Category 

Operators 

C++ Syntax  

if ( <condition1> )  <statement1> 

if ( <condition1> )  <statement1>;
 else  <statement2>;

if ( <condition1> )  <statement1>;
 else if ( <condition2> )  <statement2>;
 else  <statement3>;

if ( <condition1> ) 
{
  if ( <condition2> ) {
  <statement1>
  <statement2>
  }
  else <statement3>
}
else
  <statement4>

Description 

Use if to implement a conditional statement. 

You can declare variables in the condition expression. For example,

if (int val = func(arg))

is valid syntax. The variable val is in scope for the if statement and extends to an else block when it exists. 

The condition statement must convert to a bool type. Otherwise, the condition is ill-formed. 

When <condition> evaluates to true, <statement1> executes. 

If <condition> is false, <statement2> executes. 

The else keyword is optional, but no statements can come between an if statement and an else. 

The #if and #else preprocessor statements (directives) look similar to the if and else statements, but have very different effects. They control which source file lines are compiled and which are ignored.