Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!lll-tis!ames!fxgrp!ljz
From: ljz@fxgrp.UUCP (Lloyd Zusman, Master Byte Software)
Newsgroups: comp.lang.c
Subject: Re: No Echo Input Under MS-DOS
Message-ID: <192@fxgrp.UUCP>
Date: 31 Dec 87 18:48:31 GMT
References: <11055@brl-adm.ARPA>
Reply-To: fxgrp!ljz@ames.arpa (Lloyd Zusman, Master Byte Software)
Followup-To: <11055@brl-adm.ARPA> elder@wpafb-info2.arpa (ELDER.GREG)
Organization: FX Development Group, Inc., Mountain View, CA
Lines: 58

In article <11055@brl-adm.ARPA> elder@wpafb-info2.arpa (ELDER.GREG) writes:
> ...
>I'm fairly new to C and am trying to write a program using the
>Here is the pixDeqce [sic] of code I am having trouble with:
>
>	printf("Enter a key: ");
>	key = getch();		/* Get keyboard character without echoing */
>	printf("\nYou entered %c\n", key);
>
>When I run the program the screen remains blank until I hit a key.  Only
>after pressing a key does the program then respond with "Enter a key: "
> ...

Try putting the following statement after the first printf() call:

    fflush(stdout);

Many implementations do not flush the output buffer until a specified
number of characters (often 512) or a newline is sent, so you would
have to do an explicit flush to get the string out to the terminal.
It also should flush when any input is done via getchar(), gets(),
fgets(), fgets(), etc., but you aren't using any of these here.
The second printf() call in your example contains newlines and this
causes the first stuff to get flushed.

The getch() call under MSDOS references a low-level operating system
function and bypasses the standard C I/O processing you would get via
getchar(), gets(), etc.  You need this function so that the user
doesn't have to type a carriage return after entering the character,
but the side-effect is that it isn't part of the C I/O processing and
hence doesn't do the flushing you would like it to do.  The fflush()
solves this problem.

Before any of you unix people complain, I might point out that the
Datalight C compiler under MSDOS has no analog to the ioctl() unix
calls for setting the tty mode.  Special MSDOS-specific routines, one
of which being getch(), are needed to do "raw" terminal I/O.

In case you don't know this, 'stdout' is the place that printf() writes
to, which is why it is used as the argument to fflush().  I'm pretty
sure that this would solve your problem.

Also, you would need

    #include <stdio.h>

before this code in order that the compiler knows what is meant by 'stdout'.
I suggest this because the code fragment you set us here would work just
fine without the inclusion of stdio.h, and hence you might not have
included it.

Good luck.


-------------------------------------------------------------------------
 Lloyd Zusman
 Master Byte Software
 Los Gatos, California	    	    	Internet:   fxgrp!ljz@ames.arpa
 "We take things well in hand."	    	UUCP:	    ...!ames!fxgrp!ljz