Why this code doesn't work?

Question

#include <iostream>
using namespace std;

void sf(int a, int b){
int c = a / 100 * b;
}

int main() {
int c;
int x = 100;
int y = 10;
sf(x, y);
cout<<c<<endl;
return 0;
}

Answer 1

This should produce the result you're looking for:

#include <iostream>
using namespace std;

int sf(int a, int b){
return (a / 100 * b); // a = x, b = y, returns 10
}

int main() {
int x = 100;
int y = 10;
int c = sf(x, y); // c = 10
cout<<c<<endl;
return 0;
}

Answer 2

This code work but your sf function just do no modifications.
This is because a and b are no references and sf return nothing.
The c you declared in sf is not the one in main.