Timeline for Why were programs entered on punch cards instead of paper tapes?
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| Apr 12, 2021 at 16:56 | comment | added | supercat | @Raffzahn: Depending upon what's on the tape, reading it backward may or may not be feasible. If a tape contains an Intel-hex file that uses only absolute addresses and never writes any byte twice, reading backward would be possible if an implementation can buffer an entire line. If a tape writes data and then patches it, however, reverse reading wouldn't work. | |
| Apr 11, 2021 at 18:19 | comment | added | dave | Offhand, the only fanfold tape usage I can dredge up from memory was on DEC machines. Were there others? | |
| Apr 11, 2021 at 17:57 | comment | added | davidbak | I assume the spoolers mostly worked. Fanfold stacking bins mostly didn't - or at least, it was a matter of luck. | |
| Apr 11, 2021 at 15:46 | comment | added | dave | That doesn't sound like you're passing the tape though the reader backwards (like magtape read-reverse would do) which is what I meant by my original tongue-in-cheek comment. | |
| Apr 11, 2021 at 15:37 | comment | added | Raffzahn | @another-dave What's difficult? Paper tape only delivers a series of characters. It doesn't matter what direction it's read. As soon as there is enough buffer the data can be collected and stored in reverse. The way I've seen collects a block of data in RAM, cleared with zeroes and filled high to low, writes it as BSAM to disk until end of tape. Simplyreading the BSAM blocks in reverse order presents the data as on the tape ... some leading zeroes added. | |
| Apr 11, 2021 at 15:04 | comment | added | dave | @Raffzahn - I find it difficult to believe in reading an entire papertape in reverse. Got a link? | |
| Apr 11, 2021 at 15:02 | comment | added | dave | The 2671 reader (page 24) can take its input from the centre of a spool of tape, so there's no reversal on the takeup spool. | |
| Apr 11, 2021 at 14:40 | comment | added | Raffzahn | @JohnDvorak Yes, they would have to be rewound - exactly like tapes. Still fast. Also, as Dave mentions, many readers could read in either direction, so it was up to the OS to buffer and reverse. | |
| Apr 11, 2021 at 12:50 | comment | added | dave | Maybe IBM papertape readers had 'read reverse' capability? ;-) | |
| Apr 11, 2021 at 9:09 | comment | added | John Dvorak | @Raffzahn wouldn't you still have to rewind the tape though, because the start is on the inside now? | |
| Apr 11, 2021 at 2:19 | comment | added | Raffzahn | There were quite fine and fast readers, winding paper tapes back onto spools. Much like with tape. | |
| Apr 11, 2021 at 0:58 | history | answered | dave | CC BY-SA 4.0 |