Sum with call by value

 #include<stdio.h>

int sum (int a, int b);

int main(){

    int x=4, y=7;

    printf("The value of x and y is %d and %d\n", x, y);

    printf("The value of 4+7 is %d\n", sum(x, y));

    printf("The value of x and y after function call is %d and %d\n", x, y);

    return 0;

}

int sum (int a, int b){

    int c;

    c = a + b;

    b =3434;//doesn't change in main()

    a = 23432;  

    return c;

}