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Aug 28th, 2007

Stupid Question

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I start C tomorrow and reading my book. When I run and compile this code it comes up in DOS and runs the code but then the DOS window closes. I'm new with C, can someone tell me why the DOS window flashes and then closes? Here's my code:

C Syntax (Toggle Plain Text)
#include <stdio.h>
 
int main( void )
{
    printf( "\t\"whoops\b\b\b\bew\n\"\n");
 
    return 0;
}
#include <stdio.h>

int main( void )
{
    printf( "\t\"whoops\b\b\b\bew\n\"\n");

    return 0;
}

Thanks

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Lost in Code...

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Aug 28th, 2007

Re: Stupid Question

It's for some reasons better to compile and run the programs using command line, but if you want to use ide, then you may write something like this in the end:

C Syntax (Toggle Plain Text)
printf ("== press enter ==\n");
getchar ();
printf ("== press enter ==\n");
getchar ();

Notice that you cannot use any other single character than newline for that, when you use only standard c, because in standard c the standard input is line buffered.

Last edited by TkTkorrovi; Aug 28th, 2007 at 2:23 pm.

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Aug 28th, 2007

Re: Stupid Question

Click to Expand / Collapse Quote originally posted by TkTkorrovi ...

It's for some reasons better to compile and run the programs using command line, but if you want to use ide, then you may write something like this in the end:
C Syntax (Toggle Plain Text)
printf ("== press enter ==\n");
getchar ();
printf ("== press enter ==\n"); getchar ();
Notice that you cannot use any other single character than newline for that, when you use only standard c, because in standard c the standard input is line buffered.

That seemed to do the trick, I'm a bit confused on the getchar() is it keeping the DOS window up because it's getting the charactor?

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Aug 28th, 2007

Re: Stupid Question

The window gets destroyed when the program ends. If you call getchar so that it blocks for input, the program doesn't end and the window isn't destroyed until getchar returns.

Last edited by Hamrick; Aug 28th, 2007 at 3:10 pm.

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Aug 28th, 2007

Re: Stupid Question

Click to Expand / Collapse Quote originally posted by TkTkorrovi ...

C Syntax (Toggle Plain Text)
printf ("== press enter ==\n");
getchar ();
printf ("== press enter ==\n"); getchar ();

This would be better

c Syntax (Toggle Plain Text)
printf("Hit 'ENTER' to exit\n");
fflush(stdout);
(void)getchar();
printf("Hit 'ENTER' to exit\n");
fflush(stdout);
(void)getchar();

Last edited by SpS; Aug 28th, 2007 at 10:50 pm.

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Aug 29th, 2007

Re: Stupid Question

So getchar is a function that's basically waiting for a charactor, thus keeping the DOS window open, correct?

I just want to make sure i'm understanding this correctly, thanks for your patients.

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Re: Stupid Question

Click to Expand / Collapse Quote originally posted by SpS ...

This would be better
c Syntax (Toggle Plain Text)
printf("Hit 'ENTER' to exit\n");
fflush(stdout);
(void)getchar();
printf("Hit 'ENTER' to exit\n"); fflush(stdout); (void)getchar();

I'd like to know more about why this is better. I understand the fflush to force the buffered printf output to the screen immediately. But why the cast to void for getchar's return value? Does this prevent allocation of bytes for the int ?

Last edited by hollystyles; Aug 29th, 2007 at 9:29 am.

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Aug 29th, 2007

Re: Stupid Question

Doesn't printing \n do the same thing as fflush?

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Re: Stupid Question

Click to Expand / Collapse Quote originally posted by hollystyles ...

But why the cast to void for getchar's return value? Does this prevent allocation of bytes for the int ?

Since some compilers (and lint) will warn about discarded return values, an explicit cast to (void) is a way of saying "Yes, I've decided to ignore the return value from this call.

Last edited by SpS; Aug 29th, 2007 at 12:43 pm.

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Aug 29th, 2007

Re: Stupid Question

you can use :

int main( void )
{
printf( "\t\"whoops\b\b\b\bew\n\"\n");

system("pause"); //stdio.h

return 0;
}

Last edited by ali_smith_14; Aug 29th, 2007 at 5:07 pm.

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