are there some special about '\x1a' symbol

Steve Holden steve at
Wed Jan 14 08:35:53 CET 2009

Unknown wrote:
> On 2009-01-12, John Machin <sjmachin at> wrote:
>> I didn't think your question was stupid. Stupid was (a) CP/M recording
>> file size as number of 128-byte sectors, forcing the use of an in-band
>> EOF marker for text files (b) MS continuing to regard Ctrl-Z as an EOF
>> decades after people stopped writing Ctrl-Z at the end of text files.
> I believe that "feature" was inherited by CP/M from DEC OSes
> (RSX-11 or RSTS-11). AFAICT, all of CP/M's file I/O API
> (including the FCB) was lifted almost directly from DEC's
> PDP-11 stuff, which probably copied it from PDP-8 stuff.
> Perhaps in the early 60's somebody at DEC had a reason.  The
> really interesting thing is that we're still suffering because
> of it 40+ years later.
I suspect this is probably a leftover from some paper tape data formats,
when it was easier to detect the end of a file with a sentinel byte than
it was to detect run-off as end of file. It could easily date back to
the PDP-8.

Steve Holden        +1 571 484 6266   +1 800 494 3119
Holden Web LLC    

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