |   EQ	| expression=0		    |
		  |		|			    |
		  |   NE	| expression not equal 0    |
		  |		|			    |
		  |   LT	| expression < 0	    |
		  |		|			    |
		  |   GE	| expression >= 0	    |
		  |		|			    |
		  |   GT	| expression > 0	    |
		  |		|			    |
		  |   LE	| expression <= 0	    |
		  |		|			    |
		  |   DF	| symbol defined	    |
		  |		|			    |
		  |   NDf	| symbol not defined	    |
		  |		|			    |
		  |   B		| string empty (blank)	    |
		  |		|			    |
		  |   NB	| string non-empty	    |
		  |		|			    |
		  |   IDn	| pair of strings identical |
		  |		|			    |
		  |   DIf	| pair of strings different |
		  |		|			    |
		  |   REf	| symbol referenced	    |
		  |		|			    |
		  |   NRef	| symbol not referenced	    |
		  |		|			    |
		  |   ABs	| expression absolute	    |
		  |		|			    |
		  |   REl	| expression relocatable    |
		  -------------------------------------------
	        * Lowercase characters in keywords are optional.



     2.22  OVRC (Overlay 3)

     The  overlay  OVRC  implements  the  .TASK,  OCTAL,  DECIMAL,  .RADIX,
     FILENAME, DEVICE, and .ENABLE directives.



     2.22.1  TASKY

     The routine TASKY implements  the  obsolete  .TASK  directive  and  is


				     2-74
			  DESCRIPTIONS OF THE MODULES


     included as comments for historical purposes.  The directive no longer
     appears in the permanent symbol table.



     2.22.2  $OCTAL

     The routine $OCTAL implements the OCTAL directive.  It sets the  radix
     to  8  instead  of  10 and continues into the code that implements the
     DECIMAL directive.



     2.22.3  $DECIMA

     The routine $DECIMA implements the DECIMAL  directive.   It  sets  the
     radix to 10 (decimal).



     2.22.4  $RADIX

     The routine $RADIX implements the .RADIX  directive.   It  temporarily
     sets  the  radix  (RADXWD)  to  decimal  (default),  then  parses  the
     expression that follows.  If the value of  the  expression  is  0,  1,
     negative,  greater  than  10, or nonabsolute, then an error message is
     generated.  Otherwise, it accepts the value of the expression  as  the
     new radix.



     2.22.5  $FILENA

     The routine $FILENA implements the FILENAME  directive.   It  performs
     the following tasks:

	  1.  Scans past leading spaces, then calls PARSYM with a 1 in  the
	      AC.  (The 1 sets PARSYM to scan for file names by rejecting a
	      symbol that contains a dollar sign and by accepting a  symbol
	      that contains the period that signals a file name extension.)
	      PARSYM sets up the name in NAME1 through NAME 4 of the symbol
	      table work area.

	  2.  Calls PUNBIT, which generates the  binary  code  if  this  is
	      logical pass 2.

	  3.  Calls PSEUDB, which sends it to the listing file if  this  is
	      logical pass 3.







				     2-75
			  DESCRIPTIONS OF THE MODULES


     2.22.6  $DEVICE

     The routine $DEVICE implements the DEVICE directive  and  shares  code
     with the $FILENAME routine.  It performs the following tasks:

	  1.  Scans past leading spaces, then calls PARSYM with a 1 in  the
	      AC.  (The 1 sets PARSYM to scan for file names by rejecting a
	      symbol that contains a dollar sign and by accepting a  symbol
	      that contains the period that signals a file name extension.)
	      PARSYM sets up the name in NAME1 through NAME 4 of the symbol
	      table work area.

	  2.  Checks NAME3 and NAME4, when control returns from PARSYM,  to
	      determine  that  there  were not more than four characters in
	      the device name and that there were no periods.  If  this  is
	      not true, it generates an error message.

	  3.  Calls PUNBIT, which generates the  binary  code  if  this  is
	      logical pass 2.

	  4.  Calls PSEUDB, which sends it to the listing file if  this  is
	      logical pass 3.



     2.22.7  $ENABLE

     The routine $ENABLE implements the .ENABLE directive.   It  begins  by
     parsing  the  symbol that represents the enable condition keyword.  It
     then passes control to one of the routines listed in Table 2-19 to set
     the  correct  bits  in  the  ENABWD  variable.   Only  the  first  two
     characters of the keyword are significant.  (Refer to the  MACREL/LINK								___________
     User's Manual for the bit significance of .ENABWD.)     _____________


				  Table 2-19
			   $ENABLE Condition Options

			-------------------------------
			| Keyword*	    | Routine |
     			|-------------------|---------|
			|		    |	      |
			| 7Bit		    |  BIT7   |
			|		    |	      |
			| 8Bit		    |  BIT8   |
			|		    |	      |
			| AScii		    |  ASCII  |
			|		    |	      |
			| COs		    |  COS    |
			|		    |	      |
			| EXpunge	    |  EXPUN  |
			-------------------------------
			     (Continued on next page)


				     2-76
			  DESCRIPTIONS OF THE MODULES


			      Table 2-19 (Cont.)
			   $ENABLE Condition Options

			-------------------------------
			| Keyword*	    | Routine |
     			|-------------------|---------|
			|		    |	      |
			| FIll		    |  FILL   |
			|		    |	      |
			| NO**		    |  NO     |
			|		    |	      |
			| OR		    |  ORR    |
			|		    |	      |
			| OS8		    |  OS8    |
			|		    |	      |
			| PEerm		    |  PERMY  |
			|		    |	      |
			| PUnch		    |  PUNCH  |
			|		    |	      |
			| SHift		    |  SHIFT  |
			|		    |	      |
			| SIxbit	    |  SIXBIT |
			-------------------------------

	* Lowercase characters in keywords are optional.

	** The NO  routine  takes  the  remainder  of  the  keyword  (in
	NAME2)and branches into the routine that implements the .DISABLE
	directive.  The NOFILL, NOEXPUNGE,  NOPERM,  NOLSB  and  NOPUNCH
	conditions  behave  this  way.   For  example, .ENABLE NOFILL is
	treated as .DISABLE FILL.



     2.22.8  $DISABL

     The routine $DISABL implements the .DISABLE directive.  It  begins  by
     parsing  the symbol that represents the disable condition keyword.  It
     then passes control to one of the routines listed in Table 2-20 to set
     the  correct  bits in the ENABWD variable (MAC24).  Only the first two
     characters of the keyword are significant.  (Refer to the  MACREL/LINK								___________
     User's Manual for the bit significance of .ENABWD.)     _____________


     2.23  OVRD (Overlays 4 and 35)

     The module OVRD consists of two overlays.  Overlay  4  implements  the
     .SECT  directive  and all its variants.  Overlay 35 is an extension to
     Overlay 4 that processes the overlay control arguments  to  the  .SECT
     directive.

     Table 2-21 shows the entry points in Overlay 4 and the current program
     section type (CST) values associated with each.


				     2-77
			  DESCRIPTIONS OF THE MODULES


				  Table 2-20
			   $DISABL Condition Options

			  ---------------------------
			  | Keyword	  | Routine |
			  |---------------|---------|
			  |		  |	    |
			  | FIll	  | NOFILL  |
			  |		  |	    |
			  | EXpunge	  | NEXPUN  |
			  |		  |	    |
			  | PErm	  | NOPERM  |
			  |		  |	    |
			  | PUnch	  | NOPUN   |
			  |		  |	    |
			  | LS		  | NOLSB   |
			  ---------------------------


				  Table 2-21
		       OVRD Entry Points and CST Values

			 ------------------------------
			 | Entry Point    | CST Value |
			 |----------------|-----------|
			 |		  |	      |
			 | $XSECT	  |     10    |
			 |		  |	      |
			 | $ZSECT	  |     20    |
			 |		  |	      |
			 | $DSECT	  |     30    |
			 |		  |	      |
			 | $FSECT	  |     40    |
			 |		  |	      |
			 | $RSECT	  |     50    |
			 |		  |	      |
			 | $ASECT	  |     60    |
			 ------------------------------


     Overlay 4 performs the following tasks:

	  1.  Sets up CST, depending on the  entry  point  ($XSECT  through
	      $ASECT),  to contain the value of the current program section
	      type.  In the case of an  entry  via  $SECT,  it  parses  the
	      argument that specifies the directive type to set up CST.

	  2.  Stores the 15-bit pointer to the previous program section  in
	      PRVSCT in case a .SECT* directive had been specified.

	  3.  Stores the 15-bit pointer to the current program  section  in
	      OLDSCT.



				     2-78
			  DESCRIPTIONS OF THE MODULES


	  4.  Computes a new high current location counter (PC) for the old
	      program section.

	  5.  Purges all literal pools  and  cancels  any  RELOC  directive
	      currently in effect.

	  6.  Obtains the new program section name  and  sends  it  to  the
	      cross-reference (KREF) file.

	  7.  Searches the symbol table for the name of the program section
	      to  obtain  more information about the symbol.  If the symbol
	      is not defined, it defines the symbol.

	  8.  Starts a new local symbol block (LSB) by clearing TAGLOC.

	  9.  Initializes itself to  continue  loading  into  this  program
	      section.

	 10.  Loads Overlay 35, if the argument list continues, to  process
	      the  PAGE, LOCATION, CONCATENATE, OVERLAY, LEVEL, NOPURGE and
	      ROOT overlay control keywords.  If Overlay 35  finds  any  of
	      these  keywords,  it  parses  the expression that follows and
	      inserts  the  information  into  locations  in  the   program
	      section's symbol table entry.



     2.24  OVRE (Overlay 5)

     The overlay OVRE implements the .CHAIN, .INCLUDE,  .ENTRY,  .EXTERNAL,
     .ZTERNAL, .GLOBAL, and .SECREF directives.



     2.24.1  $CHAIN

     The routine $CHAIN implements the .CHAIN directive.  It sets CHNFLG to
     1  and proceeds with the routine that processes the .INCLUDE directive
     (which sets CHNFLG to 0).



     2.24.2  $INCLUD

     The routine $INCLUD implements the .INCLUDE  directive.   It  performs
     the following tasks:

	  1.  Parses the device and file name.

	  2.  Fetches the handler, then calls CHAINI (MACIO in Field 1)  to
	      complete the task.

	  3.  Sets up:


				     2-79
			  DESCRIPTIONS OF THE MODULES


	      a.  the new input device handler entry point

	      b.  the new input record number

	      c.  the new input file length (INLEN)

	  4.  Returns through BYEB to the  ASEMLV  routine  (MAC24),  which
	      begins parsing the new input file.



     2.24.3  $ENTRY

     The routine $ENTRY computes the global type code (4)  for  the  .ENTRY
     directive  by performing address arithmetic and deposits it in GLBTYP.
     Execution then proceeds with the  general  global  processing  routine
     GLOB2 (described in Section 2.24.7).



     2.24.4  $EXTERN

     The routine  $EXTERN  computes  the  global  type  code  (6)  for  the
     .EXTERNAL  directive  by performing address arithmetic and deposits it
     in GLBTYP.  Execution then proceeds with the general global processing
     routine GLOB2 (described in Section 2.24.7).



     2.24.5  $ZTRNA

     The routine $ZTRNA computes the global type code (7) for the  .ZTERNAL
     directive  by performing address arithmetic and deposits it in GLBTYP.
     Execution then proceeds with the  general  global  processing  routine
     GLOB2 (described in Section 2.24.7).



     2.24.6  $GLOBAL

     The routine $GLOBAL deposits the global type code (5) for the  .GLOBAL
     directive and deposits it in GLBTYP.  Execution then proceeds with the
     general global processing routine GLOB2 (described in Section 2.24.7).



     2.24.7  GLOB2

     The GLOB2  is the  general  global  processing  routine  for  all  the
     directives  contained in this overlay.  Execution control passes to it
     from the $ENTRY, $EXTERNAL, $ZTERNAL, $GLOBAL,  and  $SECREF  routines
     once GLBTYP is set to the global type code.  It performs the following
     tasks:


				     2-80
			  DESCRIPTIONS OF THE MODULES


	  1.  Parses a sequence of identifiers separated by commas.

	  2.  Performs a symbol table  look-up  for  each  identifier,  and
	      enters  in  the  symbol  table  those identifiers not already
	      entered.

	  3.  Enters each identifier in the cross-reference (KREF)  listing
	      file.

	  4.  Sets the appropriate bit in the symbol table's flag word.



     2.25  OVRQ (Overlays 21 and 34)

     The module OVRQ consists of two overlays.   Overlay  21  contains  the
     block letter printing routines.  Overlay 34 contains the routines that
     print the macrel fish caricature, the version code, and the number  of
     errors.   Both  of  these  overlays  are  a  logical part of the OPEN3
     routine in the FIN0 overlay.



     2.25.1  BLKLET

     The routine BLKLET sets up the block letter printer (OUTBLK) to  print
     the  block  letters  header  on the assembly listing.  It performs the
     following tasks:

	  1.  Stores the contents of the AC  (width  of  the  basic  letter
	      block) in GROUP.

	  2.  Sets up the word pointer (BLKPTR) to point to the first  word
	      of the listing file name.

	  3.  Calls OUTBLK twice:  once with an argument of -3 to print the
	      3 words (6 characters) of block letters of the  listing  file
	      name  and  once  with  an argument of -1 to print the 2 block
	      letters of the listing file name extension.



     2.25.2  OUTBLK

     The routine OUTBLK converts a sequence  of  6-bit  characters  into  a
     sequence  of block letters and prints them on the listing device.  For
     each 6-bit character, it finds a matching entry  in  one  of  two  bit
     tables  that contain the coordinates of the associated block letter or
     digit.  Before OUTBLK is called:

	  1.  GROUP must contain the number of characters (negative  value)
	      that  comprise  the  width  of the basic letter block for the
	      heading being printed (see Section 2.2.4).


				     2-81
			  DESCRIPTIONS OF THE MODULES


	  2.  BLKPTR must point  to  the  first  word  of  the  name  being
	      printed.  The name consists of a group of words containing
	      characters that are packed in 6-bit ASCII.


     OUTBLK's calling sequence is:

	  JMS OUTBLK
	  nchars

     where:

	  nchars     is the two's complement of the number of characters to
     		     print



     2.25.3  BINFO

     The routine BINFO prints  on  the  listing  header,  the  macrel  fish
     caricature,  MACREL's  version code, and the number of assembly errors
     found during assembly.  If there were no errors, it prints  a  smiling
     fish.  Otherwise, it prints a scowling fish.



     2.26  OVRR (Overlay 22)

     The overlay OVRR contains  the  routines  that  implement  the  XLIST,
     NOPUNCH,   ENPUNCH,   .JSW,   .VERSION,  .START,  .LIST,  and  .NOLIST
     directives.



     2.26.1  $XLIST

     The routine $XLIST implements the XLIST directive by complementing bit
     0 in LISTWD.



     2.26.2  PREFIN

     The routine PREFIN is called by FINI (MAC24) at the end of  each  pass
     prior  to  loading  the  FIN  overlays.   It  performs  the  following
     initialization tasks:

	  1.  Marks the FIN overlay area as being empty.

	  2.  Sets up the device handlers for the correct pass.

	  3.  Purges the literal pools that remain.



				     2-82
			  DESCRIPTIONS OF THE MODULES


	  4.  Loads Overlay 12 if this is pass  1,2  or  4.   Otherwise  it
	      loads Overlay 13.



     2.26.3  $NOPUNC

     The routine $NOPUNC implements the NOPUNCH directive by setting PUNFLG
     to 1.



     2.26.4  $ENPUNC

     The routine $ENPUNC implements the ENPUNCH directive by setting PUNFLG
     to 0.



     2.26.5  $JSW, $VERSIO, and $START

     The three labels $JSW, $VERSIO, and  $START  are  entry  points  to  a
     single   routine  that  implements  the  .JSW,  .VERSION,  and  .START
     directives.  It performs the following tasks:

	  1.  Sets LOC to point to START, START+l, or START+2, depending on
	      the directive.  These are once-only-code locations  in  MAC24
	      that  are  zeroed.   (The  contents of LOC added to 4, is the
	      address of the word that is zeroed.) This indicates which  of
	      the three directives was specified.

	  2.  Parses the expression that is the argument to each  directive
	      and stores it in the proper constant location.

	  3.  Checks for a starting field and a starting address if this is
	      a  .START  directive.   (The  address may be relocatable.) It
	      stores the relocatable portion of  the  starting  address  in
	      STARTR.   The  field number must be less than 10 (octal).  It
	      also is stored in STARTR because being less than 10 makes  it
	      distinguishable from a 15-bit pointer.



     2.26.6  $NOLIST and $LIST

     The two labels $NOLIST and $LIST are entry points to a single  routine
     that   implements   the   .NOLIST  and  .LIST  directives.   The  only
     operational difference in processing the directives  is  that  $NOLIST
     sets LSTCOD to 4000 while $LIST sets LSTCOD to 0.  Since setting a bit
     to 1 means no condition (NO) in LISTWD, LSTCOD  is  used  to  force  a
     specific  bit  to 1 or to 0 in the LISTWD variable.  The routine scans
     the  argument  list  for  the  allowable  conditions  and   sets   the
     appropriate  location  in  LISTWD.  The internal codes for the bits in
     LISTWD are described in the MACREL/LINK User's Manual.				 _________________________

				     2-83
			  DESCRIPTIONS OF THE MODULES


     2.27  OVRS (Overlay 23)

     The overlay OVRS contains the routines that implement the  FIXTAB  and
     EXPUNGE directives.



