From: "John M. Aldrich" <fighteer AT cs DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: keyboard problem!
Date: Sat, 06 Dec 1997 08:10:08 +0000
Organization: Two pounds of chaos and a pinch of salt
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Doug Gale wrote:
> 
> There is a big difference!
> 
> The BIOS call always reads the keyboard.
> 
> getch() reads from standard input, which may have been redirected at the
> command-line to read from a device or a file.

You might be right, if you were talking about getchar().  But getch() is
a conio function that reads a single
keystroke from the BIOS keyboard interrupt.  The relevant code is in
src/libc/pc_hw/co80/conio.c:

int
getch(void)
{
  __dpmi_regs regs;
  int c;
  if (char_avail)
  {
    c = ungot_char;
    char_avail = 0;
  }
  else
  {
    regs.x.ax = 0x0700;
    __dpmi_int(0x21, &regs);
    c = regs.h.al;
  }
  return(c);
}

I don't know if this is functionally equivalent to reading from 0x16.

To the original poster:  I suggest you look in the DJGPP sources to see
exactly how the conio functions handle all the various keyboard-related
issues.  Also, a big tip:  use __dpmi_int instead of int86 for most
interrupt-related functions.  Not only does it support more functions,
but it also handles things like zeroing the stack pointer and other
overhead work.

hth

-- 
John M. Aldrich, aka Fighteer I <fighteer AT cs DOT com>

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