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.

Schezuk
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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'. – dave Apr 13 '21 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 '21 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 '21 at 09:20

1 Answers1

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.

Walter Mitty
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