     2.27.1  $FIXTAB

     The routine $FIXTAB implements the FIXTAB directive.   It  parses  the
     list of names that follows the directive.  It then searches the symbol
     table for each name and sets bit 2 of the its  flag  word  to  1.   If
     there  is  no  argument  list, it sets this bit for every entry in the
     symbol table.



     2.27.2  $EXPUNGE

     The  routine  $EXPUNGE  implements  the  EXPUNGE  directive.   It   is
     identical to $FIXTAB, except that instead of setting a bit, it unlinks
     the chunk from the symbol table that contains the symbol  and  returns
     it to freespace.



     2.28  OVRT (Overlay 24)

     The overlay OVRT contains the routines that (1) cause MACREL to  chain
     to the KREF and LINK programs and (2) implement the FIELD directive.



     2.28.1  LNKCHN

     Control passes  to  the  routine  LNKCHN  when  MACREL  has  completed
     assembly  and one or more of the C, L or G command string options were
     selected.  It performs the following tasks:

	  1.  Transfers control to KRFCHN if the /C option was selected, to
	      chain  to  KREF.  Otherwise, it scans for the /L or /G option
	      and chains to LINK.SV.

	  2.  (when chaining to LINK)

	      a.  Sets the altmode bit in the command decoder area.

	      b.  Deletes all options except LINK's G, H, S, V, W, and  0-9
		  options.  (This includes the equal sign (=) option.)

	      c.  Requests LINK to produce a .SV and a .MP  file  from  the
		  .RB file and the USR to load and run SYS:LINK.SV.



				     2-84
			  DESCRIPTIONS OF THE MODULES


     2.28.2  KRFCHN

     The  routine   KRFCHN   chains   to   SYS:KREF.SV   and   passes   the
     cross-reference  (.KF)  file  created  by  MACREL to the KREF program.
     KREF assigns the output file that it creates a .LT file name extension
     rather  than  the standard .LS OS/8 listing file name extension.  This
     is necessary to prevent the KREF  output  file  from  overwriting  the
     regular listing file.



     2.28.3  $FIELD

     The routine $FIELD implements the FIELD directive.   It  performs  the
     following tasks:

	  1.  Parses the expression following the FIELD keyword.

	  2.  Closes the current program section, if  it  is  unnamed,  and
	      begins  another  unnamed  program  section with a name of the
     	      form:  FLD:nn

     where:

	  nn	 is the absolute part of the expression



     2.29  OVRU (Overlay 25)

     The overlay OVRU contains the  routines  that  implement  the  .SBTTL,
     .TITLE, EJECT, RELOC, .PUSH and .POP directives.



     2.29.1  $SBTTL

     The routine $SBTTL implements the .SBTTL directive.   It  calls  SETIT
     (MAC24) to obtain a new title from the text that follows the directive
     and to insert it in SUBTL.  If this is pass 1, it sends this  subtitle
     along  with  the current page and line number to the table-of-contents
     file.  Otherwise, it ignores the directive and returns through BYEB to
     the ASEMLV routine (MAC24), which continues parsing the source file.



     2.29.2  $EJECT

     The routine $EJECT implements the EJECT directive.  It uses  the  same
     code  as  the .TITLE directive, except that it sets FORM to 1, so that
     the listing continues on a new page.




				     2-85
			  DESCRIPTIONS OF THE MODULES


     2.29.3  $TITLE

     The routine $TITLE implements the .TITLE directive.   It  calls  SETIT
     (MAC24) to obtain a new title from the text that follows the directive
     and to insert it in HEADING.



     2.29.4  $RELOC

     The routine $RELOC implements the RELOC directive.   It  performs  the
     following tasks:

	  1.  (if no expression follows the directive keyword -- that is, a
	      simple RELOC directive)

	      a.  Alters the current location counter  (PC)  to  the  value
		  PC+RELOK.

	  2.  (if an expression follows the directive keyword--that  is,  a
	      complex RELOC directive)

	      a.  Parses the expression and returns an error message if  it
		  is not an absolute expression.

	      b.  Stores  the  value  of  the  expression  in  the  current
		  location counter (PC).

	      c.  Sets RELOK to the  value  of  the  old  current  location
		  counter minus this new value.

	      d.  Stores the current location counter  in  BINARY  so  that
		  this  new  current location counter value will be printed
		  in the binary column of the assembly listing.



     2.29.5  $PUSH and $POP

     The two labels $PUSH and $POP are entry points  to  a  single  routine
     that  implements  the  .PUSH and .POP directives.  Entry through $PUSH
     causes the routine to set PSHTYP to a 1.  Entry  through  $POP  causes
     the  routine  to  set  PSHTYP  to a 0 (value of AC on entry).  It then
     parses a sequence of symbols and their values from the  argument  list
     and defines them if they are undefined.  It places (pushes) them on or
     removes (pops) them from the user stack (USRSTK (MACIO)) depending  on
     the  value of PSHTYP.  The routine generates an error if it detects an
     attempt to .PUSH or .POP a program section name.



     2.30  PAS2 (Overlay 16)

     The overlay PAS2 contains the pass 2 and pass  4  specific  code.   It

				     2-86
			  DESCRIPTIONS OF THE MODULES


     consists of the PUTBN, CHKFUL, PUTBT, GETFLG, BPUTX, CREFX, and MORCRF
     routines.



     2.30.1  PUTBN

     The routine PUTBN sends a new binary entry, together  with  its  2-bit
     flag  word to the binary output buffer.  It automatically starts a new
     flag word when necessary.



     2.30.2  CHKFUL

     The routine CHKFUL checks to see if the binary output buffer is  full.
     If the buffer is full, CHKFUL performs the following tasks:

	  1.  Requests QPUT (MACIO) to send the buffer of  binary  data  to
	      the .RB file.

	  2.  Resets the flag word mechanism so that the  next  2  bits  of
	      flag  information  start at the beginning of a new flag word.
	      (It ignores unused fields in the previous flag word.)

	  3.  Sets up the first (header) word of the binary  output  buffer
	      (0  for  Loader  Symbol  Dictionary (LSD) blocks and 4000 for
	      text blocks).

     If the output buffer is  not  full,  CHKFUL  returns  control  to  the
     calling routine.



     2.30.3  PUTBT

     The routine PUTBT inserts a word into the binary output buffer without
     updating the current flag word.  It is used for complicated constructs
     that require more than one word per flag entry.  These constructs  all
     have an LSD flag field code of 3 (see the discussion of the LSD in the
     MACREL/LINK User's Manual).     _________________________


				     NOTE

		   The first word of binary data is  always
		   sent  via a call to PUTBN so that FLG is
		   not set up.  Subsequent words of  binary
		   data are inserted using PUTBT.






				     2-87
			  DESCRIPTIONS OF THE MODULES


     2.30.4  GETFLG

     The routine GETFLG obtains a new flag word location and sets bit 11 to
     1.   (This will signify that the flag word is full when the successive
     left rotate instructions performed by CHKFUL cause this bit to set the
     link.)  The  flag  word  contains  six 2-bit flags as described in the
     MACREL/LINK User's Manual.     _________________________



     2.30.5  BPUTX

     The routine BPUTX sends a new binary entry, together  with  its  2-bit
     flag field to the binary output buffer.  It automatically starts a new
     flag word when necessary.  It performs the same task as  PUTBN  except
     that  it  ignores  bit  0  of  FLG, which (occasionally) is set when a
     literal value of 4003 (octal) is stored in FLG by OUTDATA (MAC24).



     2.30.6  CREFX

     The routine CREFX creates the cross-reference listing (KREF) file  and
     sends it to the output device during pass 4.



     2.30.7  MORCRF

     The routine MORCRF sends cross-reference information about literals to
     the cross-reference (KREF) file.

     Literals are assigned internal names that begin with  the  6-bit  code
     76.   The  second  character  is  either  L or V, indicating a KREF by
     location or by value respectively.  The second  word  of  the  literal
     name (characters 3 and 4) is the location or value, and character 6 is
     a  plus  (+)  if  the  literal  is  relocatable  (or  its  location is
     relocatable).

















				     2-88





























				    PART II

				     LINK






				   CHAPTER 3

				 INTRODUCTION



     3.1  INTRODUCTION

     LINK is the companion program to MACREL.  It converts the  relocatable
     binary  object  modules  created  by  MACREL into an executable memory
     image file.  LINK makes  two  passes  over  the  user-specified  input
     modules.   During  the  first pass, it creates the global symbol table
     (GST).  The GST contains all program section names and global  symbols
     used  by  the  input  modules.   During  the second pass, it reads the
     object modules and performs the following tasks:

	  o  Adjusts all address-dependent locations to correspond  to  the
	     relocation of program sections.

	  o  Resolves all global references within object modules.

	  o  Searches user-specified libraries for unresolved globals.

	  o  Creates an overlay structure, including the necessary  overlay
	     handler, according to the user's specifications.

	  o  Creates a memory image file load module  in  OS/8  save  image
	     format.   This  file  contains  a  core  control  block  (CCB)
	     followed by the linked and relocated object code.



     3.2  SYSTEM LAYOUT

     LINK consists of nine MACREL source modules.  The  LNKCAL  and  LNKMAN
     modules  contain two resident program sections.  The remaining modules
     (LNKALL, LNKBN1, LNKBN2, LNKCD, LNKMAP, LNKLSD,  and  LNKMSG)  contain
     the  program  sections  that operate as a system of MACREL overlays as
     described in the MACREL/LINK Reference Manual.  (This is  in  contrast		      ____________________________
     to the overlay system that is internal to MACREL.



     3.3  IMPLEMENTATION LANGUAGE

     LINK is written in MACREL assembly language and is capable of  linking
     itself.



     3.4  LABEL AND SYMBOL CONVENTIONS

				      3-1
				 INTRODUCTION


     Whenever possible, labels and symbols have been used that describe the
     function being performed or data being represented.  LINK does not use
     local labels or local symbols.



     3.5  ROUTINE CALLING CONVENTIONS

     Routines call subroutines using  a  JMS  instruction  and,  with  rare
     exceptions,  pass  the  appropriate parameters either in the AC at the
     time of the call, or in the memory locations that follow the  JMS,  or
     both.



     3.6  DATA FORMATS AND  REPRESENTATIONS

     LINK stores data in memory, using one of the following data formats:

	  o  12-bit value

	  o  15-bit pointer (see Section 1.6.2)

	  o  MACREL 6-bit characters (see Appendix A)

	  o  6-bit ASCII characters (see Appendix A)

	  o  OS/8 Command  Decoder  format  (refer  to  the  OS/8  Software							     ______________
	     Support Manual)	     ______________

	  o  Tables, as described in Section 3.7



     3.7  TABLES

     This section contains detailed descriptions of LINK's internal tables.



     3.7.1  Global Symbol Table (GST)

     The global symbol table consists of eight-word  entries.   Each  entry
     contains the information about one global symbol.  The table varies in
     length depending on the number of global symbols  and  the  amount  of
     memory  available.   Since  LINK  places  entries  in  the table as it
     encounters them, it must perform a sequential  search  to  retrieve  a
     particular  symbol.  Table 3-1 shows the format of an entry, and Table
     3-2 shows the type codes.






				      3-2
				 INTRODUCTION


				   Table 3-1
		       Global Symbol Table Entry Format

     ----------------------------------------------------------------------
     | Word |				Use				  |
     |------|-------------------------------------------------------------|
     |	    |								  |
     |   0  | char 0 / char 1	 char = character of symbol name	  |
     |   1  | char 2 / char 3		in MACREL 6-bit code		  |
     |   2  | char 4 / char 5						  |
     |	    |								  |
     |   3  | PC if the symbol is not declared .ENTRY, or transfer vector |
     |      | count (TRNCNT) if symbol is declared .ENTRY		  |
     |	    |								  |
     |   4  | bit							  |
     |	    |   0      field flag					  |
     |	    |		0 = word 5 does not contain an absolute field*	  |
     |	    |		1 = word 5 contains an absolute field*		  |
     |	    |	1      address flag					  |
     |	    |		0 = word 6 does not contain an absolute address*  |
     |	    |		1 = word 6 contains an absolute address*	  |
     |	    |	2      field reference pointer flag			  |
     |	    |		0 = field reference pointer OK			  |
     |	    |		1 = field reference pointer in error (same page	  |
     |	    |		    restriction)*				  |
     |	    |	3      address reference pointer flag			  |
     |	    |		0 = address reference pointer flag		  |
     |	    |		1 = address reference pointer in error		  |
     |	    |	4      definition flag					  |
     |	    |		0 = symbol is defined				  |
     |	    |		1 = symbol is undefined				  |
     |	    |	5-7    unused						  |
     |	    |								  |
     |	    |	8-11   type code (see Table 3-2)			  |
     |	    |								  |
     |   5  | field or pointer to GST (see word 4 bit 0)		  |
     |	    |								  |
     |   6  | address or offset (see word 4 bit 1)			  |
     |	    |								  |
     |   7  | bit							  |
     |	    |	0      transfer vector flag				  |
     |	    |		0 = no transfer vector needed			  |
     |	    |		1 = transfer vector needed			  |
     |	    |	1-4    unused						  |
     |	    |	5-7    level						  |
     |	    |	8-11   overlay						  |
     ----------------------------------------------------------------------
	* Relates to program section symbols only.







				      3-3
				 INTRODUCTION


				   Table 3-2
		     Global Symbol Table Symbol Type Codes

	      ---------------------------------------------------
	      | Code   |		Symbol Type		|
	      |--------|----------------------------------------|
	      |	       |					|
	      | 0      | FIELD					|
	      | 1      | .SECREF				|
	      | 2      | .ASECT					|
	      | 3      | .RSECT					|
	      | 4      | .FSECT					|
	      | 5      | .DSECT					|
	      | 6-7    | unused					|
	      | 10     | .XSECT					|
	      | 11     | .ZSECT					|
	      | 12-13  | unused					|
	      | 14     | .ENTRY					|
	      | 15     | .GLOBAL				|
	      | 16     | .EXTERNAL (stored as undefined global) |
	      | 17     | .ZTERNAL				|
	      ---------------------------------------------------	


     3.7.2  Binary Buffer Table (LDBUFS)

     The binary buffer table establishes  the  correspondence  between  the
     binary  buffers  and  the relative block addresses of the loader image
     file.  It begins at location 12000 and consists of one  to  thirty-two
     one-word entries.

     The number of entries in the table is proportional to  the  amount  of
     memory   fields   available   (see   Table   3-3).    Each   entry  is
     position-dependent and contains a loader image file block number.  For
     example,  the  first entry corresponds to the first buffer, the second
     entry corresponds to the second buffer, and so forth.

     The binary buffers function as windows  into  the  loader  image  file
     through  which the loaded program is written to the output file.  Each
     binary buffer is two pages (one OS/8 block) long.  The binary  buffers
     start  at  location  20000 except in 8K-word memory environments where
     they start at location 07000.

     LINK optimizes input/output operations by keeping a record of the last
     time each buffer was referenced.  When the buffer is to be loaded with
     new data, LINK uses the buffer that was  least  recently  used.   This
     allows data that is frequently referenced to reside in memory.








				      3-4
				 INTRODUCTION


				   Table 3-3
	     Number of Binary Buffers as a Function of Memory Size

			 -----------------------------
			 | Memory	 | Number of |
			 | Size		 | Buffers   |
			 |---------------|-----------|
			 |		 |	     |
			 | 8K		 |   1	     |
			 | 12K		 |   8	     |
			 | 16K		 |   16      |
			 | 20K		 |   24      |
			 | 24K		 |   32      |
			 | 28K		 |   32      |
			 | 32K		 |   32      |
			 -----------------------------



     3.7.3  Pointer Table (PTRTAB)

     The pointer table establishes the correspondence between the local LSD
     reference numbers used in the LSD text, and the address of that symbol
     in the GST.  It contains 256  (decimal)  one-word  entries.   The  nth
     entry  in PTRTAB contains the GST entry number of LSD symbol n.  Bit 0
     is set to a 1 if the entry is a reference that  is  inaccurate.   This
     means  that the program section name has an erroneous field or address
     value.



     3.7.4  Module Descriptor Table (MODTAB)

     The module descriptor table contains the file and overlay  information
     for  each  module  that  the  user specifies.  It consists of 1 to 128
     (decimal) three-word entries.  Each entry contains the  data  for  one
     input module.  The entries appear in ascending order both by level and
     by overlay within the level.  Library module entries reside at the end
     of  table,  because they are processed last and can only appear in the
     main level.  Table 3-4 shows the format of the table.



     3.7.5  .SECT Table (SECTAB)

     The .SECT table contains entries that describe  the  program  sections
     found  in  the  global  symbol  table (GST).  The table is used during
     memory allocation.  Each entry is six words long as described in Table
     3-5.






