Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!lll-winken!uunet!attcan!lsuc!maccs!cs3b3aj
From: cs3b3aj@maccs.McMaster.CA (Three More Exams)
Newsgroups: comp.sys.ibm.pc
Subject: Re: MS-DOS puzzle #1
Summary: std???
Keywords: stderr stdin stdout command.com
Message-ID: <2535@maccs.McMaster.CA>
Date: 24 Apr 89 00:46:51 GMT
References: <6893@bsu-cs.bsu.edu> <2936@ihuxy.ATT.COM>
Reply-To: cs3b3aj@maccs.UUCP (Three More Exams)
Organization: McMaster U., Hamilton, Ont., Can.
Lines: 31

In article <2936@ihuxy.ATT.COM> vg55611@ihuxy.UUCP (55421-Gopal,V.P.) writes:
>I don't think MS-DOS has stderr defined.  I think at one point, a very early
>point (DOS 1.00 ?), it didn't even have stdin and stdout defined, you only
>had keyboard / display services.  Later, stdin and stdout were defined, and
>the keyboard/display services were mapped to these.  At that time, they
>could have added stderr services, but they didn't.
>If application programs and compilers seem to have stderr, I am quite sure
>that it is because they bypass DOS and use BIOS to write to the display
>directly.

   Some correct points, some incorrect ones.  Dos 1.* did not support any
form of redirection (it didn't have the "handle" concept at that point ...
all file I/O was done with file control blocks, and I/O to the console,
AUX, etc. was done with specific DOS calls cloned from CP/M).

   DOS 2.* and up added file handle support, and define five handles which
your program automatically receives:
   0:  Standard input, CON by default
   1:  Standard output, CON by default
   2:  Standard error, always connected to CON
   3:  Auxiliary, usually connected to COM1
   4:  List device (PRN), usually connected to LPT1

   So DOS _does_ have stderr, and if you write a C program which outputs
to stderr it will work without the compiler having to translate your output
statements into BIOS calls.
--
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! Stephen M. Dunn, cs3b3aj@maccs.McMaster.CA ! DISCLAIMER:           !
! I always wanted to be a lumberjack! - M.P. ! I'm only an undergrad !
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