How to pass a function argument by value or reference in the programming language C++?

[SubhanUllah]

void f(int i) { i = i + 1; } 
void g(int &i) { i = i + 1; } 
 
int main() { 
        int i = 1; 
        f(i); // by value: i is still 1 
        g(i); // by reference: i is now 2 
        return 0; 
}