!                       Logical NOT Operator (unary)

 !exp                    logical NOT
 exp                     any integral type (int, char, enum, etc.)

    The unary operator ! performs a logical inversion on exp.  If exp has
    a value of 0 (FALSE), then !exp has a value of 1 (TRUE).  If exp has
    a non-zero value (TRUE), then !exp has a value of 0 (FALSE).  Here
    are two examples:

           j = 0x0F01;
           i = !j;              /* i == 0x0000 */

           j = 0x0000;
           i = !j;              /* i == 0x0001 */