My factorial function is not returning factorial

Question

I am not able to find out why my function returns the user input only rather then the factorial of the input.

#include <stdio.h>
#include <math.h>
int factorial(int x)
{
    //int x;
    int sum = 1;
    while (x!=0){
        sum = sum * x;
        x--;
    }
    return sum;
}

int main(){
    int x;
    printf("Enter value of x: ");
    scanf("%i",&x);
    factorial(x);
    printf("sum is %i", x);
    
    return 0;
}

Answer 1

Your factorial function does return a new value, but then you don't actually use that value.

printf("sum is %i\n", factorial(x));

Note aso that you should be checking the return value from scanf. If scanf in this situation does not return 1, it's indicating a failure to read a value into x. If this is the case, the value of x is indeterminate, and the behavior of the following code is undefined.

An example of what might occur: if the initial value of x is a negative number, factorial only checks that it's input is equal to zero, but does not check if it's less than zero, so the loop might never terminate.

Answer 2

Because you are printing x which is the variable that you have stored the user input in. Your factorial function returns the result, but you are not saving it.