The logical negation operator (!) reverses the meaning of its operand. The operand must be of arithmetic type (or an expression that evaluates to arithmetic type). The operand is implicitly converted to type boolean. The result is TRUE if the converted operand is FALSE; the result is FALSE if the converted operand is TRUE.
! Expression
> 10 i = 0
> 20 i = i + 1
> 30 PRINT i
> 40 IF !(i % 5) THEN END
> 50 GOTO 20
> RUN
1
2
3
4
5
OK