4 ms·

> Perhaps it relates to using 36-bit words? Yep, before ASCII was standardized it was common for machines to be built with word-addressable memory and words t

> Perhaps it relates to using 36-bit words? Yep, before ASCII was standardized it was common for machines to be built with word-addressable memory and words that were multiples of six bits. Two octal digits easily represent a six-bit byte, just as two hexadecimal digits easily represent an eight-bit byte

pansa2 5y ago
> words that were multiples of six bits Why was six bits chosen? The modern use of eight bits seems more natural to me, being a power of 2.
- bombcar 5y ago
  Six bits is the first that can easily encode standard text.
  - schoen 5y ago
    Though "easily" is relative as Baudot code used only five bits: https://en.wikipedia.org/wiki/Baudot_code https://en.wikipedia.org/wiki/Baudot_code (with control characters to shift to other character sets!). Wikipedia says that the several six-bit character set standards for text were inspired by typewriters https://en.wikipedia.org/wiki/BCD_(character_encoding)#Examples_of_BCD_codes https://en.wikipedia.org/wiki/BCD_(character_encoding)#Examp... but they didn't represent lowercase (!). (2⁶ would have allowed you to represent lowercase but you would have to sacrifice a whole lot to do so -- as alphanumerics alone would use 62 positions, leaving you with maybe one position for a space and one punctuation mark, and no newline...) Apparently EBCDIC derives from IBM's 6-bit BCD codes https://en.wikipedia.org/wiki/EBCDIC https://en.wikipedia.org/wiki/EBCDIC and is interesting because it uses 8 bits, successfully represents lowercase, and leaves a ton of (non-contiguous) positions unspecified. Maybe our standards (no pun intended) are just shifting as we deal with more and more capable software, but I'd be inclined to say that seven bits "easily encode" standard English text, and six don't, on account of the lack of case distinction. (Although you could certainly choose to handle that with control characters, and I'm sure some 6-bit systems did so.)
    - bombcar 5y ago
      Yeah once you go to six bits (five is weird because it’s an odd number) you really start looking at seven - and seven is also odd (which is why seven + parity took off for awhile). But now you have eight and that should be good enough for anyone. Interestingly enough B talks about how the new computer can address a “char” and not just a whole word at a time.

pansa2 5y ago

> words that were multiples of six bits Why was six bits chosen? The modern use of eight bits seems more natural to me, being a power of 2.

bombcar 5y ago
Six bits is the first that can easily encode standard text.
- schoen 5y ago
  Though "easily" is relative as Baudot code used only five bits: https://en.wikipedia.org/wiki/Baudot_code https://en.wikipedia.org/wiki/Baudot_code (with control characters to shift to other character sets!). Wikipedia says that the several six-bit character set standards for text were inspired by typewriters https://en.wikipedia.org/wiki/BCD_(character_encoding)#Examples_of_BCD_codes https://en.wikipedia.org/wiki/BCD_(character_encoding)#Examp... but they didn't represent lowercase (!). (2⁶ would have allowed you to represent lowercase but you would have to sacrifice a whole lot to do so -- as alphanumerics alone would use 62 positions, leaving you with maybe one position for a space and one punctuation mark, and no newline...) Apparently EBCDIC derives from IBM's 6-bit BCD codes https://en.wikipedia.org/wiki/EBCDIC https://en.wikipedia.org/wiki/EBCDIC and is interesting because it uses 8 bits, successfully represents lowercase, and leaves a ton of (non-contiguous) positions unspecified. Maybe our standards (no pun intended) are just shifting as we deal with more and more capable software, but I'd be inclined to say that seven bits "easily encode" standard English text, and six don't, on account of the lack of case distinction. (Although you could certainly choose to handle that with control characters, and I'm sure some 6-bit systems did so.)
  - bombcar 5y ago
    Yeah once you go to six bits (five is weird because it’s an odd number) you really start looking at seven - and seven is also odd (which is why seven + parity took off for awhile). But now you have eight and that should be good enough for anyone. Interestingly enough B talks about how the new computer can address a “char” and not just a whole word at a time.