(*) 2's complement - take 1 bit (the 1st one) from binary numbers to become + sign bit has 2 values: 1 (means negative) 0 (means positive) - invert all bits then +1 + ex: 7 -> 0111 -7: 1000 (1's complement - invert all bits) -> 1001 (1's complement + 1 = 2's complement) +Calculation: a-b=a+(-b) *overflow: add two operands of same sign and get result of opposite sign -detect manualy (*) Arithmetic * addition - manually check the sum to detect overflow and ignore the carry bit * subtraction - manually check the difference to detect sum (a-b=a+-b) and ignore the carry bit * multiplication by 2^n - multiples by 2 n times + multiple by 2: shift the binary number to the left and add 0 at the end * multiplication by binary - similar as multiplication of decimal numbers + multiple -> shift -> sum * mutiplication by -1 - invert a 2's complement: X -> -X-1 - add 1 to the result: -X-1+X=-1