C++ if statement

An if statement consists of a boolean expression followed by one or more statements.

Syntax

The syntax of an if statement in C++ is −

if(boolean_expression) {
   // statement(s) will execute if the boolean expression is true
}

If the boolean expression evaluates to true, then the block of code inside the if statement will be executed. If boolean expression evaluates to false, then the first set of code after the end of the if statement (after the closing curly brace) will be executed.

Flow Diagram

Example

#include <iostream>
using namespace std;
 
int main () {
   // local variable declaration:
   int a = 10;
 
   // check the boolean condition
   if( a < 20 ) {
      // if condition is true then print the following
      cout << "a is less than 20;" << endl;
   }
   cout << "value of a is : " << a << endl;
 
   return 0;
}

When the above code is compiled and executed, it produces the following result −

a is less than 20;
value of a is : 10