From: "John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Help
Date: Thu, 19 Feb 1998 18:49:52 -0500
Organization: Two pounds of chaos and a pinch of salt.
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Richard Ward wrote:
> 
> The key presses and exit routines wouk ok, (i have removed the some of
> the cases to make the below smaller), but the display routines do not
> work.  I have tested the print_at routine on its own and it works
> fine.
> 
> At this rate I think I will not continue programming as if this fools
> me god help me in the future.  All I can think of is that its
> something to do with the compiler not compiling the instructions in
> the right order, something with I have problems with Xenix 1987
> version.

>         print_at(20,1,"Enter Option : ");
>         result=getch();

It's as simple as this:  conio and stdio functions are not compatible. 
Specifically, stdout is line-buffered by default in DJGPP v2.01, which
means that the string, "Enter Option : " is not displayed on the screen
until one of the following occurs:

 - You print a newline.
 - You call fflush(stdout).
 - The internal stdout buffer overflows.
 - You call a stdio input function.

Note that getch() is a conio input function, and does not invoke the
fourth rule.  Similarly, gotoxy() is a conio positioning function, and
has no effect on the stdout buffer.  I recommend manually flushing
stdout inside your print_at() function; this should solve the problem
completely, if inelegantly.  For an even less elegant solution, you
could remove buffering from stdout.  A third solution would be to
rewrite print_at() to use conio output, especially since it calls
gotoxy().  A fourth solution will arrive when DJGPP v2.02 comes out; the
line buffering problem will be worked around.

It's generally a bad idea to mix stdio and conio functions no matter
what compiler you use.

-- 
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