From: cowan@mercury.ccil.org (John Cowan)
Subject: [TUHS] Command-line options
Date: Sat, 26 Mar 2016 18:05:52 -0400 [thread overview]
Message-ID: <20160326220551.GD12921@mercury.ccil.org> (raw)
In-Reply-To: <4B49E73B-51BD-4834-AA8C-5F9F74BA784E@ronnatalie.com>
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Ronald Natalie scripsit:
> More strictly, UNIX doesn’t have “type” in a file. They’re
> just a bunch of bytes. It’s up to whoever is making the file to
> decide if the name conveys that information or a magic number does.
True. On the IBM PC AT I mentioned earlier, I needed a number of binary
file formats, as it was clear that ASCII-binary conversion was too slow
for the purpose. (Probably not true even then, but what did I know?)
So I duly assigned 16-bit magic numbers for each file format, and
#define'd them in the code. Where did the magic come from? They were
RAD50 encodings of three-letter file codes!
Johnny Billquist scripsit:
> On the PDP-8, you sometimes saw @ used as a prefix character in
> SIXBIT. So you'd use @M to get a CR, and @J for an LF, and @@ would
> mark the end of the string. But not for filenames. But in code, since
> you sometimes used SIXBIT for string constants as well.
Yes, I think that's what I was half-remembering.
--
John Cowan http://www.ccil.org/~cowan cowan at ccil.org
You are a child of the universe no less than the trees and all other acyclic
graphs; you have a right to be here. --DeXiderata by Sean McGrath
next prev parent reply other threads:[~2016-03-26 22:05 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-25 14:43 [TUHS] Is the Teletype the unsung hero of Unix? Aharon Robbins
2016-03-25 19:47 ` Jaap Akkerhuis
2016-03-25 21:03 ` Diomidis Spinellis
2016-03-28 20:12 ` scj
2016-04-01 14:06 ` Dave Horsfall
2016-04-01 22:41 ` Greg 'groggy' Lehey
2016-03-25 21:29 ` [TUHS] Command-line options Warren Toomey
2016-03-25 23:25 ` Greg 'groggy' Lehey
2016-03-26 2:10 ` John Cowan
2016-03-26 3:09 ` Charles Anthony
2016-03-26 19:43 ` Clem Cole
2016-03-26 20:54 ` Ronald Natalie
2016-03-26 22:05 ` John Cowan [this message]
2016-03-27 1:25 ` Dave Horsfall
2016-03-27 1:50 ` Charles Anthony
2016-03-27 2:01 ` Greg 'groggy' Lehey
2016-03-27 6:18 ` Random832
2016-03-27 6:57 ` Greg 'groggy' Lehey
2016-03-27 19:38 ` Dave Horsfall
2016-03-27 1:35 ` Greg 'groggy' Lehey
2016-03-26 3:54 ` [TUHS] Is the Teletype the unsung hero of Unix? Greg 'groggy' Lehey
2016-03-26 4:30 ` Steve Nickolas
2016-03-26 5:44 ` Greg 'groggy' Lehey
2016-03-26 8:33 ` Steve Nickolas
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