100 /	P?S/8 FOCAL HDS 3200-30 OVERLAY
 110 
 120 /	LAST EDIT:	07-JAN-1990	05:00:00	CJL
 130 
 140 /	P?S/8 FOCAL OVERLAY FOR POINT, ETC. DISPLAY ON THE HDS 3200-30.
 150 
 160 /	THIS OVERLAY PROVIDES A DISPLAY FUNCTION TO P?S/8 FOCAL SIMILAR TO FOCAL-12
 170 /	OR BASIC-RT.
 180 
 190 /	IMPLEMENTATION RESTRICTIONS:
 200 
 210 /	THE SERIAL INTERFACE TO THE HDS TERMINAL IS RUN WITH  INTERRUPTS OFF;  FOCAL'S
 220 /	INTERRUPT  HANDLER MUST NOT USE THIS DEVICE.  THEREFORE, THE DEVICE  CAN'T  BE
 230 /	03/04,  OR  ANY  OTHER  DEVICE  CONTROLLED  BY  THE SYSTEM CONSOLE OVERLAY (IF
 240 /	PRESENT).
 250 
 260 /	THERE IS NO AUTOMATIC WAY TO RESTORE THE TERMINAL TO TEXT MODE.  THE USER MUST
 270 /	RETURN  THE  TERMINAL  TO TEXT MODE USING THE TEXT/GRAPHICS KEY.  THIS MUST BE
 280 /	AVOIDED WHILE  THE  TERMINAL  IS  IN  GRAPHICS  MODE.    IF THE '/X' SWITCH IS
 290 /	INVOKED NO TERMINAL  INITIALIZATION  IS  PERFORMED,  THUS THE TERMINAL MUST BE
 300 /	RESTORED TO GRAPHICS MODE  IF  NECESSARY.  THE ALTERNATIVE APPROACH WOULD HAVE
 310 /	BEEN TO "LOCK OUT" THE  TEXT/GRAPHICS  KEY, BUT THIS WAS CONSIDERED TOO SEVERE
 320 /	FOR NORMAL USE.
 330 
 340 /	BOTH OF THE ABOVE PROBLEMS MUST  BE  SOLVED  BEFORE  ATTEMPTING TO USE THE HDS
 350 /	TERMINAL AS A CONSOLE DEVICE.
 360 	EJECT
 370 /	AVAILABLE FUNCTIONS:
 380 
 390 /	FDIS(X,Y)			DISPLAY POINT AT (X,Y).
 400 
 410 /	FDIS(X,Y,0,"STRING",S,R)	DISPLAY THE CONTENTS OF "STRING" AS CHARACTERS
 420 /					OF THE STATED SIZE  S WITH THE STATED ROTATION
 430 /					R.  THE LOWER LEFT-HAND  CELL  COORDINATE  FOR
 440 /					THE FIRST CHARACTER IS AT (X,Y).
 450 
 460 /	FDIS(X,Y,1,CHARACTER,S,R)	DISPLAY THE EVALUATION OF CHARACTER MOD 128 AS
 470 /					A SINGLE ASCII CHARACTER  OF THE STATED SIZE S
 480 /					WITH  THE  STATED  ROTATION  R.     THE  LOWER
 490 /					LEFT-HAND    CELL  COORDINATE  FOR  THE  FIRST
 500 /					CHARACTER IS AT (X,Y).
 510 
 520 /	FDIS(X,Y,2,VALUE,LENGTH,S,R)	DISPLAY  THE  EVALUATION  OF  VALUE AS NUMERIC
 530 /					CHARACTERS OF  THE  STATED  SIZE  S  WITH  THE
 540 /					STATED  ROTATION  R.    LENGTH  SPECIFIES  THE
 550 /					NUMBER  OF  SIGNIFICENT  DIGITS.    THE  LOWER
 560 /					LEFT-HAND CELL COORDINATE FOR THE  FIRST DIGIT
 570 /					IS AT (X,Y).
 580 
 590 /	FDIS(X,Y,3)			SET INITIAL VECTOR ADDRESS AT (X,Y).
 600 
 610 /	FDIS(X,Y,4)			DRAW  STRAIGHT    LINE   (APPROXIMATION)  FROM
 620 /					PREVIOUS VECTOR ADDRESS  TO  (X,Y).  THIS ALSO
 630 /					SETS  UP  AN  INITIAL  VECTOR  ADDRESS  FOR  A
 640 /					SUBSEQUENT USAGE OF FDIS(X,Y,3) (EQUIVALENT TO
 650 /					INVOKING FDIS(X,Y,2) WITH THE CURRENT X  AND Y
 660 /					VALUES).
 670 
 680 /	FDIS(0)				CLEAR ALL POINTS FROM GRAPHICS SCREEN.
 690 
 700 /	FDIS(NON-ZERO)			IGNORED (PROVIDED FOR COMPATIBILITY WITH OTHER
 710 /					OVERLAYS  WHICH  USE  THIS  FUNCTION  TO  SHOW
 720 /					"GROWING" DISPLAYS).
 730 
 740 /	FIO(NEGATIVE)			RETURNS NUMERICAL VALUE (MODULO  128)  OF  THE
 750 /					NEXT  AVAILABLE  ASCII CHARACTER TYPED  (P?S/8
 760 /					FOCAL  WILL  WAIT  FOR  INPUT  IF  NECESSARY).
 770 /					SINCE INTEGER EVALUATION IS USED, THE ARGUMENT
 780 /					MUST BE NEGATIVE OR WITHIN THE RANGE 2048-4095
 790 /					MOD 4096.
 800 
 810 /	FIO(CHAR<2048)			OUTPUT  AN ASCII  CHARACTER.    SINCE  INTEGER
 820 /					EVALUATION  IS  USED,  THE  ARGUMENT  MUST  BE
 830 /					POSITIVE  AND  BETWEEN  0000-2047  MOD   4096.
 840 /					NORMAL  OUTPUT  DEVICES  GENERALLY  REDUCE THE
 850 /					CHARACTER  VALUE  RANGE  TO  0000-0255 MOD 256
 860 /					ALLOWING ANY  COMBINATION  OF  ASCII CHARACTER
 870 /					OUTPUT WITH OR WITHOUT PARITY SET.
 880 	EJECT