				      3-5
				 INTRODUCTION


				   Table 3-4
			Module Descriptor Table Format

     ----------------------------------------------------------------------
     |	   Word   |		    Use					  |
     |------------|-------------------------------------------------------|
     |		  |							  |
     |      0	  | bits						  |
     |	  	  |    0-7   block length				  |
     |	  	  |    8-11  device number				  |
     |		  |							  |
     |      1	  | starting block number				  |
     |		  |							  |
     |      2	  | bit							  |
     |	  	  |   0      library module flag			  |
     |	  	  |	      0 = entry is not for a library module	  |
     |	  	  |	      1 = entry is for a library module		  |
     |		  |							  |
     |	  	  |   1-4    unused					  |
     |	 	  |   5-7    level number				  |
     |	  	  |   8-11   overlay number				  |
     ----------------------------------------------------------------------


				   Table 3-5
			      .SECT Table Format

     ----------------------------------------------------------------------
     |  Word |			      Use				  |
     |-------|------------------------------------------------------------|
     |	     |								  |
     |	 0   | bit							  |
     |	     |   0	memory allocation flag				  |
     |       |		 0 = no memory allocated for this program section |
     |       |		 1 = memory allocated for this program section	  |
     |	     |								  |
     |       |   1-11 global symbol table entry number			  |
     |	     |								  |
     |	 1   | bit							  |
     |	     |   0	field flag					  |
     |       |		 0 = GST entry number of field restriction	  |
     |	     |	     	     in word 2					  |
     |	     |	 	 1 = absolute field value in word 2		  |
     |	     |								  |
     |	     |   1	address flag					  |
     |	     |	 	 0 = GST entry number of address restriction	  |
     |	     |	     	     in word 3					  |
     |	     |	 	 1 = absolute address in word 3			  |
     ----------------------------------------------------------------------
						 (continued on next page)





				      3-6
				 INTRODUCTION


			       Table 3-5 (Cont.)
			      .SECT Table Format

     ----------------------------------------------------------------------
     |  Word |			      Use				  |
     |-------|------------------------------------------------------------|
     |	     |								  |
     |	     |   2	field restriction flag				  |
     |	     |		 0 = no field restriction			  |
     |	     |	 	 1 = same field restriction			  |
     |	     |								  |
     |	     |   3	page restriction flag				  |
     |	     |	 	 0 = no page restriction			  |
     |	     |	 	 1 = same page restriction			  |
     |	     |								  |
     |	     |   4-10	unused						  |
     |	     |								  |
     |	     |   11	load flag					  |
     |	     |	 	 0 = program section loaded			  |
     |	     |	 	 1 = program section failed to load		  |
     |	     |								  |
     |   2   | GST entry number of field restriction (word 1, bit 0 = 0)  |
     |	     |								  |
     |	     | bit							  |
     |	     |   0	field flag					  |
     |	     |	 	 0 = field word is not in global symbol table	  |
     |	     |	 	 1 = field word is in global symbol table	  |
     |	     |								  |
     |	     |   1-11	GST entry number of field restriction		  |
     |	     |								  |
     |	     | absolute field (word 1, bit 0 = 1)			  |
     |	     |								  |
     |	     | bit							  |
     |	     |   0-6	unused						  |
     |	     |								  |
     |	     |   7-11	field						  |
     |	     |								  |
     |	 3   | GST entry number of address restriction (word 1, bit 1 = 0)|
     |	     |								  |
     |	     | bit							  |
     |	     |   0	address flag					  |
     |	     |		 0 = address is not in the global symbol table	  |
     |	     |	 	 1 = address is in the global symbol table	  |
     |	     |								  |
     |	     |   1-11	GST entry number of address restriction		  |
     |	     |								  |
     |	     | absolute address (word 1, bit 1 = 1)			  |
     |	     |								  |
     |	     | bit							  |
     |	     |   0-11	absolute address				  |
     ----------------------------------------------------------------------
						 (continued on next page)



				      3-7
				 INTRODUCTION


			       Table 3-5 (Cont.)
			      .SECT Table Format

     ----------------------------------------------------------------------
     |  Word |			      Use				  |
     |-------|------------------------------------------------------------|
     |	     |								  |
     |	 4   | bit							  |
     |	     |   0-2	(TYPE-2)& 7 (octal)				  |
     |	     |   3-4	unused						  |
     |	     |   5-7	level						  |
     |	     |   8-11	overlay						  |
     |	     |								  |
     |	 5   | length of program section				  |
     ----------------------------------------------------------------------



     3.7.6  Core Image Table (CIMAG, CIMAG1, CIMAG2, and CIMAGE)

     The core image table describes the available  memory  segments.   LINK
     maintains three versions of the table:  CIMAG, CIMAG1, and CIMAG2 (see
     Section 4.1).  They are used during memory allocation and are  updated
     in  the CIMAGE buffer area.  They consist of three-word entries in the
     form shown in Table 3-6.


				   Table 3-6
			    Core Image Table Format

		   ----------------------------------------			
		   | Word  |		Use		  |
		   |-------|------------------------------|
		   |	   |				  |
		   |  0    | bits			  |
		   |	   |    0-6 unused		  |
		   |	   |    7-11 field		  |
		   |	   |				  |
		   |  1    | starting address		  |
		   |	   |				  |
		   |  2    | length of the memory segment |
		   ----------------------------------------



     3.7.7  Overlay Transfer Vector (TRANVC)

     An overlay transfer vector contains the information required  to  load
     the  overlay and start execution of the specified routine.  An overlay
     transfer vector is four words long.  Table 3-7 shows the format of  an
     overlay transfer vector.




				      3-8
				 INTRODUCTION


				   Table 3-7
			Overlay Transfer Vector Format

	  -----------------------------------------------------------
	  | Word  |			Use			    |
	  |-------|-------------------------------------------------|
	  |	  |						    |
	  |  0	  | ISZ XFERV					    |
	  |	  |						    |
	  |  1	  | JMS I XFERV+1				    |
	  |	  |						    |
	  |  2	  | bit						    |
	  |	  |   0-1    field number (most significant bits)   |
	  |	  |   2-4    level number			    |
	  |	  |   5-8    overlay number			    |
	  |	  |   9-11   field number (least significant bits)  |
	  |	  |						    |
	  |  3	  |   address of entry point			    |
	  -----------------------------------------------------------

     NOTES

	  1.  XFERV is a  flag  word  that  the  overlay  handler  uses  to
	      determine  whether  execution  control will pass to the newly
	      loaded overlay using a JMP or a JMS instruction.  XFERV  will
	      contain  a  0,  if  a JMS instruction is to be used.  It will
	      contain a 1 (because of the ISZ XFERV instruction) if  a  JMP
	      instruction is to be used.

	  2.  XFERV+1 contains the address of the overlay  handler's  entry
	      point.

	  3.  The version 2A of  OVRDRV.MA  does  not  manage  overlays  in
	      fields  higher  than  field 7 and so does not use bits 0-1 of
	      word 2.



     3.7.8  User Overlay Level Data Table (QUSRLV)

     The user overlay level data table (QUSRLV) provides the information to
     create the overlay storage information table (OST) that resides in the
     core control block (CCB).  It consists of 4-word entries as defined in
     Table 3-8.


				     NOTE

		   The OST is used by the OS/8 file utility
		   program  FUTIL.  Neither MACREL nor LINK
		   uses this table.




				      3-9
				 INTRODUCTION


				   Table 3-8
			Overlay Level Data Table Format

		 ---------------------------------------------
		 | Word	 |		    Use		     |
		 |-------|-----------------------------------|
		 |	 |				     |
		 |  0	 | number of overlays in this level  |
		 |	 |				     |
		 |  1	 | bit				     |
		 |	 |   0-4    address of overlay area  |
		 |	 |   5-6    unused		     |
		 |	 |   7-11   field		     |
		 |	 |				     |
		 |  2	 | relative starting block number    |
		 |	 |				     |
		 |  3	 | length of overlay (in pages)	     |
		 ---------------------------------------------



     3.7.9  Overlay Level Information Table (LHDR)

     The overlay level information table contains the information that LINK
     uses  to  build  the  swap  table  (SWPTAB)  that  the  overlay driver
     (OVRDRV.MA) allocates.  LHDR contains eight four-word  entries.   Each
     entry  corresponds  to  one  of  the  eight possible overlay levels (0
     through 7).  Table 3-9 shows the format of an entry.


				   Table 3-9
		    Overlay Information Table Entry Format

     ----------------------------------------------------------------------
     | Word  |			Use					  |
     |-------|------------------------------------------------------------|
     |	     |								  |
     |	0    | bit							  |
     |	     |   0-6    unused						  |
     |	     |   7-11   field of level					  |
     |	     |								  |
     |	1    | address of level						  |
     |	     |								  |
     |	2    | relative block number of first overlay in level		  |
     |	     |								  |
     |	3    | length (in pages) of the overlay (All overlays in a level  |
     |	     | are the same length.)					  |
     ----------------------------------------------------------------------



     3.7.10  Main Binary Section Table (MBST)

     The main binary section table contains the program's memory allocation

				     3-10
				 INTRODUCTION


     data  and  is  constructed  from  the memory image file's core control
     block.  It consists of a number of 2-word and 4-word entries, as shown
     in Figure 3-1.  The table begins with a number of 2-word entries;  one
     for each memory field occupied  by  the  user's  program.   These  are
     followed  by  a  number  of  4-word  entries.   The 2-word entries are
     organized in descending order by field number.  Each entry series as a
     header for one or more of the 4-word entries.

	2-word entries  ----------------------------------------
	       |	| number of 4-word entries for field n |
	       |	|--------------------------------------|
	       |	|  pointer to first entry for field n  |---------
	       |	|--------------------------------------|	|
	       V	|	 counter for field n-1	       |	|	       |
			|--------------------------------------|	|
			|	 pointer for field n-1	       |-----	|
			|--------------------------------------|    |	|
			|		    .		       |    |	|
			|		    .		       |    |	|
			|		    .		       |    |	|
			|--------------------------------------|    V	|								    |
			|	  counter for field 0	       |    |	|
			|--------------------------------------|    |	|
			|	  pointer for field 0	       |    |	|
	4-word entries	|--------------------------------------|    |	V									|
	       |	|  field of this section (bits 7-11)   |<----	|
	       |	|--------------------------------------|	|
	       |	|	   starting address	       |	|
	       |	|--------------------------------------|	|
	       V	|   relative block of the image file   |	|	       |
			|--------------------------------------|	|
			|      number of records (pages)       |	|
			|--------------------------------------|	|
			|		    .		       |	|
			|		    .		       |	|
			|		    .		       |	|
			|--------------------------------------|	|
			|  field of this section (bits 7-11)   |<--------
			|--------------------------------------|
			|	   starting address	       |
			|--------------------------------------|
			|   relative block of the image file   |
			|--------------------------------------|
			|	   number of records	       |
			|--------------------------------------|
			|		    .		       |
			|		    .		       |
			|		    .		       |
			----------------------------------------
						       ML-032-80

		  Figure 3-1 Main Binary Section Table Layout



				     3-11
				 INTRODUCTION


     3.7.11  Memory Segment Control Double Words

     Table 3-10 shows the format of the memory segment control  word  pairs
     contained in the core control block.


				  Table 3-10
		Memory Segment Control Double Word Entry Format

	     -----------------------------------------------------
	     | Word   |			Use			 |
	     |--------|------------------------------------------|
	     |	      |						 |
	     |  0     | starting address of segment		 |
	     |	      |						 |
	     |	1     |	bit					 |
	     |	      |   0	 unused				 |
	     |	      |   1-5    number of pages in this segment |
	     |	      |   6-10   5-bit field number of the form: |
	     |	      |						 |
	     |	      |				abcde		 |
	     |	      |						 |
	     |	      |		  encoded as:			 |
	     |	      |						 |
	     |	      |			    bit 6	10	 |
	     -----------------------------------------------------



     3.7.12  Library Table (LIBTB)

     The library table is a table of bit flags that specifies which modules
     (LSDs)  in  the user-specified library files are to be included in the
     load image file (see Figure 3-2).  Each LSD in a file  is  assigned  a
     bit  in  LIBTB.   The order of bit assignment is that specified by the
     user to the Command Decoder (stored in MODTAB).   The  bit  flags  for
     each file begin on a word boundary starting with the least significant
     bit (bit 11).  The bits are assigned from least  significant  to  most
     significant  within a word in increasing word addresses.  For example,
     the first LSD in the first library file is assigned to bit 11  of  the
     first  word in LIBTB.  Each bit that is set to a 1 indicates an LSD to
     be included in the memory image.



     3.8  DEFAULT CONDITIONS

     The following rules define LINK's default operating conditions:

	  1.  Unless otherwise specified by the software memory  size,  all
	      of memory not occupied by LINK and OS/8 code is available for
	      tables and buffers.



				     3-12
				 INTRODUCTION


		    bit		   bit
		     0			   11
		    -------------------------
     LIBTB (06000)  | | | | | | | | | | | | | first 12 LSDs \
		    |-----------------------|		     \
		    | | | | | | | | | | | | | next 12 LSDs    \
		    |-----------------------|		       \  first
		    |		.	    |		       /  library
		    |		.	    |		      /   file
		    |		.	    |		     /
		    |-----------------------|		    /
		    | | | | | | | | | | | | | first 12 LSDs \
		    |-----------------------|		     \
		    |		.	    |		      \  second
		    |		.	    |		      /  library
		    |		.	    |		     /	 file
		    |-----------------------|		    /
	LIBTB+177   | | | | | | | | | | | | |
		    -------------------------
				    ML-033-30

			Figure 3-2 Library Table Layout


	  2.  Unless otherwise specified in a Command Decoder input line or
	      in an input module:

	      a.  The size of memory for the object program is the same  as
		  the size of memory available for use by LINK.

	      b.  The object program will  not  load  into  locations  7600
		  through 7777 of any memory field.

	      c.  The object program will contain no overlays.

	      d.  The  empty  memory  of  the  object   program   will   be
		  initialized to contain zeros.

	      e.  No library other than LNKLIB.RB (if it  exists  on  SYS:)
		  will be scanned to resolve undefined symbols.

	      f.  The default starting address  is  00200  for  the  object
		  program.

	      g.  The job status word will be created by the loader for the
		  object program.

	      h.  Locations 0-1777 of field 0 and field 1 will be allocated
		  to the object program.

	      i.  Every memory field that can be allocated  to  the  object
		  program shall be (if necessary) allocated.



				     3-13
				 INTRODUCTION


     3.9  LINK ERROR AND EXCEPTION REPORTING

     LINK sends error messages to the console terminal as  it  creates  the
     memory  image  file.  Except where indicated in the MACREL/LINK User's							 __________________
     Manual, the errors are fatal.  When LINK encounters a fatal error,  it     ______
     returns control to the OS/8 Monitor.

















































				     3-14






				   CHAPTER 4

			  DESCRIPTIONS OF THE MODULES


     This chapter describes the  major  operations  performed  by  each  of
     LINK's  modules.   They  are presented in alphabetical order by module
     name.



     4.1  LNKALL

     The LNKALL overlay allocates memory to the user's program, builds  any
     specified  overlay  structures  and sets up the following three memory
     image tables:

	  o  CIMAG contains the master memory  image  and  resides  on  the
	     system  device  (blocks 40 and 41 (octal)).  It is accessed by
	     the WRICIM and RDCIM routines.

	  o  CIMAG1 contains the current overlay's memory image and is  the
	     primary working image used for allocating memory to the user's
	     program.  It  resides  in  location  10000  to  10777  and  is
	     accessed by the WRCIM1 and RDCIM1 routines.

	  o  CIMAG2 contains the current overlay level's memory image.   It
	     resides  in  locations  11000  to 11777 and is accessed by the
	     WRCIM2 and RDCIM2 routines.

     During memory allocation, these tables are read into and written  from
     the buffer CIMAGE (locations 06600 to 07577).  They are updated as the
     memory image table changes.

     LNKALL attempts to fit all program sections into available memory.  If
     it  cannot  fit  a  program  section  into the memory that remains, it
     attempts to optimize the memory layout by:

	  o  Deallocating memory from all program sections in  the  current
	     overlay.

	  o  Reordering the allocation list so that the name of the program
	     section that did not fit is at the top of the list.

	  o  Reallocating memory to the program sections according  to  the
	     reordered list.

     When done, LNKALL passes control to LNKCAL to call the LNKMAP overlay.

     LNKALL performs the following tasks:


				      4-1
			  DESCRIPTIONS OF THE MODULES


	  1.  Sets up the memory image  table  (CIMAG)  to  include  memory
	      fields 0 and 1.

	  2.  Allocates memory to the user's program as follows:

	      a.  Initializes relevant pointers and counters and  the  user
		  overlay level data table (QUSRLV).

	      b.  Writes the current contents of CIMAGE  to  CIMAG  and  to
		  CIMAG2.

	      c.  Obtains the  highest  unallocated  program  section  from
		  SECTAB.   If  this  program  section  is  not part of the
		  current level or overlay, LNKALL saves current  level  or
		  overlay information:

		  (1)  If an overlay is being changed, LNKALL reads a  copy
		       of CIMAG2 into CIMAGE for use as CIMAG1.

		  (2)  If a level is being changed, LNKALL checks that  the
		       old level:

		       o  Resides in one memory field if it is not the main
			  level.

		       o  Has no intervening program section from  a  lower
			  level.

		       o  Starts at an address that is a  multiple  of  400
			  (octal).

