if

An control flow logic function used to execute an instruction or a block of instructions only if a condition is fulfilled. If the condition in the parentheses following the if is true, the instructions are executed.

if( expression ) statement1;

or

if( expression ) statement1;
elsestatement2 ;

Example

The following example checks whether characters with the ascii values 107 and 22 are alpha-numeric.

The if statement tests whether isalpha returns a non-zero value. If it does, the value is alpha-numeric. If not, the else clause prints a suitable message.

    if (isalpha(107))
        lr_output_message ("The value 107 is %c", 107);
    else
        lr_output_message ("The value 107 is non-alphabetic");

    if (isalpha(22))
        lr_output_message ("The value 22 is %c", 22);
    else
        lr_output_message ("The value 22 is non-alphabetic");

Example: Output: 
Action.c(4): The value 107 is k
Action.c(11): The value 22 is non-alphabetic