Logical Operators

And Operator

Used to perform a logical conjunction on two expressions.

Syntax: result = expr1 And expr2

Remarks: If, and only if, both expressions evaluate True, result is True.  If either expression evaluates False, result is False.  The following table illustrates how result is determined:

  Example: This example displays a message that depends on the value of variables A, B, and C, assuming that no variable is a Null.  If A = 10, B = 8, and C = 6, both expressions evaluate True.  Because both expressions are True, the And expression is also True.

A = GD(1)

B = GD(2)

C = GD(3)

If A > B And B > C Then 

Result = A

Else

Result = 0

End If

Not Operator

Used to perform logical negation on an expression.

Syntax: result = Not expr

Remarks: The following table illustrates how result is determined:

 If an integer variable has the value 0 ( False), the variable becomes -1 ( True); if it has the value -1, it becomes 0. 

Example: This example checks the opposite of the logical comparison of A and B, assuming neither variable is a Null.  If A = 10 and B = 8, the Not expression evaluates True because A is not equal to B.

A = GD(1)

B = GD(2)

If Not A = B Then              

Result = A

Else

Result = 0

End If

Or Operator

Used to perform a logical disjunction on two expressions.

Syntax: result = expr1 Or expr2

Remarks: If either or both expressions evaluate True, result is True.  The following table illustrates how result is determined:

 Example: This example displays a message that depends on the value of variables A, B, and C, assuming that no variable is a Null.  If A = 10, B = 8, and C = 11,  the left expression is True and the right expression is False.  Because at least one comparison expression is True, the Or expression evaluates True.

A = GD(1)

B = GD(2)

C = GD(3)

If A > B Or B > C Then

Result = A

Else

Result = 0

End If