			  If  the  conditions  (above)  are  true,   LNKALL
			  updates  QUSRLV  and  copies  CIMAGE to CIMAG and
			  CIMAG2.  If any of these conditions are not true,
			  LNKALL  updates the contents of CIMAGE, copies it
			  to CIMAG2 and attempts  to  allocate  memory  for
			  that level again.

	      d.  Resolves  any  field  restrictions  that  apply  to  this
		  program  section.   If  this  is not possible, processing
		  continues with Step i (below).

	      e.  Resolves any address  restrictions  that  apply  to  this
		  program  section.   If  this  is not possible, processing
		  continues with Step i (below).

	      f.  Allocates memory to the program section.  If the  section
		  does not fit, it:

		  (1)  Deallocates  memory  for  all  previously  allocated
		       sections.

		  (2)  Inserts the section that did not fit at the  top  of
		       SECTAB.

				      4-2
			  DESCRIPTIONS OF THE MODULES


		  (3) Reinitializes the pointers to SECTAB.

		  (4) Continues processing with Step c (above).

	      g.  Flags the program section as being allocated and  updates
		  CIMAG1  to  reflect  the  successful  allocation  of  the
		  program section.

	      h.  Allocates  memory  to  all  program  sections  that   are
		  restricted  to  depend  on  this program section (Steps e
		  through g).  (It ignores program sections that cannot  be
		  allocated because of unallocated restrictions.)

	      i.  Advances necessary pointers and counters.  If  there  are
		  any  program  sections  left  to  allocate,  it continues
		  processing with Step c (above).  If  there  are  no  more
		  program  sections  to allocate, processing continues with
		  Step 3.

	  3.  Resolves all entry point and global symbol addresses  in  the
	      GST   if  the  user  did  not  request  a  memory  load  map.
	      Otherwise, it passes control back to LNKCAL to start creating
	      the load map.



     4.2  LNKBN1 AND LNKBN2

     The overlays LNKBN1 and LNKBN2 create a memory  image  of  the  object
     program  (if  requested)  and  starts  the  program if the G option is
     specified.  LNKALL calls LNKBN1 after LNKMAP generates the memory load
     map.  When LNKBN1 completes its tasks, it calls LNKBN2.

     The overlays perform the following tasks:

	  1.  Build the memory control block for the user's program.

	  2.  Modify  the  user  overlay  level  data  table  (QUSRLV)   to
	      determine  the  starting  block  in the file that begins each
	      overlay level.

	  3.  Send the memory control block data (from Step 1) and the user
	      overlay level data (from Step 2) to the output (.SV) file.

	  4.  Create the main binary section table  (MBST)  from  the  core
	      control block (CCB).

	  5.  Create the load image relative block number table (LHDR)  for
	      the main level (level 0) and overlay levels 1 through 7.

	  6.  Build a transfer vector table if  the  user  is  creating  an
	      overlay  structure.   (The overlay driver routine (OVRDRV.MA)
	      must be specified in the command line.)


				      4-3
			  DESCRIPTIONS OF THE MODULES


	  7.  Perform the following steps, processing the input modules for
	      the  second  time  (pass  2)  to  create the program's memory
	      image:

	      a.  Read a bufferful of data from an input  module  into  the
		  input buffer.

	      b.  Perform Step d (below) if this module is not in a library
		  file.

	      c.  Use LIBTB to determine  if  the  current  piece  of  this
		  library  is required.  If it is not required, the current
		  LSD and text is discarded and this step is repeated.   If
		  the piece is required, processing continues with the next
		  step.  When it has scanned the library  file  completely,
		  processing continues with Step f (below).

	      d.  Initialize the pointer table, then process  the  LSD  for
		  the  current module (or piece of a library) to equate LSD
		  numbers to GST numbers.

	      e.  Produce the corresponding part (Step  d)  of  the  memory
		  image  file  (.SV  file) from the relocatable part of the
		  relocatable binary (.RB) input module or library piece.

	      f.  (LNKBN2) advances its pointers to the next piece if  this
		  module  is  a  library file and processing continues with
		  Step c (below).  If the module is not a library  file  or
		  if  the  library  file  has  been fully processed, LNKBN2
		  advances all module pointers to the  next  input  module.
		  If  there is another module to read, processing continues
		  with Step a.  Otherwise, processing  continues  with  the
		  next step.

	      g.  Close the output file.

	      h.  Chain to the OS/8 absolute loader (ABSLDR.SV) to load and
		  start  the  program  if  the user specified the G option.
		  Otherwise it exits to the OS/8 Monitor.



     4.3  LNKCAL

     The module LNKCAL consists of two program sections.  The first section
     is  the  master  overlay  caller.  It consists of a series of jumps to
     LINK's various overlays.  The second program section  is  the  overlay
     driver.   This  is  the  code  that reads the appropriate overlay into
     memory and transfers control to it.  It is the standard overlay driver
     found in OVRDRV.MA.





				      4-4
			  DESCRIPTIONS OF THE MODULES


     4.4  LNKCD

     The LNKCD overlay accomplishes all interfacing between the program and
     the  OS/8  Command  Decoder.   It  obtains  the I/O specifications and
     options, and determines the amount of memory  available.   When  done,
     LNKCD passes control to LNKCAL to call the LNKLSD overlay.

     It performs the following tasks:

	  1.  Clears  the  temporary  map  file  (MFILE)  information   and
	      temporary  output file (OFILE) information tables, determines
	      the size of available memory, and initializes the pointers to
	      MTAB  and  NLTAB.   (These  are  temporary  working copies of
	      MODTAB and NULTAB respectively.)

	  2.  Calls the Command Decoder  to  obtain  the  I/O  and  control
	      specifications.

	  3.  Verifies and saves the memory image file and memory load  map
	      file specifications if they were specified.

	  4.  Obtains the  Command  Decoder  options,  verifies  them,  and
	      passes  control  to  the  routines that perform the setup for
	      each option.

	  5.  Places the input module specifications in the module table.

	  6.  Processes the C, D, and V options if specified.

	  7.  Processes the G option and the ESC terminator.  If  it  finds
	      either,   it   continues  processing  with  Step  8  (below).
	      Otherwise, it continues processing with Step 2 (above).

	  8.  Includes the contents of the library file  LNKLIB.RB  in  the
	      module table if the file resides on the system (SYS:) device.

	  9.  Determines the size  of  the  binary  buffer  table,  section
	      table, and global symbol table.

	 10.  Checks for the T option and processes it if BATCH is running.

	 11.  Returns control to the LNKCAL module to start pass 1.



     4.5  LNKMAN

     LNKMAN is a module that contains two resident program sections, LNKMAN
     and  PAGED.   They  contain the commonly used subroutines described in
     Table 4-1 and the page 0 variables.





				      4-5
			  DESCRIPTIONS OF THE MODULES


				   Table 4-1
			      Routines in LNKMAN

     ----------------------------------------------------------------------
     |  Routine	     |		      Description			  |
     |---------------|----------------------------------------------------|
     |		     |							  |
     |  TTYHAN	     | Sends messages to the terminal.			  |
     |		     |							  |
     |	TTYO	     | Sends a character to the terminal.		  |
     |		     |							  |
     |	CRLF	     | Sends a RETURN/LF combination to the terminal.	  |
     |		     |							  |
     |	OS8ER	     | Sends system errors to the terminal.		  |
     |		     |							  |
     |	EROUT	     | Sends fatal error messages to the terminal  during |
     |		     | pass 1.						  |
     |		     |							  |
     |	FERR	     | Sends fatal error messages to the terminal.	  |
     |		     |							  |
     |	NFERR	     | Sends non-fatal error messages to the terminal.	  |
     |		     |							  |
     |	IPTRTB	     | Initializes the pointer  table  that  equates  LSD |
     |		     | numbers to GST numbers.				  |
     |		     |							  |
     |	IOHAN	     | Interfaces I/O device handlers.  It can:		  |
     |		     |      o  Fetch a handler.				  |
     |		     |      o  Check for end of file.			  |
     |		     |	    o  Issue a call to a handler.		  |
     |		     |							  |
     |	GETREF	     | Retrieves a GST  entry  number  from  the  pointer |
     |		     | table.						  |
     |		     |							  |
     |	PROBOT	     | Processes both the LSD preface and the LSD  of  an |
     |		     | input module.					  |
     |		     |							  |
     |	INQIRE	     | Determines if a specified  device  handler  is  in |
     |		     | memory.						  |
     |		     |							  |
     |	REMOD	     | Reads in four blocks of data from an input module. |
     |		     |							  |
     |	IMPT	     | Initializes the input  module  table  pointer  and |
     |		     | counter.						  |
     |		     |							  |
     |	ADVPTR	     | Advances the module  table  pointer  to  the  next |
     |		     | input module.					  |
     |		     |							  |
     |	PUTGST	     | Inserts the contents of the  AC  into  the  global |
     |		     | symbol table.					  |
     |		     |							  |
     |	NXTBLK	     | Scans a library file for the  next  group  of  LSD |
     |		     | block(s) of an input file.			  |
     ----------------------------------------------------------------------
						 (continued on next page)

				      4-6
			  DESCRIPTIONS OF THE MODULES


			       Table 4-1 (Cont.)
			      Routines in LNKMAN

     ----------------------------------------------------------------------
     |  Routine	     |		      Description			  |
     |---------------|----------------------------------------------------|
     |		     |							  |
     |	TSTEND	     | Tests for the end of an input file.		  |
     |		     |							  |
     |	SKPLIB	     | Skips over a piece of a library.			  |
     |		     |							  |
     |	CGSTA	     | Calculates the address of an entry in  the  global |
     |		     | symbol  table,  using  the GST entry number in the |
     |		     | AC.						  |
     |		     |							  |
     |	PROLSD	     | Processes the contents of an LSD.		  |
     |		     |							  |
     |	GETLSD	     | Obtains a word from an LSD.			  |
     |		     |							  |
     |	ILSDP	     | Advances the LSD pickup pointer used in GETLSD  to |
     |		     | the next entry in the LSD.			  |
     |		     |							  |
     |	INCPTR	     | Advances a pointer into the global symbol table to |
     |		     | the next entry in the table.			  |
     |		     |							  |
     |	PROHDR	     | Processes the  LSD  header,  by  passing  the  LSD |
     |		     | preface.						  |
     |		     |							  |
     |	SEARCH	     | Searches the GST for a symbol.			  |
     |		     |							  |
     |	LOOK	     | Performs the actual symbol table  search  for  the |
     |		     | SEARCH subroutine (above).			  |
     |		     |							  |
     |	TSTBOT	     | Tests for the bottom (end) of  the  global  symbol |
     |		     | table.						  |
     |		     |							  |
     |	GETGST	     | Obtains a word from the global symbol table.	  |
     |		     |							  |
     |	OPRINT	     | Sends the contents of the AC  (in  octal)  to  the |
     |		     | terminal.					  |
     |		     |							  |
     |	PUTPTR	     | Inserts a GST entry index into the  pointer  table |
     |		     | (PTRTAB).					  |
     |		     |							  |
     |	SSEC	     | Searches the section table (SECTAB) for  the  data |
     |		     | in the AC.					  |
     |		     |							  |
     |	KEYBRD	     | Implements the CTRL/O, CTRL/C, CTRL/Q, and  CTRL/S |
     |		     | sequences for the TTYO subroutine.		  |
     |		     |							  |
     |	FIXCHR	     | Converts a backslash (\) to a  period  (.)  and  a |
     |		     | left  square  bracket ([) to a dollar ($) sign for |
     |		     | printing in the symbol table listing.		  |
     ----------------------------------------------------------------------

				      4-7
			  DESCRIPTIONS OF THE MODULES


     4.6  LNKLSD

     The overlay LNKLSD creates the global symbol table (GST)  and  program
     section  table  (SECTAB) from the loader symbol dictionaries (LSDs) of
     the input modules.  It begins by processing all  nonliterary  modules.
     Thereafter, it searches the user specified libraries (and LNKLIB.RB if
     it exists) to resolve any undefined symbols.

     LNKLSD is called by LNKCAL after all input modules have been specified
     to  LNKCD.   When  done,  LNKLSD  passes control to LNKCAL to call the
     LNKALL overlay.

     It performs the following tasks:

	  1.  Initializes various pointers and counters.

	  2.  Obtains an input module  descriptor  from  the  module  table
	      (MODTAB)  and  continues  processing with Step 3 (below).  If
	      this is  a  library  module,  it  ignores  it  and  continues
	      processing with Step 6 (below).

	  3.  Processes the LSD header:

	      a.  Checks that the file is a relocatable binary (.RB) file.

	      b.  Checks the RB specification level (LSD preface code 4).

	      c.  Obtains the starting address and job status word (JSW).

	  4.  Processes the LSD text:

	      a.  Obtains a symbol from the LSD.

	      b.  Searches the GST for the symbol.  If it does not find the
		  symbol, it enters the symbol in the GST.  If it finds the
		  symbol, it enters  the  program  section  in  SECTAB  and
		  checks   for  a  conflict  between  this  definition  and
		  previous  definitions.   If   there   is   no   conflict,
		  processing   continues   with  Step  c.   Otherwise,  the
		  conflict will eventually  cause  a  duplicate  definition
		  error.

	      c.  Places an index to the GST entry in the pointer table.

	      d.  Processes the next LSD entry beginning at Step a (above).
		  Otherwise, it continues processing with Step 5.

	  5.  Resolves all forward references in the GST.

	  6.  Advances the pointers into  the  module  table.   If  another
	      module  exists,  processing  continues  with  Step 2 (above).
	      Otherwise, processing continues with the next step.

	  7.  Scans the library modules as follows:

				      4-8
			  DESCRIPTIONS OF THE MODULES


	      a.  Initializes necessary pointers and counters.

	      b.  Obtains an input module descriptor from the module table.
		  If  it  is a library module, it continues processing with
		  Step c.  Otherwise, it continues processing with  Step  j
		  (below).

	      c.  Checks the appropriate  library  table  (LIBTB)  word  to
		  determine  if  this  piece  of the library resides in the
		  GST.  If it does, it ignores this  module  and  continues
		  processing  with  Step  g  (below).  Otherwise processing
		  continues with the next step.

	      d.  Reads the LSD for this piece of the library, checking the
		  LSD  header's  .RB  specification level (LSD preface code
		  4).

	      e.  Scans the  LSD  checking  that  each  symbol  resolves  a
		  previously  undefined  symbol.   If  it  cannot resolve a
		  symbol,  processing  continues  with  Step   g   (below).
		  Otherwise processing continues with the next step.

	      f.  Processes the LSD using Steps 4 and 5 (above).

	      g.  Advances all necessary pointers to process the next piece
		  of  the  library  (Step  c  above).   If there is no more
		  library input, processing continues with the next step.

	      h.  Processes undefined symbols that remain (the next  step).
		  If  there  are  no  more  symbols to define, it continues
		  processing with Step 8 (below).

	      i.  Determines if any symbol was resolved during the  current
		  pass  over  this  library.   If  this is true, processing
		  continues with Step  c  (above).   Otherwise,  processing
		  continues with the next step.

	      j.  Advances all necessary pointers and counters.   If  there
		  is another input module, processing continues with Step b
		  (above).  Otherwise, it displays all undefined symbols on
		  the terminal and continues processing with the next step.

	  8.  Adjusts all pointers in SECTAB to point forward  to  the  GST
	      word that contains the program section restriction (if any).

	  9.  Sorts  independent  program  sections  that  restrict   other
	      program sections so they reside at the top of their overlay.

	 10.  Sorts the null table (NULTAB) by field and page so  that  the
	      first entry contains the lowest field and page.

	 11.  Returns control to LNKCAL to start the allocating  memory  to
	      the user's program.


				      4-9
			  DESCRIPTIONS OF THE MODULES


     4.7  LNKMSG

     The overlay LNKMSG contains the error reporting routines for  most  of
     the  fatal  errors  that  LINK encounters.  It also contains the error
     message text.



     4.8  LNKMAP

     The overlay LNKMAP creates a load map of the  program  (if  requested)
     while  resolving  entry  point and global symbol addresses in the GST.
     It obtains the starting address, job status word, and memory load  map
     file I/O specifications from the Command Decoder.

     LNKMAP is called by LNKCAL after LNKALL has allocated memory  for  all
     program  sections.  When done, LNKMAP passes control to LNKCAL to call
     the LNKBN1 overlay.

     It performs the following tasks:

	  1.  Sets up the user-provided starting address if  the  S  option
	      was specified.

	  2.  Sets up the user-provided job status  word  (JSW)  if  the  W
	      option was specified.

	  3.  Produces  a  memory  load  map,  if  the  user  provided   an
	      appropriate   file   specification.    LNKMAP   performs  the
	      following steps:

	      a.  Sorts the program  section  table  (SECTAB)  by  address,
		  field, and overlay level.

	      b.  Sends all undefined and absolute global  symbols  to  the
		  memory load map file.

	      c.  Obtains a SECTAB pointer into the GST.

	      d.  Sends the program section's name, value,  and  length  to
		  the memory load map file.

	      e.  Resolves the program section's  entry  point  and  global
		  symbol  addresses  in  the  GST  and  sends the names and
		  values to the memory load map file.

	      f.  Performs Steps c through e for all entries in SECTAB.

	      g.  Sends the user-provided starting address and  job  status
		  word to the memory load map file.

	  4.  Passes  control  back  to  LNKCAL  to  start  generating  the
	      program's memory image.


				     4-10






				  APPENDIX A

				CHARACTER SETS



     Table A-1 shows the special 6-bit character set  used  by  MACREL  for
     most  symbol  table  storage.  Table  A-2 shows the standard 6-bit and
     7-bit ASCII character set used by both MACREL and LINK for  all  other
     operations.


