Punch cards

Robert Rabinoff rar113 at columbia.edu
Fri Apr 4 07:23:11 UTC 2008


When I first learned to program in 1964 we used an IBM 1620, fondly known
as CADET (Can't Add, Doesn't Even Try).  It had 20,000 memory cells, each
of which stored one decimal digit.  Words were delimited by a flag bit in the
most significant digit -- i.e. they were variable length.  Since there were no
integrated circuits then, the whole desk-sized machine, complete with blinking
lights, console switches, and a built-in IBM Executive electric typewriter for
small amounts of input and output, was made with individual transistors.  My
ex could type faster than that machine, especially with a Selectric, but this
was before the Selectric too.

For larger amounts of input or output one of course used the read-punch unit.
You typed your Fortran program on a keypunch, went to the machine, set the
switches, read in a deck with the Fortran compiler, reset the switches, read in
your program and it punched out the object code on a deck of cards.  If you 
needed any subroutines (sine, exp, etc.) they were on a separate deck you read
in and it punched out the necessary code.  Finally you took your compiled deck
from the punch side, reset the switches, and read it in and got your output off
the typewriter.  If you had a lot of output, you punched it to a deck of cards and
took them over to the listing machine, put in an appropriate pegboard to get the
formatting you wanted, and printed out the deck.

The variable word length was very useful for calculating Fibonacci numbers to
1000's of digits.  Incidentally, 3/5/08 last month is a Fibonacci date, the last
one for about 5 years till 5/8/13.  After that it's 8/13/21 and that's it for this
century.

Please do not bend, fold, staple or mutilate these cards.

Bob
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