Confused a little

[hkapur97]

#include <iostream>
using namespace std;

void twice(int n) {
   n = 2 * n;
}

int thrice(int n) {
   return n * 3;
}

int main() {
   
   int x = 1;
   twice(x); //At this point, I expect x = 2
   cout << x << endl;

   int y = 2;
   cout << thrice(y) << endl;

}

Results:

1
6

Expected Results:

2
6

Why?

[vichu8888]

void twice(int n) , here n value cannot be changed as it is passed by value

pass n as reference

void twice(int& n)

[hkapur97]

okay, thank you.
today is my first day of learning C++, so I didn't know the difference.