				   Table A-1
		     MACREL Special 6-bit Character Codes

     ----------------------------------------------------------------------
     |   Code		 |		Meaning				  |
     |-------------------|------------------------------------------------|
     |			 |						  |
     |	0		 | padding					  |
     |  1-32		 | A through Z					  |
     |	33		 | $ (dollar sign)				  |
     |  34		 | . (period)					  |
     |  35		 | reserved					  |
     |  36 or 76	 | extended symbol name definition		  |
     |  37		 | reserved					  |
     |  40		 | reserved					  |
     |  41-72		 | $A through $Z (if first character in symbol)	  |
     |  60-71		 | 0 through 9 (if not first character in symbol) |
     ----------------------------------------------------------------------


				   Table A-2
			      ASCII Character Set

     ----------------------------------------------------------------------
     |	7-Bit | 6-Bit |  Character/  |		Remarks			  |
     |	Octal | Octal | Control Code |					  |
     |--------|-------|--------------|------------------------------------|
     |	      |	      |		     |					  |
     |	000   |	      |   NUL	     | Fill character - ignored on input  |
     |	001   |	      |   SOH	     |					  |
     |	002   |	      |   STX	     |					  |
     |	003   |	      |   ETX	     | CTRL/C - Return control to monitor |
     |	004   |	      |   EOT	     |					  |
     |	005   |	      |   ENQ	     |					  |
     |	006   |	      |   ACK	     |					  |
     |	007   |	      |   BEL	     | CTRL/G - Sound audible signal	  |
     |	010   |	      |   BS	     |					  |
     ----------------------------------------------------------------------
						 (continued on next page)

				      A-1
				CHARACTER SETS


			       Table A-2 (Cont.)
			      ASCII Character Set

     ----------------------------------------------------------------------
     |	7-Bit | 6-Bit |  Character/  |		Remarks			  |
     |	Octal | Octal | Control Code |					  |
     |--------|-------|--------------|------------------------------------|
     |	      |	      |		     |					  |
     |	011   |	      |   HT	     | CTRL/I - HT (horizontal tab)	  |
     |	012   |	      |   LF	     | CTRL/J - LF (new line)		  |
     |	013   |	      |   VT	     | CTRL/K - VT (vertical tab)	  |
     |	014   |	      |   FF	     | CTRL/L - FF (form feed)		  |
     |	015   |	      |   CR	     | CTRL/M - CR (cursor or carriage	  |
     |	      |	      |	             | 		   return)		  |
     |	016   |	      |   SO	     |					  |
     |	017   |	      |   SI	     | CTRL/O - Abort current terminal	  |
     |	      |	      |		     | 		output			  |
     |	020   |	      |   DLE	     |					  |
     |	021   |	      |   DC1	     | CTRL/Q - Disable terminal output	  |
     |	022   |	      |   DC2	     |					  |
     |	023   |	      |   DC3	     | CTRL/S - Enable terminal output	  |
     |	024   |	      |   DC4	     | CTRL/T - Display job status	  |
     |	025   |	      |   NAK	     | CTRL/U - Delete current input line |
     |	026   |	      |   SYN	     | CTRL/V				  |
     |	027   |	      |   ETB	     | CTRL/W				  |
     |	030   |	      |   CAN	     | CTRL/X				  |
     |	031   |	      |   EM	     | CTRL/Y				  |
     |	032   |	      |   SUB	     | CTRL/Z - End of file		  |
     |	033   |	      |   ESC	     | ALTMODE				  |
     |	034   |	      |   FS	     |					  |
     |	035   |	      |   GS	     |					  |
     |	036   |	      |   RS	     |					  |
     |	037   |	      |   US	     |					  |
     |	040   |  40   |   SP	     | Space				  |
     |	041   |  41   |   !	     | Exclamation point		  |
     |	042   |  42   |   "	     | Quotation mark			  |
     |	043   |  43   |   #	     |					  |
     |	044   |  44   |   $	     | Dollar sign			  |
     |	045   |  45   |   %	     | Percent sign			  |
     |	046   |  46   |   &	     | Ampersand			  |
     |	047   |  47   |   '	     | Apostrophe			  |
     |	050   |  50   |   (	     | Left parenthesis			  |
     |	051   |  51   |   )	     | Right parenthesis		  |
     |	052   |  52   |   *	     | Asterisk				  |
     |	053   |  53   |   +	     | Plus sign			  |
     |	054   |  54   |   ,	     | Comma				  |
     |	055   |  55   |   _	     | Hyphen or minus sign		  |
     |	056   |  56   |   .	     | Period				  |
     |	057   |  57   |   /	     | Slash (right)			  |
     |	060   |  60   |   0	     |					  |
     |	061   |  61   |   1	     |					  |
     |	062   |  62   |   2	     |					  |
     ----------------------------------------------------------------------
						 (continued on next page)

				      A-2
				CHARACTER SETS


			       Table A-2 (Cont.)
			      ASCII Character Set

     ----------------------------------------------------------------------
     |	7-Bit | 6-Bit |  Character/  |		Remarks			  |
     |	Octal | Octal | Control Code |					  |
     |--------|-------|--------------|------------------------------------|
     |	      |	      |		     |					  |
     |	063   |  63   |   3	     |					  |
     |	064   |  64   |   4	     |					  |
     |	065   |  65   |   5	     |					  |
     |	066   |  66   |   6	     |					  |
     |	067   |  67   |   7	     |					  |
     |	070   |  70   |   8	     |					  |
     |	071   |  71   |   9	     |					  |
     |	072   |  72   |   :	     | Colon				  |
     |	073   |  73   |   ;	     | Semicolon			  |
     |  074   |  74   |   <	     | Left angle bracket or less than	  |
     |	      |	      |		     | sign				  |
     |	075   |  75   |   =	     | Equals sign			  |
     |	076   |  76   |   >	     | Right angle bracket or greater	  |
     |	      |	      |		     | than sign			  |
     |	077   |  77   |   ?	     | Question mark			  |
     |	100   |  00   |   @	     | At sign (null in 6-bit)		  |
     |	101   |  01   |   A	     |					  |
     |	102   |  02   |   B	     |					  |
     |	103   |  03   |   C	     |					  |
     |	104   |  04   |   D	     |					  |
     |	105   |  05   |   E	     |					  |
     |	106   |  06   |   F	     |					  |
     |	107   |  07   |   G	     |					  |
     |	110   |  10   |   H	     |					  |
     |	111   |  11   |   I	     |					  |
     |	112   |  12   |   J	     |					  |
     |	113   |  13   |   K	     |					  |
     |	114   |  14   |   L	     |					  |
     |	115   |  15   |   M	     |					  |
     |	116   |  16   |   N	     |					  |
     |	117   |  17   |   O	     |					  |
     |	120   |  20   |   P	     |					  |
     |	121   |  21   |   Q	     |					  |
     |	122   |  22   |   R	     |					  |
     |	123   |  23   |   S	     |					  |
     |	124   |  24   |   T	     |					  |
     |	125   |  25   |   U	     |					  |
     |	126   |  26   |   V	     |					  |
     |	127   |  27   |   W	     |					  |
     |	130   |  30   |   X	     |					  |
     |	131   |  31   |   Y	     |					  |
     |	132   |  32   |   Z	     |					  |
     |	133   |  33   |   [	     | Left square bracket		  |
     |	134   |  34   |   \	     | Backslash			  |
     ----------------------------------------------------------------------
						 (continued on next page)

				      A-3
				CHARACTER SETS


			       Table A-2 (Cont.)
			      ASCII Character Set

     ----------------------------------------------------------------------
     |	7-Bit | 6-Bit |  Character/  |		Remarks			  |
     |	Octal | Octal | Control Code |					  |
     |--------|-------|--------------|------------------------------------|
     |	      |	      |		     |					  |
     |	135   |  35   |   ]	     | Right square bracket		  |
     |	136   |  36   |   ^	     | Circumflex			  |
     |	137   |  37   |   _	     |					  |
     |	140   |  40   |   `	     | Grave accent			  |
     |	141   |  41   |   a	     |					  |
     |	142   |  42   |   b	     |					  |
     |	143   |  43   |   c	     |					  |
     |	144   |  44   |   d	     |					  |
     |	145   |  45   |   e	     |					  |
     |	146   |  46   |   f	     |					  |
     |	147   |  47   |   g	     |					  |
     |	150   |  50   |   h	     |					  |
     |	151   |  51   |   i	     |					  |
     |	152   |  52   |   j	     |					  |
     |	153   |  53   |   k	     |					  |
     |	154   |  54   |   l	     |					  |
     |	155   |  55   |   m	     |					  |
     |	156   |  56   |   n	     |					  |
     |	157   |  57   |   o	     |					  |
     |	160   |  60   |   P	     |					  |
     |	161   |  61   |   q	     |					  |
     |	162   |  62   |   r	     |					  |
     |	163   |  63   |   s	     |					  |
     |	164   |  64   |   t	     |					  |
     |	165   |  65   |   u	     |					  |
     |	166   |  66   |   v	     |					  |
     |	167   |  67   |   w	     |					  |
     |	170   |  70   |   x	     |					  |
     |	171   |  71   |   Y	     |					  |
     |	172   |  72   |   z	     |					  |
     |	173   |  73   |   {	     |					  |
     |	174   |  74   |   |	     |					  |
     |	175   |  75   |   }	     |					  |
     |	176   |  76   |   ~	     | Tilde				  |
     |	177   |  77   |   DEL	     | RUBOUT				  |
     ----------------------------------------------------------------------











				      A-4






				  APPENDIX B

			   MACREL MAINTENANCE PROCEDURES



     This  appendix  provides  you  with  some   general   guidelines   for
     maintenance and for diagnosing problems with MACREL.

     One general technique is to  use  the  DUMP:  handler  as  the  binary
     output  file  during  assembly. This allows you to obtain a listing of
     the assembled binary. The OS/8 System Reference Manual  provides  more
     information about DUMP:.

     Another useful diagnostic tool is to obtain a memory dump of the parts
     of  MACREL  that are currently in memory. This procedure is especially
     useful when checking the integrity of the symbol table.  By  examining
     the  symbol  table  and  the bucket pointers you can easily follow the
     chunk chains through memory, since each chunk begins with a pointer to
     the next chunk.

     To do this, restart OS/8 at location 7600 and save memory as follows:

	  .SAVE SYS CORDMP 16000-17577,20000-27577,nnnnn-mmmmm,...  <RET>

     where:

	  mmmmm-nnnnn	      represents other areas  of  memory  that  you
			      wish to dump

     You can print the CORDMP.SV file on the line printer,  using  PIP  and
     the DUMP: handler.

     If MACREL halts, it is important to determine which  overlays  are  in
     memory.  You  can  do  this easily by examining the first word in each
     overlay region (See Table E-1).   Bits  7  through  11  of  this  word
     specify  the  number of the overlay that is currently resident in that
     region.

     You can determine the line currently being processed by examining  the
     input buffer located LINBUF (MACIO).

     You  can  determine  the  input  coroutine  currently  being  used  by
     examining NEXTCHAR (MAC24).








				      B-1






				  APPENDIX C

		       SUMMARY OF MACREL'S MAJOR MODULES



     Name     Overlay			     Description


     AINIT    FIN5	      Sets the initial values at the start of  each
   			      pass.

     ASEMBL   MAC24	      Controls the parsing of input lines.

     ASEMLV   MAC24	      Sends the currently  assembled  statement  to
			      OUTDATA.

     BACKL    EXPOVR	      Processes backslashes (\) and forward slashes
			      (/).

     BACKSL   MAC24	      Processes a backslash (\) in a symbol.

     BACKUP   MAC24	      Moves the line buffer  pointer  back  to  the
			      previous character.

     BINFO    OVRQ	      Sends  the  macrel  fish  caricature  to  the
			      listing file.

     BLKLET   OVRQ	      Sets up the block letter printer.

     BPUT     MAC2	      Stores the PC in the current page.

     BPUTX    PAS2	      Sends the binary word and flag field  to  the
			      binary  buffer  and starts a new flag word if
			      necessary.

     BRAN     MAC24	      Performs a branch-on-condition.

     BRANCH   MAC24	      Performs a branch-on-matching-character.

     CALLIT   MAC24	      Implements cross-field subroutine calls.

     CHKFUL   PAS2	      Sends the binary buffer, when  full,  to  the
			      binary file.

     CHKKBD   MACERR	      Checks to see if a CTRL/C, CTRL/S, CTRL/O, E,
			      F, or L was typed.

						   (continued on next page)



				      C-1
			SUMMARY OF MACREL'S MAJOR MODULES


     Name     Overlay			     Description


     CMNMOV   MACLIT	      Obtains the next literal  value  from  either
			      the  Current Page Literal Table or the Page 0
			      Literal Table.

     CNVADR   MAC24	      Converts  a  15-bit  pointer   into   a   CDF
			      instruction and a 12-bit address.

     CONV     MACIO	      Converts  a  15-bit  pointer   into   a   CDF
			      instruction and a 12-bit address.

     CORE     MACINI	      Determines the real physical memory size.

     CPYTOC   FIN5	      Copies the table-of-contents to  the  listing
			      file.

     CREATE   MACRO	      Fetches a new chunk from FREESPACE to be used
			      for macro space.

     CREF     MAC24	      Sends a symbol name and its  line  number  to
			      the cross-reference file.

     CREFX    PAS2	      Creates a cross-reference listing file.

     CRLF     MAC30	      Sends a RETURN and LF to the listing file.

     CRLFF    MACERR	      Sends a RETURN and LF to OUTDEY.

     CTRLC    MAC24	      Implements CTRL/C exit to the OS/8 Monitor.

     DATE     MACINI	      Obtains the current OS/8 system date.

     DELETE   MACIO	      Deletes characters from macro space.

     DELITE   MACRO	      Deletes  the  old   macro   definition   upon
			      redefinition.

     DIGIT    MAC24	      Determines if a character is a digit.

     DPRINT   MAC30	      Sends a decimal number to NPRINT.

     ENTER    MAC24	      Enters a symbol into the symbol table.

     EOS      MAC24	      Determines if  the  current  character  is  a
			      statement delimiter.

     EQL      MAC24	      Implements   the   direct   assignment    (=)
			      operator.

     ERROR    MAC24	      Processes calls to print error messages.

						   (continued on next page)

				      C-2
			SUMMARY OF MACREL'S MAJOR MODULES


     Name     Overlay			     Description


     EXPOVR   OVRZ	      Implements the uparrow  (^),  backslash  (\),
			      single  quote ('), and percentage (%) symbols
			      in expressions.

     EXPSTK   MACIO	      Expression stack.

     FIN2     FIN2	      Performs  end  of  passes   1,   2,   and   4
			      processing.

     FIN3     FIN3	      Prepares the symbol table for printing.

     FINI     MAC24	      Loads  overlay  22  (OVRR)  for   end-of-pass
			      processing.

     FINMS    MACRO	      Terminates storage into macro space.


     FINIO    MACIO	      Initializes the binary output  file  for  the
			      Loader Symbol Dictionary (LSD).

     FSCHEK   MAC24	      Checks   the   current   value   for   .FSECT
			      relocatability.

     GENUN    MACLIT	      Creates Page 0 literals for unnamed .ASECTs.

     GET      MAC24	      Obtains a character from the line buffer.

     GETCHR   MAC24	      Obtains a character and its  type  code  from
			      the line buffer.

     GETEX    MAC24	      Parses a single expression.

     GETFLG   PAS2	      Starts a new flag word.

     GETLSD   MAC24	      Obtains the LSD number of a specified entry.

     GETKAR   MAC24	      Obtains a character from the line buffer.

     GETOS    MACIO	      Gets characters from the stream input buffer.

     GETSYM   MAC24	      Obtains a symbol table entry from the  symbol
			      table.

     GLOB2    OVRE	      Processes     globals     (general     global
			      processing).

     HGHSCT   MAC24	      Obtains the highest address used by a program
			      section.

						   (continued on next page)


				      C-3
			SUMMARY OF MACREL'S MAJOR MODULES


     IDIV     EXPOVR	      Performs division.

     IGNORE   MAC24	      Ignores the current  input  line  up  to  the
			      end-of-line.

     IMUL     EXPOVR	      Performs multiplication.

     INITMP   MACRO	      Initializes the macro processor at the  start
			      of each pass.

     INITMS   MACRO	      Initializes a new chunk for storage.

     IOINIT   MACIO	      Initializes the input  coroutines  and  their
			      switching mechanism.

     IONIT2   MACIO	      Initializes variables to  prepare  for  first
			      input file.

     KLU4     MAC24	      Obtains the lowest address used by an .ASECT.

     KLU10    MACLIT	      Patch to PURGEL.

     KRFCHN   OVRT	      Chains to KREF after assembly is complete.

     LETTER   MAC24	      Determines if  the  current  character  is  a
			      letter or a symbol.

     LIMSET   MACINI	      Sets up the memory limit table.

     LIST     MAC30	      Sends the entire line to LISTER.

     LISTER   MAC3R	      Sends characters to the listing file.

     LOAD     MAC24	      Loads MACREL's internal overlays.

     LOCPOP   MACIO	      Removes (pops) coroutine local variables from
			      the stream stack.

     LOCPSH   MACIO	      Places (pushes) coroutine local variables on
			      the stream stack.

     LOOKU    MACIO	      Searches a device for a file.

     LOOKUP   MAC24	      Searches the symbol table for symbol.

