Re: Control characters (was: furigana etc.)

From: Edward Cherlin (
Date: Sat Jul 08 2000 - 01:58:14 EDT

At 4:11 PM -0400 7/4/00, John Cowan wrote:
>On Mon, 3 Jul 2000, Edward Cherlin wrote:
> > *Some* computer system designers, noticing
> > that the demands of printing terminals were not requirements on
> > system file internals, chose to use either CR alone or LF alone for
> > line or paragraph ends, all without coordination.
>IIRC, the Model 37 Teletype interpreted 0A as a newline function,
>so ASCII allowed 0A to be interpreted as either LF or NL. (Later,
>these functions were assigned to the separate 84 and 85 control
>characters, but the 80-9F range never really caught on...)
>The Unix folks therefore adopted 0A as the internal end of line character,
>conformantly to ASCII rules.
> > The use of 1A SUB for end of file in several operating systems
> > including PCDOS is a violation of the ASCII standard, which provides
> > both 03 ETX (End of Text) and 04 EOT (End of Transmission), but who
> > cared?
>I think that TOPS-10 was the first OS to use this convention; if not
>used there, it was certainly present in OS/8.

Gary Kildall copied this usage from one of the DEC operating systems
into Digital Research's CP/M and later CP/M-86. Seattle Computing
naturally followed along in its CP/M-86 clone, which Microsoft bought
up to use as the basis for PCDOS. [sigh]

>OS/8 did not record the
>exact length of a file, but only the number of blocks it contained;

CP/M did the same.

>the convention was to fill out the final block with 1A characters,
>which were ignored by text processes. The same thing was done with
>binary paper tape images, which were the canonical representation on OS/8 of
>non-executable object files. Some programs inserted only a single 1A,
>which then came to be thought of as an EOF mark. Presumably, since 1A
>is Control-Z, there was some vague notion of Z=End.
>DEC OSes notoriously distorted or misused the control characters, thus
>^U = NAK was used to kill an input line instead of ^X = cancel.
>John Cowan
> "You need a change: try Canada" "You need a change: try China"
> --fortune cookies opened by a couple that I know

Edward Cherlin
"A knot!" exclaimed Alice. "Oh, do let me help to undo it."
Alice in Wonderland

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