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Provide more sources and reword some sections.

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Nathaniel Beaver
2016-04-28 15:57:54 -05:00
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@@ -366,23 +366,30 @@ Unix was case-sensitive because Multics was case-sensitive.
Multics was case-sensitive because the ASCII standard Multics was case-sensitive because the ASCII standard
included both an uppercase and a lowercase alphabet. [#Multics_case_sensitive]_ included both an uppercase and a lowercase alphabet. [#Multics_case_sensitive]_
Why was ASCII case-sensitive? Why did ASCII do this?
It nearly wasn't. It was a close call, and almost didn't happen.
Telegraphy codes used uppercase only,
or at least did not distinguish upper and lowercase.
Even ITA2, an international standard from 1930,
used a 5-bit code with a shift to switch between letters and figures,
but not upper and lowercase. [#ITA2]_
Similarly, punched cards used uppercase letters only.
Early telegraphy codes did not distinguish upper and lowercase
because it would have slowed transmission speeds prohibitively.
Encodings with different bit patterns for uppercase and lowercase Encodings with different bit patterns for uppercase and lowercase
had been proposed as early as 1959, [#Bemer_1959]_ had been proposed as early as 1959, [#Bemer_1959]_
though they were not widely implemented. though they were not widely implemented.
For example, the IBM 7030 "Stretch" supercomputer used an 8-bit encoding For example, the IBM 7030 "Stretch" supercomputer used an 8-bit encoding
that included interleaved uppercase and lowercase alphabets, that included interleaved uppercase and lowercase alphabets,
and it was used at Los Alamos in 1961. and was used at Los Alamos as early as 1961.
[#Stretch_supercomputer]_ [#Stretch_supercomputer]_
The ASCII committee concluded that 6-bit encodings (64 bit patterns) Early on, ASCII committee concluded that 6-bit encodings (64 bit patterns)
were insufficient to include both control characters and special characters were insufficient to include both control characters and special characters
in addition to the required 26 alphabetics and 10 numerics, in addition to the required 26 alphabetics and 10 numerics,
so they decided to use a 7-bit code. so they decided to use a 7-bit code.
However, ASCII was designed to include a useful 6-bit subset,
which could only include single alphabet.
The consideration of a 6-bit, 64-character graphic subset was important The consideration of a 6-bit, 64-character graphic subset was important
to the standards committee. If the ultimate decision was that columns 6 to the standards committee. If the ultimate decision was that columns 6
@@ -412,15 +419,22 @@ wanted to reserve the remaining space for control characters.
--- Ibid, p.232 --- Ibid, p.232
Thought the comittee first formed in 1961, Though the comittee first formed in 1961,
it wasn't until late 1963 that they finally agreed to include a lowercase alphabet. it wasn't until late 1963 that they finally agreed to include a lowercase alphabet,
largely because of the influence of the
International Telegraph and Telephone Consultative Committee (CCITT).
At the first meeting of ISO/TC97/SC@ in 1963 October 29-31, a resolu- At the first meeting of ISO/TC97/SC2 in 1963 October 29-31, a resolu-
tion was passed that the lower-case alphabet should be assigned to tion was passed that the lower-case alphabet should be assigned to
columns 6 and 7. columns 6 and 7.
--- Ibid, p. 246 --- Ibid, p. 246
The ISO proposal, though, did not include the lower case alphabet and the
five accent marks that the CCITT considered essential.
--- Eric Fisher, "The Evolution of Character Codes, 1874-1968", p.22
Why is it useful for filenames to include upper and lowercase? Why is it useful for filenames to include upper and lowercase?
It can make filenames more intelligible, It can make filenames more intelligible,
@@ -559,7 +573,22 @@ For example, the Linux port of the `Unity engine`_ has `issues with case-sensiti
Everything in Multics is case sensitive; Multics permits use of the full Everything in Multics is case sensitive; Multics permits use of the full
upper and lower case ASCII character set. upper and lower case ASCII character set.
http://www.multicians.org/mgc.html Multics command names and programming languages use lowercase by
convention, but users are free to use uppercase letters in path names,
identifiers, user names, etc.
http://www.multicians.org/mgc.html#commandlanguage
Multics was one of the first systems to use upper and lower case letters
freely.
http://www.multicians.org/mga.html#ASCII
Obviously, BCD had no lower-case characters, and Multics did not use BCD
at all, except to output log and crash and tape mount messages from ring
0 to the primitive Selectric operator's console.
http://www.multicians.org/mgb.html#BCD
Since the Multics file system distinguished between upper and lower case, Since the Multics file system distinguished between upper and lower case,
external names had to be case sensitive, and without much discussion we external names had to be case sensitive, and without much discussion we
@@ -567,6 +596,14 @@ For example, the Linux port of the `Unity engine`_ has `issues with case-sensiti
http://www.multicians.org/pl1.html http://www.multicians.org/pl1.html
.. [#ITA2]
See p. 9 of "The Evolution of Character Codes, 1874-1968", Eric Fisher.
http://trafficways.org/ascii/ascii.pdf
https://github.com/ericfischer/ascii
.. [#Bemer_1959] .. [#Bemer_1959]
Simple pattern of correspondence should exist between codes assigned to Simple pattern of correspondence should exist between codes assigned to