Ken Shirriff
The 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...
Feb 4 at 10:16pmWeb
Show threadKen ShirriffFeb 4
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.
Show threadKen ShirriffFeb 4
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.
Show threadKen ShirriffFeb 4
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...
Show threadHannekeFeb 4
@kenshirriff 250/minute?? Dang that’s got to be fun to watch!
Show threadSteve BellovinFeb 4
@kenshirriff 1403? That was a printer, not a card read/punch.
Show threadMike StockdaleFeb 5
@SteveBellovin @kenshirriff 1402 was the card read/punch.
Show threadMike StockdaleFeb 5
@SteveBellovin @kenshirriff
Show threadMike StockdaleFeb 5
@SteveBellovin @kenshirriff P.S. I love your posts, Ken. Don't mean to be nit picking :)
Show threadSteve BellovinFeb 5
@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…
Show threadKen ShirriffFeb 5
@SteveBellovin Thanks, I meant the 1402 card reader/punch. I've edited it now.
Show threadMichael OrmsbyFeb 4
@kenshirriff The THINK placard is a nice touch. I used to work for IBM in the 1980s and I’d see them in the hallways.
Show threadpaulnewmanFeb 5
@kenshirriff this is so awesome, I was chatting to my Dad about the IBM 1400 series the other day - he was coding on them back in '62. Very cool stuff 🙂
Show threadNot a Spring OnionFeb 4

@kenshirriff
Would a two-pass approach have worked?

First duplicating a card with one pattern, then punching another pattern on top of it?

Show threadMarcin WicharyFeb 4
@kenshirriff /subscribe
Show threadJanne MorenFeb 4

@mwichary @kenshirriff
Ken's RSS feed is one of the highlights of the internet.

...for a certain kind of reader, it has to be admitted.

Show threadMichael SilvesFeb 4
@kenshirriff The card is upside down. The corner cut is always on top.
Show threadKen ShirriffFeb 4
@Datamorph I got most of them right side up, just not the one in the photo 🙂
Show threadMike StockdaleFeb 5
@Datamorph @kenshirriff Still a few of us around that remember :)
Show threadMichael SilvesFeb 6
@mikes Surely you must also remember the joke about how they buried Thomas Watson of IBM?
9-edge face down