README.md

layout	title	permalink
page	Q45563: setbuf() Does Not Control Buffering of DOS or Keyboard Buffer	/pubs/pc/reference/microsoft/kb/Q45563/

Q45563: setbuf() Does Not Control Buffering of DOS or Keyboard Buffer

Article: Q45563
Version(s): 5.10
Operating System: MS-DOS
Flags: ENDUSER | S_QuickC
Last Modified: 25-JUL-1989

Question:

Why does getchar() still wait for a carriage return even though I used
setbuf() to unbuffer stdin?

Response:

The function setbuf() affects a stream file buffer like stdin, but has
no effect on the keyboard or DOS device buffers. The stream I/O
function getchar() can only read a character from the keyboard buffer
when the keyboard buffer is flushed by either being filled, by a
carriage return, or by an interrupt 0x21, function 0xC call.

To read typical characters directly from the keyboard, you can use
the console I/O function getch(). To read control codes such as
ALT+Q (echo subsequent output to printer) or ALT+R (pause output), you
can use the _bios_keybrd() function. Query on the following:

   _bios_keybrd()

The following example demonstrates the difference between using
getchar() and getch():

#include <stdio.h>
#include <conio.h>

void main (void)
{
   setbuf (stdin, NULL);        /* cause stdin to be unbuffered */
   if (getchar () != EOF )
      printf ("getchar() still waits for return key\n");
   if (getch () != EOF )
      printf ("getch() does not wait for return key\n");
}