     LOOP     MAC24	      Controls the entire assembly process (main
			      loop routine).

     LNKCHN   OVRT	      Chains to LINK and KREF (if requested)  after
			      assembly is complete.

     LPATCH   MAC24

						   (continued on next page)

				      C-4
			SUMMARY OF MACREL'S MAJOR MODULES


     LSDINI   FIN2	      Sends the Loader Symbol Dictionary preface to
			      the binary file.

     LSDOUT   FIN2	      Sends the Loader Symbol Dictionary  entry  to
			      the binary file.

     LSTRET   MACIO	      Obtains a character to be sent to the listing
			      file.

     MACTBL   (MACORG)	      Character branch table.

     MATCH    MACRO	      Checks the current symbol for a match against
			      a keyword list.

     MC	      MACMAC	      Implements a .MACRO call.

     MGET     MACIO	      Obtains text from .MACRO and .MACRO  argument
			      space.

     MORCRF   PAS2	      Sends   cross-reference   information   about
			      literals to the cross-reference file (KREF).

     MS	      MACRO	      Stores a word  in  the  current  location  in
			      macro space.

     NEWPAG   MAC3R	      Sets up a new listing page for printing.

     NEX      MAC24	      Controls start of all passes.

     NEXTCHAR MAC24	      Obtains next  character  from  current  input
			      stream

     NEXTT    FIN0	      Performs beginning of pass initialization.

     NUMLCL   MAC24	      Processes numeric local labels.

     OFETCH   MACOPN	      Loads the output device handler.
	      (MACIO)

     OFIX     MACIO 	      Refetches a device handler for OGET.

     OGET     MACIO	      Gets  a  character  from  the  stream   input
			      buffer.

     ONCE     MACINI	      Initializes  the  assembler  during   initial
			      startup.

     OPEN     MACOPN	      Opens an output file.

     OPEN1    FIN0	      Opens the table-of-contents file (pass 1).

     OPEN2    FIN0	      Opens the binary output file (pass 2).

						   (continued on next page)

				      C-5
			SUMMARY OF MACREL'S MAJOR MODULES


     OPEN3    FIN0	      Opens the listing file (pass 3).

     OPEN4    FIN0	      Opens the cross-reference listing file  (pass
			      4).

     OPENTC   MACOPN	      Sets up the listing file to receive the table
			      of contents.

     OPRINT   MAC30	      Sends an octal number to NPRINT.

     ORIG     MAC2	      Sets up the flag word and sends the PC to the
			      binary output file.

     ORIGI    MACORG	      Sets the current location  (program)  counter
			      (PC)

     OUT      MAC3R	      Sends a line to the listing file.

     OUTBLK   OVRQ	      Sends the block letter heading to the listing
			      file.

     OUTDATA  MAC24	      Sends binary data to the binary file.

     OUTDEY   MACERR	      Contains  the  name  of  the  current  output
			      device (either PR or LPUT).

     OUTLST   MACIO	      Packs the output buffer with characters.

     OVRLIN   MAC3R	      Allows listing file page overflow.

     PART2    MACMAC	      Stores the body of a macro in macro space.

     PASS3    MAC3R	      Tests if this is pass 3.

     PARSYM   MAC24	      Parses a symbol.

     POP      MAC24	      Removes a character from expression stack.

     PR	      MACERR	      Sends a character to the BATCH log device  if
			      CTRL/O  is  not  in  effect.  Also checks for
			      CTRL/O, CTRL/C, CTRL/S, and the E, F,  and  L
			      options.

     PR2      MACERR	      Sends two 6-bit ASCII characters to PR.

     PR6      MACERR	      Prints one 6-bit ASCII character using PR.

     PR6A     MACERR	      Prints a 6-bit ASCII character on the  output
			      device.

     PR12     MACERR	      Prints one 12-bit number as 4  octal  digits,
			      using PR.

						   (continued on next page)

				      C-6
			SUMMARY OF MACREL'S MAJOR MODULES


     PRCHR    MACERR	      Prints  single  characters  on   the   output
			      device.

     PREFIN   OVRR	      Performs pre-end-of-pass tasks.

     PREFORM  MACINI	      Formats  unused   memory   into   chunks   of
			      FREESPACE.

     PRINTY   MAC30	      Sends PC, binary data, and its qualifiers  to
			      the print routine.

     PRLINO   MAC2	      Prints  the  line  number  on  the   assembly
			      listing.

     PRGLIT   MAC24	      Uses PURG to load  MACLIT  overlay  to  purge
			      current page literals.

     PRGSPL   MACLIT	      Purges the Page 0 literals  in   an   unnamed
			      .ASECT.

     PRN      FIN3	      Sends a symbol name to the listing file.

     PRNAM    MACERR	      Sends  a  6-character  name  to  the   output
			      device.

     PRNBIN   MAC30	      Sends binary code to listing file.

     PRNDSH   MAC30	      Sends five dashes (-) to listing file.

     PRNT2    FIN3	      Sends two  packed  6-bit  characters  to  the
			      listing file.

     PRNT6    FIN3	      Sends one  6-bit  character  to  the  listing
			      file.

     PRZLIT   MAC24	      Uses PURG to load  MACLIT  overlay  to  purge
			      Page 0 literals.

     PUNBIT   MAC2	      Sends a binary word and its flag field to the
			      binary output file.

     PUNY     MAC2	      Determines whether this is pass 2 and whether
			      binary output is enabled.

     PURGEL   MACLIT	      Purges literals from a literal pool.

     PUSH     MAC24	      Saves a character on the expression stack.

     PUTB     MAC2	      Calls PUTBT if this is pass 2 and  if  binary
			      output is enabled.

						   (continued on next page)



				      C-7
			SUMMARY OF MACREL'S MAJOR MODULES


     PUTBIT   MAC2	      Sends a binary entry without a flag field  to
			      the binary file.

     PUTBN    PAS2	      Sends a binary word and its flag field to the
			      binary buffer.

     PUTBT    PAS2	      Sends a binary word to the binary buffer.

     PUTBUF   MACIO	      Sends  a  bufferful  of  characters  to   the
			      listing device.

     PUTLC    MAC2	      Sends a loader code to  the  binary  file  if
			      this is pass 2 and binary output is enabled.

     PUTSYM   MAC24	      Inserts symbol  table  information  into  the
			      symbol table.

     PUXBIN   MAC2	      Sends a binary word and its flag field to the
			      binary output file.

     READLN   MAC24	      Reads a line of text from the current  stream
			      into the input buffer.

     READOS   MACIO	      Reads characters from the input file into the
			      input buffer.

     REIT     FIN5	      Completes a return after  opening  an  output
			      file.

     RENEW    MACRO	      Resets the character scan to the beginning of
			      the line.

     RGET     MACIO	      Obtains text from .REPEAT storage space.

     ROTL6    MAC24	      Performs a six-bit, left-shift operation.

     SCAN     MAC24	      Skips over spaces and tabs.

     SETIT    MAC24	      Creates a new  title  or  subtitle  from  the
			      current line.

     SETNAM   MACERR	      Sets up a name to be printed by PRNAM.

     SETT     MAC30	      Sets up a new title from current line.

     SKSEP    MACRO	      Skips past a sequence of spaces and/or tabs.

     SNGLQQ   EXPOVR	      Processes single quotation marks (').

     SPOP     MACIO	      Removes (pops) arguments from any stack.

     SPUSH    MACIO	      Places (pushes) arguments on any stack.

						   (continued on next page)

				      C-8
			SUMMARY OF MACREL'S MAJOR MODULES


     STNAM    MACERR	      Sets up a symbol table name for printing.

     STORMS   MACRO	      Stores the AC in macro space.

     STPRNT   FIN3	      Sends  a  physical  page  of   symbol   table
			      information to the listing file.

     STRSTK   MACIO	      Pushdown stack for input coroutine switching.

     SWBACK   MACIO	      Controls  switching  of  the   input   stream
			      coroutines back to the previous stream.

     SWITCH   MACIO	      Controls  switching  of  the   input   stream
			      coroutines.

     SYMINI   MACINI	      Builds the run-time symbol table.

     TAB      MAC30	      Sends a tab character to the listing file.

     TAGCOL   MAC24	      Processes a tag ending with a colon (:).

     TAGCOM   MAC24	      Processes a tag ending with a comma(,).

     TASKY    OVRC	      Implements the obsolete .TASK directive.

     TP	      MACERR	      Sends a character  (unconditionally)  to  the
			      terminal.

     TPUT     MACERR	      Sends a character  (unconditionally)  to  the
			      BATCH log device.

     TSTEOL   MACRO	      Tests an end-of-line character.

     TSTMAC   MAC24	      Checks whether a symbol is a macro call.

     TSTQUOTE MACRO	      Tests for a double quotation mark (").

     TSTTERM  MACRO	      Tests for a terminator (slash, semicolon,  or
			      end-of-line).

     TYPE     MACERR	      Prints a 6-bit character or RETURN/LF (if NUL
			      character) on OUTDEY.

     TYPERR   MACERR	      Sends an error message to the error log  (TTY
			      or BATCH log file.).

     UNNAM    MAC2	      Creates and names an unnamed .ASECT.

     UPAROQ   EXPOVR	      Processes the temporary radix operators  (^B,
			      ^D, and ^0).

     USRSTK   MACIO	      .PUSH and .POP directive stack (OVRU).

						   (continued on next page)

				      C-9
			SUMMARY OF MACREL'S MAJOR MODULES


     XPRINT   FIN3	      Sends a symbol's binary value to the  listing
			      file.

     ZGET     MACIO	      Sends CTRL/Zs to the input stream.

     ZINIT    MACIO	      Initializes the .MACRO processor.

     ZL	      MACLIT	      Dumps the Page 0 literal pool.

     ZLIT     MACLIT	      Purges the Page 0 literal pool.

     ZPAD     FIN2	      Pads the binary buffer with CTRL/Zs.

     ZSECTG   MACLIT	      Creates Page 0 literals.

     $ASECT   OVRD	      Implements the .ASECT directive.

     $CDF     MACEXP	      Implements the CDF special operator.

     $CHAIN   OVRE	      Implements the .CHAIN directive.

     $CIF     MACEXP	      Implements the CIF special operator.

     $DECIMA  OVRC	      Implements the DECIMAL directive.

     $DEVICE  OVRC	      Implements the DEVICE directive.

     $DISABL  OVRC	      Implements the .DISABLE directive.

     $DOT     MACEXP	      Implements the period (.) special operator.

     $DSECT   OVRD	      Implements the .DSECT directive.

     $EDF     MACEXP	      Implements the EDF special operator.

     $EJECT   OVRU	      Implements the EJECT directive.

     $ENABLE  OVRC	      Implements the .ENABLE directive.

     $ENPUNC  OVRR	      Implements the ENPUNCH directive.

     $ENTRY   OVRE	      Implements the .ENTRY directive.

     $EXPNG   OVRS	      Implements the EXPUNGE directive.

     $EXTERN  OVRE	      Implements the .EXTERNAL directive.

     $FIELD   OVRT	      Implements the FIELD directive.

     $FILENA  OVRC	      Implements the FILENAME directive.

     $FIXMRI  MAC24	      Implements the FIXMRI directive.

						   (continued on next page)

				     C-10
			SUMMARY OF MACREL'S MAJOR MODULES


     $FIXTAB  OVRS	      Implements the FIXTAB directive.

     $FLD     MACEXP	      Implements the .FLD special operator.

     $FSECT   OVRD	      Implements the .FSECT directive.

     $GLOBAL  OVRE	      Implements the .GLOBAL directive.

     $I	      MACEXP	      Implements the I special operator.

     $IF      OVRB	      Implements IF directive.

     $IFDEF   OVRB	      Implements the IFDEF directive.

     $IFNDEF  OVRB	      Implements the IFNDEF directive.

     $IFNZRO  OVRB	      Implements the IFNZRO directive.

     $IFZERO  OVRB	      Implements the IFZERO directive.

     $INCLUD  OVRE	      Implements the .INCLUDE directive.

     $JSW     OVRR	      Implements the .JSW directive.

     $LEVEL   MACEXP	      Implements the LEVEL keyword.

     $LIST    OVRR	      Implements the .LIST directive.

     $MACRO   MACMAC	      Processes the header of a .MACRO definition.

     $MEXIT   MACMAC	      Implements the .MEXIT directive.

     $NARGS   MACMAC	      Implements the .NARGS special operator.

     $NCHARS  MACEXP	      Implements the .NCHARS special operator.

     $NOLIST  OVRR	      Implements the .NOLIST directive.

     $NOPUNC  OVRR	      Implements the NOPUNCH directive.

     $OCTAL   OVRC	      Implements the OCTAL directive.

     $PAGE    OVRA	      Implements the PAGE directive.

     $PAUSE   MAC24	      Ignores PAL8 PAUSE directives.

     $POP     OVRU	      Implements the .POP directive.

     $PUSH    OVRU	      Implements the .PUSH directive.

     $RADIX   OVRC	      Implements the RADIX directive.

						   (continued on next page)


				     C-11
			SUMMARY OF MACREL'S MAJOR MODULES


     $RELOC   OVRU	      Implements the RELOC directive.

     $REPT    MACMAC	      Implements the the .REPT directive.

     $RSECT   OVRD	      Implements the .RSECT directive.

     $SBTTL   OVRU	      Implements the .SBTTL directive.

     $SECREF  OVRE	      Implements the .SECREF directive.

     $SECT    OVRD	      Implements the .SECT directive.

     $START   OVRR	      Implements the .START directive.

     $TEXT    OVRA	      Implements the TEXT directive.

     $TITLE   OVRU	      Implements the .TITLE directive.

     $VERSIO  OVRR	      Implements the .VERSION directive.

     $XEDF    MACEXP	      Implements the XEDF special operator.

     $XLIST   OVRR	      Implements the XLIST directive.

     $XSECT   OVRD	      Implements the .XSECT directive.

     $Z	      MACEXP	      Implements the Z special operator.

     $ZBLOCK  OVRA	      Implements the ZBLOCK directive.

     $ZSECT   OVRD	      Implements the .ZSECT directive.

     $ZTRNA   OVRE	      Implements the .ETERNAL directive.






















				     C-12






				  APPENDIX D

	 BATCH FILES FOR ASSEMBLING AND LINKING MACREL, LINK, AND KREF



     This appendix shows you the basic sequence of steps necessary to build
     the MACREL, LINK, and KREF source modules into executable files.

     It consists of a listing example of an OS/8 BATCH command file (Figure
     D-1)  that  assembles  and links MACREL, LINK, and KREF. The file also
     includes previously unpublished binary patches that update  MACREL  to
     version  V2C  and  LINK  to  version  V2AG.  You will find more binary
     patches published in the issues of the  Digital  Software  News  (DSN)
     beginning June/July 1979.

     The output files that result from  this  process  are  the  MACREL.SV,
     LINK.SV, and KREF,SV files and the LINK map listings for MACREL, LINK,
     and KREF. If you wish to obtain assembly  and  cross-reference  (KREF)
     listings,  you  must  modify  each command line that invokes MACREL to
     include the  appropriate  command  string  options  and  listing  file
     specification  (refer  to the MACREL/LINK User's Manual). For example,				   _________________________
     the following command lines send the listing  for  PAS2  to  the  line
     printer.

	  .R MACREL
	  *DEV:PAS2,LPT:<DEV:PAS2/B/C/K

     The  listing  will  have   a   block-letter   heading   (/B)   and   a
     cross-reference  listing  that  contains local symbols (/C and /K). If
     you do not print the listing directly on the line printer (LPT:),  you
     should  determine  whether  there  is  sufficient space on your output
     device to contain all the listing files.

     The batch file operates with the following conditions:

	  o  You must run this batch file under the control of the OS/8 V3D
	     Combined Kit Software.

	  o  This batch file  and  MACREL.SV  must  reside  on  the  device
	     assigned to SYS:

	  o  The global symbol definition files MGLOB.MA and LNKMAN.MA must
	     reside on the device assigned to DSK:

	  o  The input/output device for all other files is RLOB: (see  the
	     ASSIGN statement at the beginning of the file).





