Odd loop does not work using %c [duplicate]

Question

I am leaning C programming. I have written an odd loop but doesn't work while I use %c in scanf().
Here is the code:

#include<stdio.h>
void main()
{
    char another='y';
    int num;
    while ( another =='y')
    {
        printf("Enter a number:\t");
        scanf("%d", &num);
        printf("Sqare of %d is : %d", num, num * num);
        printf("\nWant to enter another number? y/n");
        scanf("%c", &another);
    }
}

But if I use %s in this code, for example scanf("%s", &another);, then it works fine.
Why does this happen? Any idea?

Answer 1

The %c conversion reads the next single character from input, regardless of what it is. In this case, you've previously read a number using %d. You had to hit the enter key for that number to be read, but you haven't done anything to read the new-line from the input stream. Therefore, when you do the %c conversion, it reads that new-line from the input stream (without waiting for you to actually enter anything, since there's already input waiting to be read).

When you use %s, it skips across any leading white-space to get some character other than white-space. It treats a new-line as white-space, so it implicitly skips across that waiting new-line. Since there's (presumably) nothing else waiting to be read, it proceeds to wait for you to enter something, as you apparently desire.

If you want to use %c for the conversion, you could precede it with a space in the format string, which will also skip across any white-space in the stream.

Answer 2

The ENTER key is lying in the stdin stream, after you enter a number for first scanf %d. This key gets captured by the scanf %c line.

use scanf("%1s",char_array); another=char_array[0];.

Answer 3

use getch() instead of scanf() in this case. Because scanf() expects '\n' but you are accepting only one char at that scanf(). so '\n' given to next scanf() causing confusion.