ifdef in cpp code example

Example 1: if c++

int x = 20;
int y = 18;
if (x > y) {
  cout << "x is greater than y";
}

Example 2: if c++

#include<iostream>
using namespace std;
int main(){
	int eta; 
	cout<<"Ciao Utente inserisci la tua eta'! "<<"\n";
	cin>>eta;
	if(eta >= 18){
		cout<<"Benvenuto al cinema!";
	}
}