Returns TRUE if an expression is false, and FALSE if an expression is true.

Syntax

NOT expression
expression
A logical expression whose value is logical, that is TRUE/FALSE, YES/NO.
Note: It is possible for an operand to evaluate to the Unknown value (?). For a NOT operation, the result is the Unknown value (?), if expression evaluates to the Unknown value (?).

Example

In this procedure, if the user enters the number of a Customer that does not exist, the procedure displays a message that the Customer does not exist and the user must try again. If the Customer does exist, the procedure displays the Name and Phone number of the Customer.

r-not.p 

REPEAT:
  PROMPT-FOR Customer.CustNum.
  FIND Customer USING Customer.CustNum NO-ERROR.
  IF NOT AVAILABLE customer THEN DO:
    MESSAGE "Customer with CustNum:" INPUT Customer.CustNum
      " does not exist. Please try another.".
    UNDO, RETRY.
  END.
  ELSE 
    DISPLAY Customer.Name Customer.Phone.
END.

See also

AND operator (logical), OR operator (logical)