Why were programs entered on punch cards instead of paper tapes? (opens in new tab)

(retrocomputing.stackexchange.com)

5 pointsbcaa7f3a8bbc4y ago6 comments

6 comments

Simple answer: There was already an enormous stock of data on punch cards.

So it's rather the other way round: While early computers, like the UNIVAC I, used tapes (in this case magnetic tape) in order to separate themselves from the IBM data empire, IBM was facing a hard competition for its conventional punch card appliances in the Bull Gamma 3, which lead to the massively successful IBM 1401. In this respect, the 1401 was just the next step after electromechanical punch card appliances. Compatibility to existing data stores was a major selling point for IBM computing equipment.

ksaj4y ago

One partial answer might be due to utility billing. Back in the 70's our phone bills always came with a punch card with "Do not fold or staple" written on them. You had to include the punch card with your cheque when paying the bill.

The card was envelope size, so it was easy to mail out and easy for the bill payer to carry around. But a paper tape would be pretty awkward to handle in this fashion.

4x5-Guy4y ago

From what I remember, paper tape was a slower input device, while cards could be read much faster. To make a change, you had to repunch the whole tape, while for cards you could just punch one card.

Plus punch cards were much nicer to write notes on, and stick in your pocket... :)

daly4y ago

On the other hand you could hand-punch paper tape with a little plastic thing, one hole at a time. That way you could "patch" a paper tape. I used to have tapes with patches on patches (overwrite memory with each patch). Eventually I had to "memory dump" new tape that "merged all the patches" to get a new "master tape"

good times.

hilbert424y ago

...And for bookmarks they're par excellence (I've still about a 2-inch stack of new ones specifically for that purpose).

cafard4y ago

Punch cards were also easier for bad typists to correct: put another one behind it, copy up to the last good column, resume typing. Teletypes for paper tape were harder for me to use.

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