unsigned char x = 0x1C; unsigned char y = 0x95; In binary x's value: 00011100 y's value: 10010101 ---------- --------- x | y : 10011101 In hex x's value: 0x1C y's value: 0x95 --------- -- x | y 0x9D (In decimal, x | y = 157.) The | operation is performed on each bit position k of its operands to produce the bit value in the k-th position of the result. The result bit is determined by the table right bit 0 1 ------ left bit 0| 0 1 1| 1 1