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

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