Mail Archives: djgpp/1997/10/20/22:17:27
Marsel wrote:
>
> #include <stdio.h>
> main()
> {
> char c;
> int n;
> printf("Write an integer: ");
> scanf("%d",&n);
> printf("Write a character: ");
> scanf("%c",&c);
> printf ("The integer is: %d and the character is: %d \n",n,c);
> }
>
> Why the secong scanf function does not wait until the caracter is introduced
> ?. the c variable always contain the caracter \010
> I know it will be better to use c=getch(); but why the this code does not
> work well ?
Because you have never bothered to read your C textbook thoroughly.
scanf() normally ignores whitespace in the input it parses, but "%c"
makes scanf() return the first character it reads, regardless of whether
it is whitespace or not. The first scanf() statement reads an integer,
leaving the newline ('\n') in the input buffer. The second scanf()
looks in the buffer, reads the newline, and returns it, without asking
you for more input.
You have a couple of solutions:
- flush the buffer after the first scanf() with "fflush( stdout );"
(this is ugly)
- read in an extra character to get rid of the blank space.
(this fails if more than one extra character is the buffer)
- use a loop to read until you encounter a newline:
while( getchar() != '\n' )
;
(this is the most commonly used method, IMHO)
- substitute getch() for the second scanf().
!!! WARNING !!!
getch() is a conio function, not a stdio function. Under DJGPP stdio
functions are line buffered and so you won't see the output from the
second printf() until after you read the character. This is not a bug
but a feature of DJGPP, and you can learn more about it in chapter 9.4
of the DJGPP FAQ (v2/faq210b.zip from SimTel or online at
http://www.delorie.com/djgpp/v2faq/).
hth
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