				      D-1
	 BATCH PILES FOR ASSEMBLING AND LINKING MACREL, LINK, AND KREF


	   Figure D-1 BATCH File for Building MACREL, LINK, and KREF

     /*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
     /
     $JOB MACREL/LINK BATCH FILE
     /
     .ASSIGN RL0B DEV
     /
     /make sure the global definition files are on DSK:
     /COPY DSK:<DEV:MGLOB.MA,LNKMAN.MA
     /
     /
     /				    *-*-*-*-*-*-*-*
     /				    ASSEMBLE HACREL
     /				    *-*-*-*-*-*-*-*
     /
     .R MACREL
     *DEV:PAS2<DEV:PAS2
     .R MACREL
     *DEV:OVRS<DEV:OVRS
     .R MACREL
     *DEV:OVRE<DEV:OVRE
     .R MACREL
     *DEV:MACEXP<DEV:MACEXP
     .R MACREL
     *DEV:EXPOVR<DEV:EXPOVR
     .R MACREL
     *DEV:FIN0<DEV:FIN0
     .R MACREL
     *DEV:OVRU<DEV:OVRU
     .R MACREL
     *DEV:OVRT<DEV:OVRT
     .R MACREL
     *DEV:OVRB<DEV:OVRB
     .R MACREL
     *DEV:MAC3R<DEV:MAC3R
     .R MACREL
     *DEV:OVRD<DEV:OVRD
     .R MACREL
     *DEV:OVRC<DEV:OVRC
     .R MACREL
     *DEV:MACRO<DEV:MACRO
     .R MACREL
     *DEV:MACOPN<DEV:MACOPN
     .R MACREL
     *DEV:MACMAC<DEV:MACMAC
     .R MACREL
     *DEV:MACRTH<DEV:MACRTH
     .R MACREL
     *DEV:MAC2<DEV:MAC2
     .R MACREL
     *DEV:MACORG<DEV:MACORG
     .R MACREL
     *DEV:MACLIT<DEV:MACLIT

				      D-2
	 BATCH PILES FOR ASSEMBLING AND LINKING MACREL, LINK, AND KREF


     .R MACREL
     *DEV:OVRA<DEV:OVRA
     .R MACREL
     *DEV:MAC30<DEV:MAC30
     .R MACREL
     *DEV:OVRR<DEV:OVRR
     .R MACREL
     *DEV:MACTBL<DEV:MACTBL
     .R MACREL
     *DEV:FIN3<DEV:FIN3
     .R MACREL
     *DEV:MACINI<DEV:MACINI
     .R MACREL
     *DEV:MACERR<DEV:MACERR
     .R MACREL
     *DEV:OVRQ<DEV:OVRQ
     .R MACREL
     *DEV:MAC24<DEV:MAC24
     .R MACREL
     *DEV:MACIO<DEV:MACIO
     .R MACREL
     *DEV:FIN2<DEV:FIN2
     .R MACREL
     *DEV:MACLOD<DEV:MACLOD
     /
     /
     /				    *-*-*-*-*-*-*
     /				    ASSEMBLE LINK
     /				    *-*-*-*-*-*-*
     .R MACREL
     *DEV:LNKCAL<DEV:LNKCAL
     .R MACREL
     *DEV:LNKLSD<DEV:LNKLSD
     .R MACREL
     *DEV:LNKCD<DEV:LNKCD
     .R MACREL
     *DEV:LNKALL<DEV:LNKALL
     .R MACREL
     *DEV:LNKMAP<DEV:LNKMAP
     .R MACREL
     *DEV:LNKBN1<DEV:LNKBN1
     .R MACREL
     *DEV:LNKBN2<DEV:LNKBN2
     .R MACREL
     *DEV:LNKMSG<DEV:LNKMSG
     /
     /				    *-*-*-*-*-*-*
     /				    ASSEMBLE KREF
     /				    *-*-*-*-*-*-*
     /
     .R MACREL
     *DEV:KREF<DEV:KREF
     /
     /

				      D-3
	 BATCH PILES FOR ASSEMBLING AND LINKING MACREL, LINK, AND KREF


     /				    *-*-*-*-*-*
     /				    LINK MACREL
     /				    *-*-*-*-*-*
     /
     .R LINK
     *DEV:MACREL,LPT:<DEV:MACERR,MACINI,FIN3,PAS2,OVRS/K=6
     *DEV:OVRE,MACEXP,EXPOVR,MACLOD/W=200
     *DEV:FIN0,OVRU,OVRT,OVRQ,OVRB,MAC3R,MAC30
     *DEV:OVRD,OVRC,MACRO,MACOPN,MACRTH,MAC2,MACORG,MACLIT
     *DEV:FIN2,OVRA,MAC24,OVRR,MACIO,MACMAC,MACTBL$
     /
     /
     /				    *-*-*-*-*
     /				    LINK LINK
     /				    *-*-*-*-*
     .R LINK
     *DEV:LINK,LPT:<DEV:LNKCAL/O
     *DEV:LNKCD/C
     *DEV:LNKLSD/C
     *DEV:LNKALL/C
     *DEV:LNKMAP/C
     *DEV:LNKBN1/F/C
     *DEV:LNKBN2/C
     *DEV:LNKMSG$
     /
     /
     /				    *-*-*-*-*
     /				    LINK KREF
     /				    *-*-*-*-*
     .R LINK
     *DEV:KREF,LPT:<DEV:KREF$
     /
     /
     /		     *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
     /		     Make a patched version of FUTIL that will
     /		     accept block offset (B+n) commands.
     /		     *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
     .R FOTP
     *XFUTIL.SV<FUTIL.SV
     .R FUTIL
     FILE XFUTIL.SV
     SET MODE SAVE
     SHOW CCB
     1517/ 5720;5761;4531
     3321/ 7100;1360;7006;7006
     5533/ 1077
     5761/ 3023;1023;113;5765;1521
     WRITE
     EXIT
     /
     /	




				      D-4
	 BATCH PILES FOR ASSEMBLING AND LINKING MACREL, LINK, AND KREF


     /		     *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
     /		     Patch MACREL to create MACREL V2C from V2A
     /		     don't forget to set 200's bit of word 3 in
     /		     the memory control block (CCB).
     /		     *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
     /
     .R XFUTIL
     SET DEV DEV
     FILE MACREL.SV
     SET MODE SAVE
     SHOW CCB
     COMMENT -------------Fix bug with COS text packing
     32155/ 7440;1362;126;5754
     32140/ 4354;7000
     32145/ 4354;7000
     COMMENT -------------Fix hang on .ZBLOCK to complex relocatable 
     COMMENT -------------expression
     32064/ 5245
     COMMENT -------------Allow links in .FSECTs
     20651/ 5334
     20734/ 1647;3321;2247;1647;3350;2247;1765;5252;3721;3750;6202;5647
     20673/ 3721
     20701/ 3721
     20706/ 1721
     20711/ 1721
     20717/ 3750;5020
     20020/ 7240;1425;7540;5426;5427;41;746;744
     4122/ 6222;4727;3757;3760;5344;647;6222;4727;53;54;5735;4415
     4413/ 5614;4130
     COMMENT -------------Fix 12k background system
     2045/ 5307
     2107/ 1006;7700;5247;5257
     COMMENT -------------Insert additiona1 patches starting here
     COMMENT -------------Change patch level to C
     13136/ 103
     COMMENT -------------End of MACREL patches
     WRITE
     SET MODE NORMAL
     /
     /		     *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
     /		     Patch LINK to create LINK V2AG from V2a
     /		     *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
     /
     FILE LINK.SV
     SH CCB
     (B+1).111/ 0107
     (B+1).226/ 7420;5625;1234;1026;5633;1155;0200
     (B+3).147/ 4767
     (B+3).154/ 2366;3026
     (B+3).167/ 0225
     (B+16).46/ 5251
     (B+16).51/ 1057;0257;7640;4767;7200;5522;0040
     (B+24).250/ 3010
     (B+24).326/ 4763

				      D-5
	 BATCH PILES FOR ASSEMBLING AND LINKING MACREL, LINK, AND KREF


     (B+24).335/ 1010
     (B+24).355/ 5762
     (B+24).362/ 3330;3320
     (B+25).312/ 2045;1445;2311;7450;7100;5711
     (B+25).321/ 4727;4726;5720;5725;3044;4216;2535
     (B+25).330/ 1012;7001;3055;5734;2430
     (B+27).252/ 7200
     (B+32).357/ 4760;3311
     (B+42).106/ 7450;5777;3041;5705
     (B+42).265/ 4755
     (B+42).355/ 2505
     WRITE
     EXIT
     /				*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
     /				MACREL/LINK ASSENBLY AND LINKING COMPLETE
     /				*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
     $END






































				      D-6






				  APPENDIX E

		     MEMORY UTILIZATION AND MODULE SUMMARY



				   Table E-1
			   MACREL Memory Utilization

     ----------------------------------------------------------------------
     | Locations   | Module | Program |	       Comments			  |
     | 		   |	    | Section |					  |
     |-------------|--------|---------|-----------------------------------|
     |		   |	    |	      |					  |
     | 00000-00122 | MAC24  | MAIN7   |					  |
     |		   |	    |	      |					  |
     | 00123-00173 | all    | LITS    | Literals defined in the MGLOB.MA  |
     | 		   |	    |	      | file				  |
     |		   |	    |	      |					  |
     | 00200-00777 | MAC24  | MAIN    |					  |
     |		   |	    |	      |					  |
     | 01000-01177 | MAC3R  | MAC3R   |					  |
     |		   |	    |	      |					  |
     | 01200-01377 | MAC2   | MAC2    |					  |
     |		   |	    |	      |					  |
     | 01400-01777 | MACINI | MACINI  | Pass-specific Overlay Area	  |
     |		   |	    |	      |					  |
     | 02000-02377 | MACINI | MACINI  | Once-only code and Directives	  |
     | 	   	   |	    |	      |	Overlay Area			  |
     |		   |	    |	      |					  |
     | 02400-02777 | MACINI | MACINI  | Once-only code and Auxiliary	  |
     | 		   |	    |	      |	Overlay Area			  |
     |		   |	    |	      |					  |
     | 03000-04577 | MACEXP | MACEXP  |					  |
     |		   |	    |	      |					  |
     | 04600-05577 | MAC24  | MAIN.3  |					  |
     |		   |	    |	      |					  |
     | 05600-05777 | MACRO  | MACRO   |					  |
     |		   |	    |	      |					  |
     | 06000-06377 | MAC24  | MAIN.4  |					  |
     |		   |	    |	      |					  |
     | 06400-06777 | MACINI | MACIN2  | Once-only code, Extremities	  |
     | 		   |	    |	      | Overlay Area Input device handler |
     |		   |	    |	      | area				  |
     |		   |	    |	      |					  |
     | 07000-07177 | MAC24  | MAIN.5  |					  |
     |		   |	    |	      |					  |
     | 07200-07577 | MACINI | MACIN3  | Output device handler		  |
     ----------------------------------------------------------------------
						 (continued on next page)


				      E-1
		     MEMORY UTILIZATION AND MODULE SUMMARY


			       Table E-1 (Cont.)
			   MACREL Memory Utilization

     ----------------------------------------------------------------------
     | Locations   | Module | Program |	       Comments			  |
     | 		   |	    | Section |					  |
     |-------------|--------|---------|-----------------------------------|
     |		   |	    |	      |					  |
     | 07677-07777 | ------ | ------  | OS/8 Monitor			  |
     |		   |	    |	      |					  |
     | 10000-10017 | ------ | ------  | Unused				  |
     |		   |	    |	      |					  |
     | 10020-10055 | MACIO  | MACIO7  |					  |
     |		   |	    |	      |					  |
     | 10056-10060 | MACIO  | $MACIO2 | .ZSECT created by MACIO2 for Page |
     | 		   |	    |	      | 0 literals			  |
     |		   |	    |	      |					  |
     | 10061-10100 | MACIO  | $MACIO5 | .ZSECT created by MACIO2 for Page |
     | 		   |	    |	      | 0 literals			  |
     |		   |	    |	      |					  |
     | 10101-10107 | MACIO  | $MACIO  | .ZSECT created by MACIO2 for Page |
     | 		   |	    |	      | 0 literals			  |
     |		   |	    |	      |					  |
     | 10110-10177 | ------ | ------  | Unused Page 0 locations		  |
     |		   |	    |	      |					  |
     | 10200-10577 | MACIO  | MACIO   |					  |
     |		   |	    |	      |					  |
     | 10600-10777 | MACTBL | MACTAB  |					  |
     |		   |	    |	      |					  |
     | 11000-11177 | MACRO  | AT      |					  |
     |		   |	    |	      |					  |
     | 11200-11777 | MACIO  | MACIO2  |					  |
     |		   |	    |	      |					  |
     | 12000-12777 | MACIO  | MACIO3  | Input buffer			  |
     |		   |	    |	      |					  |
     | 13000-13277 | MAC24  | MAIN.6  | Heading and title buffers and	  |
     |		   |	    |	      |	once-only code			  |
     |		   |	    |	      |					  |
     | 13300-13377 | MAC24  | MAIN.6  |					  |
     |		   |	    |	      |					  |
     | 13400-13777 | MACIO  | MACIO4  | Output buffer			  |
     |		   |	    |	      |					  |
     | 14000-14177 | MACIO  | MACIO4  | Line buffer			  |
     |		   |	    |	      |					  |
     | 14200-14377 | MACIO  | MACIO4  | Current page literal pool	  |
     |		   |	    |	      |					  |
     | 14400-14577 | MACIO  | MACIO4  | Current field, Page 0 literal pool|
     |		   |	    |	      |					  |
     | 14600-15377 | MACIO  | MACIO5  |					  |
     |		   |	    |	      |					  |
     | 15400-17577 | MACINI | SYMTAB  | Initial symbol table		  |
     |		   |	    |	      |					  |
     ----------------------------------------------------------------------
						 (continued on next page)

				      E-2
		     MEMORY UTILIZATION AND MODULE SUMMARY


			       Table E-1 (Cont.)
			   MACREL Memory Utilization

     ----------------------------------------------------------------------
     | Locations   | Module | Program |	       Comments			  |
     | 		   |	    | Section |					  |
     |-------------|--------|---------|-----------------------------------|
     |		   |	    |	      |					  |
     | 17600-17777 | ------ | ------- | OS/8 Monitor			  |
     |		   |	    |	      |					  |
     | 20000-20177 | ------ | ------- | Patch space			  |
     |		   |	    |	      |					  |
     | 20200-20377 | MACLOD | MACLOD  |					  |
     |		   |	    |	      |					  |
     | 20400-20577 | MAC2   | KLUDG2  |					  |
     |		   |	    |	      |					  |
     | 20600-20777 | MACLIT | KLUDG1  | Remainder of MACLIT is in an	  |
     |		   |	    |	      | overlay				  |
     |		   |	    |	      |					  |
     | 21000-21177 | MAC24  | KLUDG4  |					  |
     |		   \							  |
     | 21200-27767  |							  |
     |		    |							  |
     | 30000-37767  |							  |
     |		    |							  |
     | 40000-47767  |							  |
     |		     >  FREESPACE (see note below)			  |
     | 50000-57767  |							  |
     |		    |							  |
     | 60000-67767  |							  |
     |		    |							  |
     | 70000-77767  |							  |
     |		   /							  |
     ---------------------------------------------------------------------|


				     NOTE

		   1.  If OS/8 BATCH is running and  the  Z
		   option   is   not  specified,  locations
		   higher than  5000  in  the  field  where
		   BATCH resides will not be used.

		   2.  If the system device  handler  is  a
		   2-page handler, the high page in field 2
		   will not be used.

		   3.  If there is more than 12K  words  of
		   memory   and   the   Y   option  is  not
		   specified,  locations  lower  than  4000
		   will not be used.
 



				      E-3
		     MEMORY UTILIZATION AND MODULE SUMMARY


		   4.  The   number   of   memory    fields
		   available  to MACREL depends on both the
		   hardware and the software memory size.


				   Table E-2
			  Overlay Module Data Summary

     ----------------------------------------------------------------------
     | 	     |			Overlay					  |
     | Module|------------------------------------------------------------|
     | Name  |Name| No.|Address|    Area    |	   Description		  |
     |-------|----|----|-------|------------|-----------------------------|
     |	     |	  |    |       |	    |				  |
     | OVRA  |OVRA| 01 | 2000  | Directives | PAGE, ZBLOCK, TEXT	  |
     |	     |	  |    |       |	    |				  |
     | OVRB  |OVRB| 02 | 2000  | Directives | .IF, .IFDEF, .IFNDEF,	  |
     | 	     |	  |    |       |	    | .IFZERO, .IFNZRO		  |
     |	     |	  |    |       |	    |				  |
     | OVRC  |OVRC| 03 | 2000  | Directives | Radix control, FILENAME,	  |
     |       |    |    |       |	    | DEVICE, .ENABLE, .DISABLE	  |
     |	     |	  |    |       |	    |				  |
     | OVRD  |OVRD| 04 | 2000  | Directives | .SECT, .ASECT, .RSECT,	  |
     | 	     |	  |    |       |	    | .FSECT, .DSECT, .XSECT,	  |
     |	     |	  |    |       |	    | .ZSECT			  |
     |	     |	  |    |       |	    |				  |
     | OVRE  |OVRE| 05 | 2000  | Directives | .INCLUDE, .CHAIN		  |
     |	     |	  |    |       |	    |				  |
     | MACRTH|OVRF| 06 | 2400  | Auxiliary  | Global arithmetic		  |
     |	     |	  |    |       |	    |				  |
     | MACORG|OVRG| 07 | 2400  | Directives | Origin			  |
     |	     |	  |    |       |	    |				  |
     | FIN0  |OVRH| 10 | 6400  | Extremities| Pass initialization	  |
     |	     |	  |    |       |	    |				  |
     | FIN3  |OVRI| 11 | 2000  | Directives | Symbol table extension	  |
     |	     |	  |    |       |	    |				  |
     | FIN2  |OVRJ| 12 | 6400  | Extremities| Pass 1,2,4 FIN code	  |
     |	     |	  |    |       |	    |				  |
     | FIN3  |OVRK| 13 | 6400  | Extremities| Pass 3 FIN code		  |
     |	     |	  |    |       |	    |				  |
     | FIN2  |OVRL| 14 | 2000  | Directives | Passes 2,4 FIN code	  |
     | 	     |    |    |       |	    | extension			  |
     |	     |	  |    |       |	    |				  |
     | MAC30 |OVRM| 15 | 1400  | Pass-	    | Pass 1 and 3 specific code  |
     | 	     |    |    |       | specific   |				  |
     |	     |	  |    |       |	    |				  |
     | PAS2  |OVRN| 16 | 1400  | Pass-      | Pass 2 _4 specific code	  |
     | 	     |    |    |       | specific   |				  |
     |	     |	  |    |       |	    |				  |
     | ---------- | 17 |  ----------------  | Patch area ------------- 	  |
     |	     |	  |    |       |	    |				  |
     | ---------- | 20 |  ----------------  | Unused ----------------- 	  |
     ----------------------------------------------------------------------
						 (continued on next page)

