5

ASCII was presented on paper tape where the lower 5 bits cross sprocket holes as following

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While FIELDATA chose the other way

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I found placing the higher, flag bits at the narrow side appealing, since you have 5 consecutive bits on one side for 26 characters. but why the contrary way was chosen?

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REF: Character Codes

LINK: I don't see why punched card is any better than fanfold tape, but I digress.

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  • I don't know the answer, but note that paper tape did not begin with 8-channel tape. I'd therefore suggest looking at earlier standards, say for 5-channel tape, to see if this usage could be derived by 'extension'.
    – another-dave
    Apr 13, 2021 at 12:45
  • @another-dave Well, 5-bit baudot-murry tape is frequency optimized, thus in a rather ravelled order. It won't become a meaningful reference.
    – Schezuk
    Apr 13, 2021 at 13:18
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    I'd guess that it was mostly arbitrary along the lines of big endian and little endian or driving on the right or the left. This was a day when no one considered industry wide standards.
    – badjohn
    Apr 14, 2021 at 9:20

1 Answer 1

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10

If you want to read it as octal, having the low order 3 bits grouped together is handy. Many of the early ASCII tables showed the codes in octal. HEX makes more sense once your computers begin to work on 8 bit bytes, but earlier computers had units like 36 bit words that were divisible by 3, and this led people to use octal for a few years.

Punched cards are easier to edit. If you ever had a program on paper tape that was missing a single comma, you'll know what I mean.

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4
  • Wow, I didn't take octal numbers into account.
    – Schezuk
    Apr 13, 2021 at 11:58
  • As for tapes, I'm talking about using every fold of tape like a card. Plz see the link.
    – Schezuk
    Apr 13, 2021 at 11:58
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    I worked on non-byte orientated paper tape or card using systems for several years before meeting a byte oriented machine. I learned octal before hex and, at one time, I could read paper tape (but more slowly than punched cards).
    – badjohn
    Apr 14, 2021 at 9:19
  • I also leanred octal before hex.
    – Walter Mitty
    Apr 22, 2021 at 14:55

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