Ken ShirriffThe Computer History Museum has a presentation tonight on the history of computer dating: "Algorithms of Love". I made a special punch card for the event. It wasn't easy to make this card so I'll explain how I did it...
To make the heart, I had to figure out the right sequence of characters to form the hole pattern. Inconveniently, some holes don't form valid characters, so I had to "multi-punch" in some columns. This worked for one card, but the keypunch can't duplicate multi-punched cards.
To duplicate the heart cards, I toggled a short program into the 1401 computer to read a card and print out copies. The 1401 has a special feature called "column binary" that allows it to read and punch cards even if the hole pattern isn't valid.
The card reader/punch (IBM 1402) can punch 250 cards per minute, so the heart cards zipped out at high speed. However, this machine can't print text on cards, so I needed to go back to the keypunch...
Steve Bellovin@kenshirriff 1403? That was a printer, not a card read/punch.
Mike Stockdale@SteveBellovin @kenshirriff 1402 was the card read/punch.
@SteveBellovin @kenshirriff P.S. I love your posts, Ken. Don't mean to be nit picking :)
@mikes @kenshirriff Tnx. Models of the 1403 survived into the S/360 era, so I had *lots* of experience with them. (360s used 2540 card/read punches, which can read 1000 cards/minutes and (per Wikipedia) punch at 300 cpm.)
The later 1403s were enclosed in a sound-absorbing cover which could open automatically or (I think) under program control. Operators rapidly learned not to leave their coffee cups or boxes of punch cards on top…
The later 1403s were enclosed in a sound-absorbing cover which could open automatically or (I think) under program control. Operators rapidly learned not to leave their coffee cups or boxes of punch cards on top…