Extra "10" printed after every conversion from ASCII to int.

eeepc4gsurf · 12-01-2009, 06:45 AM

Hello everyone. I have a very basic program which I wrote, to print the integer equivalents of an ASCII character. The code is below:

Code:

#include<stdio.h>

int main(void)
{
    char c;
    while (1)
    {
        scanf("%c", &c);
        printf("%d\n", c);
    }
}

The code is supposed to take a character as input and print the integer equivalent of that character. But the problem is that, after printing the integer equivalent, it prints an extra '10', every time.

Code:

My question is: Why does this extra '10' always come? When the code is just a simple:

Code:

#include<stdio.h>

int main(void)
{
    char c;
    scanf("%c", &c);
    printf("%d\n", c);
}

The code works just fine. There is no extra '10' displayed. I am using Ubuntu 9.10 with gcc-4.4.1.

Thanks in advance

Guttorm · 12-01-2009, 06:53 AM

The reason is that you hit enter after the character, and its ascii value is 10. Stdin is line buffered so when you type a character, the character is put in the buffer. The scanf don't get the character until a newline is met. It then reads the character + the newline next time in the loop.

eeepc4gsurf · 12-01-2009, 07:03 AM

So what can I do to stop this behaviour?

Hko · 12-01-2009, 07:31 AM

Except for some exceptions, I would recommend against scanf().

Code:

#include<stdio.h>

int main(void)
{
    int c;

    while (1) {
        c = getchar();
        if (c == EOF) { /* Stop on end of file (or ctrl-d) */
            break;
        }
        getchar();  /* read but discard next char (newline) */
        printf("%d\n", c);
    }
    return 0;
}

eeepc4gsurf · 12-01-2009, 07:32 AM

Thanks.