Example: Suppose in byte that has a value 10101101 . We wish to check whether bit number 3 is ON (1) or OFF (0) . Since we want to check the bit number 3, the second operand for AND operation we choose is binary 00001000, which is equal to 8 in decimal.
ANDing operation :
10101101 original bit pattern
00001000 AND mask
00001000 resulting bit pattern
The resulting value we get in this case is 8, i.e. the value of the second operand. The result turned out to be a 8 since the third bit of operand was ON. Had it been OFF, the bit number 3 in the resulting bit pattern would have evaluated to 0 and complete bit pattern would have been 00000000. Thus depending upon the bit number to be checked in the first operand we decide the second operand, and on ANDing these two operands the result decides whether the bit was ON or OFF.