Contributor: CHRISTOPHER CHANDRA Bit 7 6 5 4 3 2 1 0 128 064 032 016 008 004 002 001 TO check IF the last bit (7) is on OR off, you can DO something like.. FUNCTION isBitOn (n, b : BYTE) : BOOLEAN; BEGIN isBitOn := ( (n SHR b) AND 1) = 1 END; TO SET a specific bit TO on, DO something like... PROCEDURE setBitOn (VAR n : BYTE;b : BYTE); BEGIN n := n OR (1 SHL b) END; PROCEDURE toggleBit (VAR n : BYTE;b : BYTE); BEGIN n := n XOR (1 SHL b) END;