do ... while loop isn't working in main

Question

I wrote a simple program with a function that calculates the area of a circle. The program also asks to the user if he wants to calculate it again and if the input is 'N', the program is supposed to stop.

Here's the narrowed down test case:

#include<stdio.h>
#include<string.h>

int main(void)
{
    float r;
    char f;  
    do {    
        printf("Type the radius\n");
        scanf("%f", &r);
        printf("Repeat? [Press N for stop]");
        scanf("%c", &f);
    } while(f != 'N');
    getch();
    return 0;
}

but the loop never stops as it was intended to.

Do you have any suggestion?

Answer 1

scanf("%c", &f);

leaves a newline character in the input stream which is consumed in the next iteration. Add a space in the format string to tell scanf() to ignore whitespaces.

scanf(" %c", &f); // Notice the space in the format string.

Answer 2

replace

scanf("%c", &f);

with

f=getch();