OpenEdge Development:<br />Progress 4GL Reference NOT operator

Release 10.1A: OpenEdge Development:
Progress 4GL Reference

NOT operator

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.
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.cust-num.
  FIND customer USING cust-num NO-ERROR.
  IF NOT AVAILABLE customer
  THEN DO:
    MESSAGE "Customer with cust-num:" INPUT cust-num
      " does not exist. Please try another.".
    UNDO, RETRY.
  END.
  ELSE DO:
    DISPLAY name phone.
  END.
END. 
See also

AND operator, OR operator