C Pocket Reference

Name

if ... else

Synopsis

The if statement creates a conditional jump.

Syntax:

if (expression) 
                     statement1  [else  
                     statement2]

The expression must have a scalar type. First, the if statement’s controlling expression is evaluated. If the result is not equal to 0—in other words, if the expression yields “true”—then statement1 is executed. Otherwise, if else is present, statement2 is executed.

Example:

if (x > y)  max = x; // Assign the greater of x and y to 
else        max = y; // the variable max.

The use of else is optional. If the value of the controlling expression is 0, or “false”, and else is omitted, then the program execution continues with the next statement.

If several if statements are nested, then an else clause always belongs to the last if (in the given block nesting level) that does not yet have an else clause. An else can be assigned to a different if by creating explicit blocks.

Example:

if ( n > 0 
{  if ( n % 2 == 0 
     puts("n is positive and even");
}
else                        // Belongs to first if 
     puts("n is negative or zero");