From: "John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: wierd problem
Date: Sat, 15 Nov 1997 18:15:39 +0000
Organization: Two pounds of chaos and a pinch of salt
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J P Morris wrote:
> 
> Presumably this only happens with UNIX C compilers.
> This never happened with Borland, and it had me confused for a while.

Not quite.  While Unix may use buffered output streams, it does _not_
have a conio interface.  So there can be no conflict between the two
like there is on DOS.  :)  Unix may use other types of direct screen
interface; I'm not an expert in those.

Anyway, ANSI makes no guarantees about the buffered status of stdout;
stating only that it can be anything from unbuffered to line-buffered. 
Borland, et. al., being 16-bit compilers, can send text directly to DOS
with little overhead, so it makes sense for them to be unbuffered. 
DJGPP, however, is a 32-bit compiler, and interfacing with the DOS
filesystem to write out text requires a PM<->RM mode switch, which is
fairly expensive in terms of cycles.  So it makes sense to write out
text as seldom as is legal within ANSI.

For a test of what I am saying, find any DJGPP program that produces
voluminous text output, and turn off stdout buffering with setbuf(
stdout, NULL );.  The resulting code should run noticeably slower than
before.

hth
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