Timeline for Why were programs entered on punch cards instead of paper tapes?
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Apr 12, 2021 at 16:53 | comment | added | supercat | @another-dave: Agreed, for errors that are immediately noticed. My point was to suggest that rubout wasn't the only way of fixing things without having to cut and splice tape. | |
| Apr 12, 2021 at 16:41 | comment | added | dave | @supercat I know and have used those; but the case discussed here is "error noticed while typing", which is generally better handled by fixing it before it gets to the computer. | |
| Apr 12, 2021 at 16:27 | comment | added | supercat | @another-dave: Not only that, but there were ways of editing programs on paper tape without having to cut and splice tape. For example, one could print out a program including line numbers, and then use an editor program which would accept a tape of a program followed by a tape containing a list of required insertions, deletions, and replacements (specified using line numbers from the original program). That editor would then punch a new clean tape and print out a new listing with line numbers. | |
| Apr 11, 2021 at 21:45 | comment | added | DrSheldon | @another-dave: Correct. I had already updated the answer to point out that the all-holes-punched pattern 0x7f was deliberately added to ASCII to "rub out" a character on punch tape. | |
| Apr 11, 2021 at 21:38 | comment | added | dave | If every keypress commits holes to a punch tape, what do you do to fix it? Backspace the tape and press rubout - the latter being "all holes punched". Somewhere in the input chain, that'll be ignored. (I can't remember whether the backspace key on a flexowriter backspaced the tape, or whether you had to do it manually). | |
| Apr 11, 2021 at 21:07 | history | edited | DrSheldon | CC BY-SA 4.0 | add point about editing |
| Apr 11, 2021 at 20:16 | comment | added | Anthony X | I'd add to your answer that keying in a program is almost never an error-free process; when you mess up a line on a keypunch, you can simply discard the bad card and do-over on the next fresh card. If every keypress commits holes to a punch tape, what do you do to fix it? Punch tapes are useful for creating fixed patterns; I long ago wrote a program that would extract the appropriate data from a design file and generate a pattern file for an NC drilling machine; the machine could only accept prepared input from a punch tape. | |
| Apr 11, 2021 at 18:23 | comment | added | alephzero | The standard size for teletype tape rolls was about 1000 feet, which meant a complete roll would hold about 120kbytes of data. As another-dave said, you simply cut off the length you had used, and nobody bothered about "wasting" a few feet of left-over tape at the end of a roll. If you were using tape where you expected you would need to edit the data, the smart thing to do was insert a few inches of unused "runout" between each line of data, which arguably wasted a similar amount of paper as using punched cards. | |
| Apr 11, 2021 at 17:33 | comment | added | dave | If the roll is too long, you are wasting paper and increasing costs. You tear it off when you're done punching. Same as any continuous (roll or fanfold) paper supply in a printer. The optimal size of a roll of tape is "the largest that will fit in your punch and your reader". Conversely you could argue paper tape wastes less material than cards, since paper tape generally does not need unpunched data, outside of leader and trailer for the entire dataset. One character of data still takes a whole card. | |
| Apr 11, 2021 at 15:59 | history | answered | DrSheldon | CC BY-SA 4.0 |