Chaining
Occasionally, a program might be required which exceeds 120 instructions (the internal
instruction capacity of Programma). Since only five of Programma's ten registers are recorded
on a magnetic card, there are five registers available for the storage of as many as eight
intermediate results requiring further processing. The procedure for 'chaining' program cards
requires that the program be "segmented" at some convenient point and that all significant
intermediate results be stored in M, A, R, Band C before concluding the first phase of the
program. Assume for example that we have intermediate results in the following registers
requiring further processing.
BEFORE M
A Z
R S
E /
A set of instructions similar to those which appear on this page
would be added to the program so that the operator, having
entered all x and y values, would depress the key Z which
d initialize a series of transfer operations to store
intermediate results between cards.
AFTER
A V
R S
……
…….
The first series of instructions of the subsequent card must
incorporate an RS instruction to transfer the contents of R
isters D and d prior to any arithmetic operation or
reference to the R register.
On the following pages is a typical program from the Olivetti Underwood program library which
illustrates many of the techniques described previously.
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