Why is DEL's bit value 0xff (or 0255)? Because there was a gadget out there for editing paper tape. Yes. You could delete a character by punching out the rest of the holes in the tape frame. I used it once. It was ridiculous.
Was there anything that created these lace cards as part of normal operation? I'm guessing not, considering the ramifications.
What about programs that did this when they encountered bugs?
Because back then, people would write on wooden tablets covered with wax.
So.. next time you see a kludge and think of "historical reasons", consider that "historical" goes back much farther than 20th century. :)
The intent was that, when reading tape, DEL is ignored, because it's a position that was punched over with DEL, i.e. deleted.
Also, when punching tape, a key will punch its holes and (naturally) advance to the next character position. For DEL, that means you erase the character under the cursor, and then the next character is under the cursor. That is, it's a ‘forward’ delete. (I think it was DEC's VT2x0 series terminals that screwed that up for everyone.)
It's kind of appropriate that a typical TECO command line looks a lot like transmission line noise. :)
The archive tapes were saturated with insecticide, so bugs would not be inclined to chew up your stored info.
There were also separate mechanical duplicators, plus multi-layer tape so that ordinary terminals could make more than one copy in real time.
For RS-232 electrical reliability, it's hard to beat a design intended to allow any pins to be connected to + or - 25 volts or ground in any combination without doing any damage to the equipment at either end.
Plus not restricted to the minuscule cable-length specifications of USB, and to reach the rest of the conected (by phone) world, the same EIA open-source digital protocol was just modulated/demodulated to analog audio upon send/recieve.
Remember RS-232 was always expected to be at least building-wide if not site-wide, depending on the size of the site.
Ordinary data communication at relatiely slow speeds has benefits that might as well be taken advantage of when they are needed.
Of course no code was absolutely required for any of these processes, but you could still seamlessly share ASCII files between Apple, Commodore, DOS PC's etc. using native COM port commands.
To get more speed between two points, on early PC's you could get software to multiplex more than one COM port to handle a single data stream over multiple signal pairs.
When needed, this would require and tie up multiple phone lines to reach off-site but it worked, plus it was the same technique on your own local copper but then it was more feasible to be always on.
Many buildings were originally equipped with top-quality AT&T/Bell copper pairs each dedicated to a separate signal for each (prospective) phone line to each office through its on-site relay box. At the time many of these pairs were rapidly becoming idle with the arrival of the modern office multiline phone which ran on fewer pairs, or had its own dedicated wiring installed at deployment.
With Windows 9x, COM port multiplexing was built into Windows, and with the arrival of the 115Kbaud UART's you could theoretically get 460Kbaud between offices by running four 3-conductor DB9 cables from the phone access plate on the nearest office wall, and using a PC having connectors for the full 4 COM ports which had become standard on motherboards.
DB series are the size of old 'parallel' ports. DE are the common width, like DE15 for vga.
>Standard RS-232 as defined in 1962 used a roughly D-shaped shell with 25 physical pins (DB-25), way more than the physical protocol actually required (you can support a minimal version with just three wires, and this was actually common). Twenty years later, after the IBM PC-AT introduced it in 1984, most manufacturers switched to using a smaller DB-9 connector (which is technically a DE-9 but almost nobody ever called it that)
>Almost nobody ever called it that