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On 4/27/17, 3:16 PM, Jon Paris wrote:
Many many moons ago when IT was in its infancy there was a category
of early "computing" devices known as tabulators.
. . .
Tabulators processed punch cards
. . .
But if totals etc. needed to be produced, then you needed to know
when the following card had different values
. . .
Welcome to the RPG cycle and level breaks! They were designed to
provide a simulation of the original punch card equipment.
P.S. Indicators (*IN03 etc.) are from the same heritage. By
connecting a wire from a specific column to an output that always
provided a current at a specific timing point you could "turn on" an
indicator when (say) column 1 contained a "5" or a different
indicator if it contained a "6".
Quite true. Tabulators were examples of what are more generally (and
formally) called "plugboard-programmable unit record machines."
IBM Rochester was a plugboard-programmable unit record machine factory.
The S/3 (the original ancestor of the IBM Midrange line) was created
because IBM wanted to build a better unit record machine. They very
specifically did NOT want a "minicomputer," because they didn't want
anything to compete with their full-sized mainframes. They were already
getting entirely too much competition from a little upstart called DEC,
that had introduced something called the PDP-1 a decade earlier.
RPG's traditional syntax, I'm told, is based on plugboards for unit
record machines. Which makes a great deal of sense, given what Jon just
said. The idea was, if you could wire a plugboard, you could code in
RPG. And so RPG became the predominant language for this new "better
unit record machine" because you didn't need to hire a "programmer"; you
could just put it in the hands of the kid in the mailroom who'd taught
himself (or herself) how to wire plugboards in his (or her) spare time.
(I find myself thinking of that scene in Hidden Figures, when Dorothy
looked at a maze of wiring that had the engineers stumped, instinctively
found and corrected the problem, and got the new mainframe going.)
--
JHHL
(FWIW, the Computer History Museum, in Mountain View, CA, has a restored
IBM 1401 and a restored DEC PDP-1, both of which are demonstrated on a
regular schedule. They also have a restored IBM RAMAC hard drive, that
they've managed to interface with a notebook computer for demonstrations.)
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