C++ If Else

C++ supports the usual logical conditions from mathematics and uses them to run different blocks of code. The idea is simple: if a condition is true, do one thing; otherwise, do something else.

The if statement

Use the if keyword followed by a condition in parentheses. If the condition evaluates to true, the code inside the curly braces runs. If it is false, that code is skipped entirely.

#include <iostream>
using namespace std;

int main() {
  int temperature = 30;

  if (temperature > 25) {
    cout << "It is a warm day.\n";
  }
  return 0;
}

The else statement

Add an else block to describe what should happen when the condition is false. Only one of the two blocks will ever run.

#include <iostream>
using namespace std;

int main() {
  int hour = 20;

  if (hour < 18) {
    cout << "Good day.\n";
  } else {
    cout << "Good evening.\n";
  }
  return 0;
}

The else if statement

When you have more than two possibilities, chain conditions together with else if. C++ checks each condition in order and runs the first one that is true, then skips the rest.

#include <iostream>
using namespace std;

int main() {
  int score = 82;

  if (score >= 90) {
    cout << "Grade: A\n";
  } else if (score >= 80) {
    cout << "Grade: B\n";
  } else if (score >= 70) {
    cout << "Grade: C\n";
  } else {
    cout << "Grade: F\n";
  }
  return 0;
}