... However I'm not sure how much I trust it. It says that 5x7 was "the usual PDP-6/10 convention" and was called "five-seven ASCII", but I can't find the phrase "five-seven ASCII" anywhere on Google except for posts quoting that Wikipedia page. It cites two references, neither of which contain the phrase "five-seven ascii".
Though one of the references (RFC 114, for FTP) corroborates that PDP-10 could use 5x7:
[...] For example, if a
PDP-10 receives data types A, A1, AE, or A7, it can store the
ASCII characters five to a word (DEC-packed ASCII). If the
datatype is A8 or A9, it would store the characters four to a
word. Sixbit characters would be stored six to a word.
To me, it seems like 5x7 was one of multiple conventions you could store character data in a PDP-10 (and probably other 36-bit machines), and Wikipedia hallucinated that the name for this convention is "five-seven ASCII". (For niche topics like this, I sometimes see authors just stating their own personal terminology for things as a fact; be sure to check sources!).
I like challenges like this. First, the edit that introduced the "five-seven ascii" is [1] (2010) by Pete142 with the explanation "add a name for the PDP-6/10 character-packing convention". The user Pete142 cites his web page www.pwilson.net that no longer serves his content. Sure it can be accessed with archive.org and from the resume the earliest year mentioned is 1986 ( MS-DOS/ASM/C drivers Technical Leader: ...). I suspect that he himself might have use the term when working and probably this jargon word/phrase didn't survive to a reliable book/research.
You do better with a search for "PDP-10 packed ascii". In point of fact the PDP-10 had explicit instructions for managing strings of 7-bit ascii characters like this.
That was true at the system level on ITS, file and command names were all 6 bit. But six bits doesn't leave space for important code points (like "lower case") needed for text processing. More practical stuff on PDP-6/10 and pre-360 IBM played other tricks.
The relevant Wikipedia page (https://en.wikipedia.org/wiki/36-bit_computing)indicates that 6x6 was the most common, but that 5x7 was sometimes used as well.
... However I'm not sure how much I trust it. It says that 5x7 was "the usual PDP-6/10 convention" and was called "five-seven ASCII", but I can't find the phrase "five-seven ASCII" anywhere on Google except for posts quoting that Wikipedia page. It cites two references, neither of which contain the phrase "five-seven ascii".
Though one of the references (RFC 114, for FTP) corroborates that PDP-10 could use 5x7:
To me, it seems like 5x7 was one of multiple conventions you could store character data in a PDP-10 (and probably other 36-bit machines), and Wikipedia hallucinated that the name for this convention is "five-seven ASCII". (For niche topics like this, I sometimes see authors just stating their own personal terminology for things as a fact; be sure to check sources!).
I like challenges like this. First, the edit that introduced the "five-seven ascii" is [1] (2010) by Pete142 with the explanation "add a name for the PDP-6/10 character-packing convention". The user Pete142 cites his web page www.pwilson.net that no longer serves his content. Sure it can be accessed with archive.org and from the resume the earliest year mentioned is 1986 ( MS-DOS/ASM/C drivers Technical Leader: ...). I suspect that he himself might have use the term when working and probably this jargon word/phrase didn't survive to a reliable book/research.
[1] https://en.wikipedia.org/w/index.php?title=36-bit_computing&...
You do better with a search for "PDP-10 packed ascii". In point of fact the PDP-10 had explicit instructions for managing strings of 7-bit ascii characters like this.
I've run into 5-7 encoding in some ancient serial protocol. Layers of cruft.
That was true at the system level on ITS, file and command names were all 6 bit. But six bits doesn't leave space for important code points (like "lower case") needed for text processing. More practical stuff on PDP-6/10 and pre-360 IBM played other tricks.