CPP if and else

Controlling Flow with if and else Statements

Programs needs to take action based on a true condition, or another action based on a false condition.

For this we are using if and else statements which also both can be nested:

if (expression1) {
 if (expression2)
  statement1;
 else {
  if (expression3)
   statement2;
  else
   statement3;
  }
 }
 else
  statement4;

• If the expression followed by the if statements evaluates to true, statements after the if statement will be executed else the statements after a else starts executing.
• If more than one statement exists for either the true or the false part you need to surround the statements with braces ({}).

// Demonstrates if/else and 
// proper use of braces
// in nested if statements
#include <iostream>
int main()
{
  int number;
  std::cout << "Enter a number less than \n";
  std::cout << "5 or greater than 20: ";
  std::cin >> number;
  std::cout << "\n";
  if (number >= 5) {
    if (number > 20)
      std::cout << "Number is greater than 20!\n";
  }
  else                            
    std::cout << "Number is less than 5!\n";
  return 0;
}

Enter a number less than
5 or greater than 20: 23

Number is greater than 20!

You can download this example here (needed tools can be found in the right menu on this page).

The Conditional (Ternary) Operator.

(expression1) ? (expression2) : (expression3)

z = (x > y) ? x : y;
// returns x into z if x>y else z will be y