Program Control Instructions - IBM 1620 1 Manual

of 100 (i.e., 200-position record) and, there-
fore, the group mark was not written in disk
storage.
Program Control Instructions
Control (K-34)
Description. The Control instruction is used to
space, tabulate, and return the carriage of the 1620
Console Typewriter. The
Qs
and
Q9
digits must con-
tain the typewriter code, 01, and the
Qll digit must
specify the control code, as follows:
1 - Space
2 - Return Carriage
8 - Tabulate
The P address and the Q7 and QlO positions of
the instructions are not used.
Execution Time. Execution time depends on the
control function.
Control Function
~
Seek (SK-34)
See 1311 Disk Storage Drive instructions.
Set Flag (SF-32)
Description. A flag bit is placed at the P address,
and a C bit is either added or removed to maintain
correct parity. The original digit at the P address
remains unchanged. The Q part of the instruction
is not used.
Execution Time. T
==
200 JLsec.
Clear Flag (CF-33)
Description. If a flag bit is present at the P address,
it is removed and a C bit is added or removed to
maintain correct parity. The digit at the P address
remains unchanged. The Q part of the instruction
is not used.
Execution Time. T
==
200 JLsec.
Halt (H-48)
Description. The Halt instruction stops the 1620
in manual mode. With the computer in manual mode,
if the Start key is pressed, the 1620 changes to auto-
matic mode and executes the next instruction in se-
quence. The P and Q parts of the instruction are not
used.
Execution Time. T
==
160 JLsec.
No Operation (NOP-41)
Description. This instruction performs no operation
and advances the computer to the next instruction in
sequence. The P and Q parts of the instruction are
not used.
Execution Time. T
==
160 JLsec.
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