Rules for binary addition. 0 + 0 = 0 0 + 1 = 1 + 0 = 1 1 + 1 = 10 i.e., 1 + 1 equals 0 with a carry of 1 to next higher column. 1 + 1 + 1 = 11 i.e., 1 + 1 + 1 equals 1 with a carry of 1 to next higher column.