				      E-4
		     MEMORY UTILIZATION AND MODULE SUMMARY


			       Table E-2 (Cont.)
			  Overlay Module Data Summary

     ----------------------------------------------------------------------
     | 	     |			Overlay					  |
     | Module|------------------------------------------------------------|
     | Name  |Name| No.|Address|    Area    |	   Description		  |
     |-------|----|----|-------|------------|-----------------------------|
     |	     |	  |    |       |	    |				  |
     | OVRQ  |OVRQ| 21 | 2000  | Directives | Block-letter printer	  |
     |	     |	  |    |       |	    |				  |
     | OVRR  |OVRR| 22 | 2000  | Directives | Listing directives pre-FIN  |
     | 	     |    |    |       |	    | overlay .START, .JSW,	  |
     | 	     |    |    |       |	    | .VERSION, NOPUNCH, ENPUNCH  |
     |	     |	  |    |       |	    |				  |
     | OVRS  |OVRS| 23 | 2000  | Directives | FIXTAB, EXPUNGE		  |
     |	     |	  |    |       |	    |				  |
     | OVRT  |OVRT| 24 | 2000  | Directives | Block letter printer, chain |
     | 	     |    |    |       |	    | to LINK			  |
     |	     |	  |    |       |	    |				  |
     | OVRU  |OVRU| 25 | 2000  | Directives | TITLE, SBTITLE, RELOC,	  |
     | 	     |    |    |       |	    | .PUSH, .POP		  |
     |	     |	  |    |       |	    |				  |
     | MACMAC|OVRV| 26 | 2000  | Directives | Macro definition header	  |
     |	     |	  |    |       |	    |				  |
     | MACMAC|OVRW| 27 | 2000  | Directives | Macro definition body .REPT |
     |	     |	  |    |       |	    |				  |
     | MACMAC|OVRX| 30 | 2000  | Directives | Macro invocation		  |
     |	     |	  |    |       |	    |				  |
     | MACLIT|OVRY| 31 | 2400  | Auxiliary  | Literal purger		  |
     |	     |	  |    |       |	    |				  |
     | EXPOVR|OVRZ| 32 | 2400  | Auxiliary  | Implements ^, \, ', %	  |
     | 	     |    |    |       |	    | in expressions		  |
     |	     |	  |    |       |	    |				  |
     | MACOPN| 	  | 33 | 2000  | Directives | FIN0 extension		  |
     |	     |	  |    |       |	    |				  |
     | OVRQ  |    | 34 | 2000  | Auxiliary  | Block-letter data		  |
     |	     |	  |    |       |	    |				  |
     | OVRD  |	  | 35 | 2400  | Auxiliary  | OVRD extension for .SECT	  |
     | 	     |    |    |       |	    | overlay control arguments	  |
     ----------------------------------------------------------------------
     













				      E-5







				  APPENDIX F

			MACREL COMMAND DECODER OPTIONS




	Option			  Function

	/A	  Deletes PDP-8/E symbols
	/B	  Prints listing file name in block letters
	/C	  Chains to KREF
	/E	  Enables error if links are generated
	/F	  Sends fast (brief) TTY error messages
	/G	  Chains to LINK after assembly and begins program
		  execution
	/H	  Passed to LINK
	/J	  Does not list unsatisfied conditional code
	/L	  Chains to LINK after assembly
	/M	  Includes the permanent symbols in the KREF output file
	/N	  Lists symbol table only
	/O	  Eliminates macro generation capability
	/P	  Resets line numbers to 0 for each page in the listing
	/Q	  Adds MQ (EAE) symbols
	/R	  Eliminates PAL8 symbols
	/S	  Omits symbol table from listing
	/V	  Passed to LINK
	/W	  Passed to LINK
	/X	  Sends extended TTY error messages
	/Y	  Cancels resident overlays
	/Z	  Eliminates BATCH
	/0-7	  Passed to LINK
	/8	  Passed to LINK
	/9	  Passed to LINK
	/=N	  Adjusts listing width
















				      F-1






				   APPENDIX G

		    DISCUSSION OF SELECTED ROUTINES IN LINK



     G.1  ADJPTR (LNKLSD)

     The routine ADJPTR adjusts SECTAB reference  pointers  to  be  forward
     pointers.   It also adjusts chained reference pointers to point to the
     first reference.   For example, it  would  change  the  condition:   B
     references  A  and C references B to:  B references A and C references
     A.



     G.2  ALLOC (LNKALL)

     The subroutine ALLOC uses SECTAB and the buffer (CIMAGE)  to  allocate
     memory  to  each  program section.   Beginning with the first entry in
     SECTAB, it performs the following steps:

	  1.  Searches CIMAGE for the  smallest  available  memory  segment
	      that  meets  the  field,  PC,  and length requirements of the
	      current program section.

	  2.  Allocates memory to that section.

	  3.  Updates CIMAGE.

	  4.  Scans the remainder of SECTAB for entries that reference  the
	      current entry and allocates memory to them at this time.

     If a program section does not fit into memory, its entry in SECTAB  is
     flagged by ALLOC and the allocation process is restarted with the scan
     by SECTAB.



     G.3  BULDTV (LNKBN2)

     BULDTV generates the overlay transfer vectors.  It creates a  transfer
     vector  for  each symbol in an overlay that is declared to be an entry
     (.ENTRY).  The vector provides the  information  needed  to  load  the
     overlay containing the referenced routine.







				      G-1
		    DISCUSSION OF SELECTED ROUTINES IN LINK


     G.4  CPIC (LNKALL)

     The subroutine CPIC creates the memory  image  tables  in  the  CIMAGE
     buffer  area  according to the user-specified Command Decoder options.
     The argument in the routine's calling sequence specifies  the  largest
     field  in  the memory picture.  It exits through the error return when
     the argument exceeds the number of the highest available memory field.
     The calling sequence is shown below:

	  (AC = 0)
	  JMS CPIC
	  arg
	  error
	  return

     where:

          arg	     is the number of the highest field to be  included  in
          	     memory allocation

	  error	     is the error return address

	  return     is the normal return address



     G.5  NEWBB (LNKBN2)

     The subroutine NEWBB is called whenever a new binary output buffer  is
     needed during loader image file construction.  NEWBB scans the list of
     available buffers  and  dumps  the  contents  of  the  least  recently
     accessed buffer to make room for a new buffer.



     G.6  NEWORG (LNKBN2)

     NEWORG is called whenever it finds a reference to the current location
     counter  in  an  input module.  It maps the referenced location into a
     block of the loader image file.  It calls  NEWBB  when  a  new  binary
     buffer is needed.



     G.7  PUTBIN (LNKBN2)

     PUTBIN inserts words, sequentially, into the  current  binary  buffer.
     When  the buffer is full, it calls NEWBB to send the buffer's contents
     to the memory image file and to supply a new buffer.






				      G-2
		    DISCUSSION OF SELECTED ROUTINES IN LINK


     G.8  RELOCA (LNKBN2)

     RELOCA relocates an entire input module, executing calls to NEWORG and
     PUTBIN.



     G.9  SEARCH (LNKMAN)

     The routine SEARCH searches the GST for a  symbol.   (During  pass  1,
     undefined  symbols  are  added  to  the  table.)  If a symbol is not a
     defined symbol, the GST entry is flagged as undefined and the count of
     undefined symbols is incremented.  If the symbol was found and this is
     defined, the definition is put in the GST and the count  of  undefined
     symbols is decremented.  An attempt to redefine a symbol will cause an
     error.  During pass 2 an  unsuccessful  search  results  in  an  error
     return.   A  successful  search  returns  with  the symbol's GST entry
     number in the AC.

     The calling sequence is:

	  JMS SEARCH
	  pass number
	  error return
	  normal return (AC=0 in pass 1)
			(AC=PTR in pass 2)



     G.10  SSORT (LNKALL, LNKLSD, and LNKMAP)

     SSORT performs an all-purpose bubble sort.  Its calling sequence is:

	  JMS SSORT
	  argl - the address of the table to be sorted
	  arg2 - length of table
	  arg3 - length of table entry
	  arg4 - the word to sort
	  arg5 - word mask (for example, 7600)
	  arg6 - type of comparison (for example, SNA)
	  return address














				      G-3





				     INDEX


		    A			  		 D


     ADJPTR, G-1			  DATE, 2-33
     AINIT, 2-11			  $DECIMA, 2-75
     ALLOC, G-1				  DELETE, 2-42
     .ASECT symbol table entry		  $DEVICE, 2-76
	 format, 1-13			  DIGIT, 2-63
     ASEMBL, 2-62			  $DISABL, 2-77
     ASEMLV, 2-62			  DPRINT, 2-67
     Auxiliary symbol table chunk	  .DSECT symbol table entry
	 entry format, 1-15		      format, 1-14


		    B					 E


     BACKL, 2-2				  $EJECT, 2-85
     BACKSL, 2-57			  $ENABLE, 2-76
     BACKUP, 2-60			  $ENPUNC, 2-83
     Binary buffer table (LDBUFS), 3-4 	  ENTER, 2-66
     BINFO, 2-82			  $ENTRY, 2-80
     BLKLET, 2-81			  EOS, 2-64
     BPUT, 2-53				  EQL, 2-60
     BPUTX, 2-88			  ERROR, 2-57
     BRAN, 2-61				  Error Typeout Routines, 2-26
     BRANCH, 2-61			  EXPOVR, 2-2
     BULDTV, G-1			  EXPR, 2-29
					  $EXPUNGE, 2-84
					  $EXTERN, 2-80
		    C			  .EXTERNAL symbol table entry
					      format, 1-13

     CALLIT, 2-64
     $CHAIN, 2-79					 F
     CHKFUL, 2-87
     CMNMOV, 2-46
     CNVADR, 2-55			  $FIELD, 2-85
     CONV, 2-42				  $FILENA, 2-75
     CORE, 2-34				  FIN0, 2-7
     Core image table (CIMAG, CIMAG1,	  FIN2, 2-14
	 CIMAG2, CIMAGE), 3-8		  FIN3, 2-20
     CPIC, G-2				  FIN5, 2-10
     CPYTOC, 2-12			  FINI, 2-60
     CREF, 2-65				  FINIO, 2-19, 2-37
     CREFX, 2-88			  $FIXMRI, 2-59
     CRLF, 2-67				  $FIXTAB, 2-84
     CTRLC, 2-60			  .FSECT symbol table entry
					      format, 1-15

				    Index-1
				 INDEX (CONT.)


		    G					  L


     GENUN, 2-44			  LETTER, 2-63
     GET, 2-60				  Library table (LIBTB), 3-12
     GETCHR, 2-60			  LIMSET, 2-34
     GETEX, 2-62			  LIST, 2-68
     GETFLG, 2-88			  $LIST, 2-83
     GETKAR, 2-65			  LISTER, 2-70
     GETLSD, 2-55			  LISTOR, 2-42
     GETOS, 2-39			  LNKALL, 4-1, G-1, G-2, G-3
     GETSYM, 2-58			  LNKBN1, 4-3
     Global symbol definition file	  LNKBN2, 4-3, G-1, G-2
	 (MGLOB.MA), 1-3		  LNKCAL, 4-4
     Global symbol table (GST), 3-2	  LNKCD, 4-5
     GLOB2, 2-80			  LNKCHN, 2-84
     $GLOBAL, 2-80			  LNKLSD, 4-8, G-1, G-3
					  LNKMAN, 4-5, G-3
					  LNKMAP, 4-10, G-3
		    H			  LNKMSG, 4-10
					  LOAD, 2-56
					  LOCPOP, 2-42
     HGHSCT, 2-56			  LOCPSH, 2-42
					  LOOKU, 2-43
					  LOOKUP, 2-65
		    I			  LOOP, 2-64
					  LSDINI, 2-18
					  LSDOUT, 2-16
     IDIV, 2-4				  LSTRET, 2-42
     $IFDEF, 2-73
     $IFNDEF, 2-73
     $IFNZRO, 2-72					 M
     $IFZERO, 2-73
     IGNORE, 2-55
     IMUL, 2-4			  	  MAC2, 2-52
     $INCLUD, 2-79			  MAC24, 2-55
     IOINIT, 2-13, 2-37			  MAC30, 2-66
     IONIT2, 2-14, 2-37			  MAC3R, 2-68
					  MACERR, 2-25
					  MACEXP, 2-29
		    J			  MACINI, 2-33
					  MACIO, 2-36
					  MACLIT, 2-43
     $JSW, 2-83				  MACMAC, 2-47
					  MACOPN, 2-48
					  MACORG, 2-49
		    K			  MACRO, 2-49
					  $MACRO, 2-47
					      format, 1-12
     KLU4, 2-66				  MACRTH, 2-51
     KLU10, 2-45			  MACTBL, 2-52
					  Main binary section table
					      (MBST), 3-10


				    Index-2
				 INDEX (CONT.)


     MC, 2-28				  OVRLIN, 2-70
     Memory segment control double	  OVRR, 2-82
	 words, 3-12			  OVRS, 2-84
     $MEXIT, 2-48			  OVRU, 2-85
     MGET, 2-40
     Module descriptor table
	 (MODTAB), 3-5					 P
     MORCRF, 2-88

					  $PAGE, 2-71
		    N			  PARSYM, 2-63
					  PART2, 2-47
					  PAS2, 2-86
     NEWBB, G-2				  PASS3, 2-70
     NEWORG, G-2			  $PAUSE, 2-55
     NEWPAG, 2-69			  Pointer table (PRTAB), 3-5
     NEX, 2-55				  POP, 2-65
     NEXTCHAR, 2-58			  $POP, 2-86
     NEXTT, 2-7				  PREFIN, 2-82
     $NOLIST, 2-83			  PREFORM, 2-35
     $NOPUNC, 2-83			  PRGLIT, 2-57
     NPRINT, 2-67			  PRGSPL, 2-45
     NUMLCL, 2-61			  PRINTY, 2-66
					  PRLINO, 2-66
					  PRN, 2-23
		    O			  PRNBIN, 2-68
					  PRNDSH, 2-68
					  PRNT2, 2-23
     $OCTAL, 2-75			  PRNT6, 2-25
     OFETCH, 2-42, 2-49			  PRZLIT, 2-57
     OFIX, 2-40				  Pseudo-macro symbol table
     ONCE, 2-34				      entry format, 1-12
     OPEN, 2-48				  Pseudo-operator table
     OPEN1, 2-8				      entry format, 1-13
     OPEN2, 2-8				  PUNBIT, 2-53
     OPEN3, 2-8				  PUNY, 2-54
     OPEN4, 2-10			  PURGEL, 2-45
     OPENTC, 2-49			  PUSH, 2-65
     OPRINT, 2-67			  $PUSH, 2-86
     ORET, 2-39				  PUTB, 2-54
     ORIG, 2-54				  PUTBIN, G-2
     ORIGIN, 2-62			  PUTBIT, 2-54
     OUT, 2-68				  PUTBN, 2-87
     OUTBLK, 2-81			  PUTBT, 2-87
     OUTDATA, 2-62			  PUTBUF, 2-42
     OUTLIT, 2-45			  PUTLC, 2-54
     OUTLST, 2-42			  PUTSYM, 2-58
     Overlay level information		  PUXBIN, 2-53
	 table (LNDR), 3-10
     Overlay transfer vector
	 (TRANVC), 3-8
     OVRA, 2-70
     OVRB, 2-72
     OVRD, 2-77

				    Index-3
				 INDEX (CONT.)


		    R					 U


     $RADIX, 2-75			  UNNAM, 2-54
     REIT, 2-13				  UPAROQ, 2-5
     $RELOC, 2-86			  User overlay level data
     RELOCA, G-3			      table (QUSRLV), 3-9
     ROTL6, 2-63
     .RSECT symbol table entry
	 format, 1-14					 V


		    S			  $VERSIO, 2-83


     $SBTTL, 2-85					 X
     SCAN, 2-60
     SEARCH, G-3
     .SECT table, 3-5
     SETIT, 2-57			  XPRINT, 2-23
     SETT, 2-67				  .XSECT symbol table entry
     SNGLQQ, 2-5			      format, 1-15
     SPOP, 2-41
     SPUSH, 2-40
     SSORT, G-3						 Z
     $START, 2-83
     STPRNT, 2-22
     SWBACK, 2-39			  $ZBLOCK, 2-71
     SWITCH, 2-38			  ZGET, 2-40
     SYMINI, 2-35			  ZINIT, 2-43
					  ZL, 2-44
					  ZLIT, 2-44
		    T			  ZPAD, 2-18
					  .ZSECT symbol table entry
     TAB, 2-68				      format 1-15
     TAGCOL, 2-62			  ZSECTG, 2-43
     TAGCOM, 2-62			  $ZTRNA, 2-80
     TASKY, 2-74
     TERM, 2-31
     $TEXT, 2-71
     $TITLE, 2-86
     TSTMAC, 2-63













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