ID Number: Q45563
5.10 6.00 6.00a 6.00ax 7.00
MS-DOS
Summary:
In Microsoft C versions 5.0, 5.1, 6.0, 6.0a, 6.0ax, and C/C++ version
7.0, getchar() will wait for a carriage return even if setbuf() is used
to unbuffer stdin.
More Information:
The function setbuf() affects a stream file buffer, such as stdin, but
has no effect on the keyboard or MS-DOS device buffers. The stream I/O
function getchar() can read a character from the keyboard buffer only
when the keyboard buffer is flushed by either being filled, by a
carriage return, or by an interrupt 0x21, function 0xC call.
To read normal 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. For more information on this
function, query on the following word in the Microsoft Knowledge Base:
_bios_keybrd()
The following example demonstrates the difference between using
getchar() and getch().
Sample Code
-----------
/* Compile options needed: none
*/
#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");
}
Additional reference words: 5.00 5.10 6.00 6.00a 6.00ax 7.00