G. Sharman, University of Southampton, Southampton,

England

The system provides for storing program files {or other files}

on the 580 Magnetic Tape with PDP-8, and recalling them

at will without altering the state of the rest of the computer.

In general principle, it is similar to the DECtape Library

System, and the only effective storage requirement is the

last page of memory.

At present, the system consists of three programs known as

BOOTSTRAP 1, BOOTSTRAP 2, and the LIBRARY Routines.

BOOTSTRAP 1 is a minimal loader program which resides in

the last page of memory. Its function is to rewind the tape

and load BOOTSTRAP 2 into the last page, automatically

transferring control to it. Bootstrap saves the area of core

to be used by the system as a record on the magnetic tape,

loads the LIBRARY Routines into core, and transfers control

to them.

The LIBRARY Routines comprise a Directory of the files on

tape, an Input-Output package, enabling communication

with the Teletype, and four system programs:

LIst Types out the names of files in the Directory

CAll Transfers a file into core and exits

DUmp Writes a file on tape, rewrites the Directory,

and exits

EXit Restores the computer to its original state, with

BOOTSTRAP 1 and BIN on the last page.

The magnetic tape subroutine and some control functions are

included in BOOTSTRAP 2. Each entry in the directory consists

of three words: the name of the file, its first location

in core, and the number of words it occupies. The capacity

of the directory is 22₁₀ entries.