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Comment by MeteorMarc | Hacker News Reader

60 bits must have been for historic reasons: https://en.m.wikipedia.org/wiki/Sexagesimal

The article explains the choice of 60 bits, which was indeed because of the many factors of 60.

"60 is a multiple of 1, 2, 3, 4, 5, and 6. Hence bytes of length from 1 to 6 bits can be packed efficiently into a 60-bit word without having to split a byte between one word and the next. If longer bytes were needed, 60 bits would, of course, no longer be ideal. With present applications, 1, 4, and 6 bits are the really important cases."

> If longer bytes were needed, 60 bits would, of course, no longer be ideal.

That seems like a weird conclusion for the engineers to come to, because 60 is also a multiple of 10, 12, 15, 20, 30 and (of course) 60 (the complement factors of 1, 2, 3, 4, 5 and 6), so a selection of longer bytes are very obviously available.

Given that they balked at the cost of moving up to 64-bit words, I guess moving up to 420-bit computing (for those 7-bit bytes) was out of the question ;-)

I think it's more a remark that of the first half dozen byte sizes all six fit evenly but of the next dozen only three do. This makes the divisibility not really hold that much value in the end. Particularly since six bits isn't enough to hold dual case alphanumerics and 3 types of punctuation.

It's not a convincing or complete explanation though. Why go so high, when other machines of the time were using 36 bits? And if they saved money by not going up to 64, why not go down to 48 for example?

It's explained in the article. But the reason is partially the same:

"60 is a multiple of 1, 2, 3, 4, 5 and 6. Hence bytes of length 1 to 6 bits can pe packed efficiently into a 60-bit word...

> the reason is partially the same

We do not know the actual reasons for the Sumerian number system. The best we have is post hoc claims and just so stories.

There is no indication that early computer science was beholden to the Babylonian number system "for historical reasons."

The big number of factors seems to be the most Occam's razor compatible reason to me in both cases. Doesn't mean the computer designers copied the idea from the Sumerians.

It was also common to use 5bit characters (in form of some variation of baudot coding) - the 6 bit characters were essentially early extension to it.

Which computer systems used 5-bit characters?

https://en.wikipedia.org/wiki/Baudot_code

I don't see any computers mentioned in that article. I don't consider a tele-printer to be a computer.

But early computers used teleprinters as I/O and that drove their character sets.

Which computers?

If you must:

https://dl.acm.org/doi/pdf/10.5555/1074100.1074162

Everything early on that used available baudot-code teletypewriters for input/output.

I'm familiar with baudot but teletypewriters aren't computers.

They were how you interfaced with them though. Either directly or indirectly through paper tape.

Which computers?

For one example among many, the original Bendix G-15's paper tape reader (the PR-1) only supported 5-bit paper tape, with the later PR-2 supporting 5-8bit tape.

http://www.bitsavers.org/pdf/bendix/g-15/T29_PR-1_Tech_Bulle...

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