Thread: printf error

Code:

#include <stdio.h>

Put that at the top of your program.

Notice the important changes in red:

Code:

#include <stdio.h>

int main(void)
{
  int this_is_a_number;

  printf( "please enter a number: " );
  fflush(stdout);
  scanf( "&#37;d", &this_is_a_number );
  printf( "you entered %d", this_is_a_number );
  getchar();
  
  return 0;
}

Originally Posted by coolboarderguy

Hi All,

JDGATX, why did you add the fflush(stdout) part? Cheers.

coolboarderguy

Since there is no newline ('\n') at the end of the format string for the printf, there is no guarantee that printf will actually output anything before scanf() is reading data from the keyboard. Further, there is no guarantee that the second printf outputs anything before getchar() is performed either, so putting a fflush(stdout) after the second printf would guarantee that too.

Many C runtime libraries will automatically flush stdout on request of input for stdin - but this is by no means guaranteed - it is typical undefined behaviour of the kind where nothing will go horribly wrong, but it will be annoying.

--
Mats