IBM 709 General Information Manual page 46

load program. This program provides for the same
modification of the original code that could be ob-
tained by changing the original symbolic deck and
reassembling. Thus, in
SCAT,
program modifications
are given to the loading program and, for these
changes, the modify·and-Ioad program performs both
the first and second passes. In this sense, the loading
program is a full assembly program. When program
modifications are made with the loader, it produces
on request a new squoze deck or an absolute binary
deck, as well as the listing of the modified program.
In addition to the above operations, the modify-and-
load program performs checking operations for both
programmer and machine errors.
The input-output system permits writing of
1-0
pro-
grams designed for a particular customer's application.
Transmission macro-instructions are used and are
executed by a routine called the dispatcher. These
macros provide simultaneous input-output with com-
puting. Computing is interlocked with data transmis-
sion so that the computer will not attempt to use or
modify data to be completed. Transmission orders
are channel-stacked when required and subsequently
the dispatching of these orders on data channels is au-
tomatic when the channel is free. The programmer
may interrogate the dispatcher for the status of any
transmission at any point in the program. The check-
ing of input-output indicators is automatically ac-
complished by the dispatcher.
The MockDonald control system has been designed
to enable the automatic transition from one problem
to the next, to maintain a machine program log, to
aid in the parallel operation of tapes and main frame
processing and, in general, to perform many of the op-
erations that would normally be handled by a profes-
sional machine operator.
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