From: Paul Winalski <paul.winalski@gmail.com>
To: TUHS <tuhs@tuhs.org>
Subject: [TUHS] Re: Origins of the SGS (System Generation Software) and COFF (Common Object File Format)
Date: Sun, 26 Feb 2023 10:51:12 -0500 [thread overview]
Message-ID: <CABH=_VTaY5CifZO6DLjpDseQg+K_kY8rd_W6i1sQg3iUTRj8ng@mail.gmail.com> (raw)
On 2/25/23, Brian Walden <tuhs@cuzuco.com> wrote:
> It was originaly 205. See A.OUT(V) (the first page) at
> https://www.bell-labs.com/usr/dmr/www/man51.pdf it was documented as to
> why.
>
>
> The header always contains 6 words:
> 1 "br .+14" instruction (205(8))
> 2 The size of the program text
> 3 The size of the symbol table
> 4 The size of the relocation bits area
> 5 The size of a data area
> 6 A zero word (unused at present)
>
> I always found this so elegant in it's simplicity. Just load and start
> execution at the start (simplifies exec(2) in the kernel) I always wondered
> if this has done anywhere else before, or invenetd first in unix.
IBM's Basic Program Support (BPS) for System/360 was a set of
stand-alone utilities for developing and running stand-alone programs.
BPS/360 wasn't really an operating system because there wasn't any
resident kernel. You just IPLed (Initial Program Load; IBM-speak for
"boot") your application directly. So the executable format for BPS
had a bootstrap loader as the "program header". Not quite the same
thing as a.out's 205(8) magic number, but similar in concept.
I don't know of any other OS ABI that uses this trick to transfer
control to application programs.
Microsoft uses something similar in PECOFF. A PECOFF executable for
x86 or X86-64 starts with a bit of code in MS-DOS MZ executable format
that prints the message "This program cannot be run in DOS mode".
-Paul W.
next reply other threads:[~2023-02-26 15:51 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-26 15:51 Paul Winalski [this message]
-- strict thread matches above, loose matches on Subject: below --
2023-02-25 20:14 Brian Walden
2023-02-23 21:37 Paul Ruizendaal
2023-02-23 22:11 ` segaloco via TUHS
2023-02-24 0:07 ` segaloco via TUHS
2023-02-23 15:13 Noel Chiappa
2023-02-22 20:16 [TUHS] " segaloco via TUHS
2023-02-22 22:20 ` [TUHS] " Clem Cole
2023-02-23 0:17 ` segaloco via TUHS
2023-02-23 6:30 ` Lars Brinkhoff
2023-02-23 14:25 ` KenUnix
2023-02-23 19:37 ` Warner Losh
2023-02-24 17:01 ` Rich Salz
2023-02-23 16:49 ` Paul Winalski
2023-02-23 18:38 ` segaloco via TUHS
2023-02-23 20:40 ` Paul Winalski
2023-02-24 12:45 ` arnold
2023-02-24 13:13 ` Arno Griffioen via TUHS
2023-02-25 19:28 ` arnold
2023-02-25 19:34 ` Steffen Nurpmeso
2023-02-24 14:01 ` Harald Arnesen
2023-02-25 2:07 ` Dave Horsfall
2023-02-25 15:30 ` Clem Cole
2023-02-25 17:29 ` Paul Winalski
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