2's complement

Discussion in 'Homework Help' started by jstrike21, Mar 2, 2010.

  1. jstrike21

    Thread Starter Member

    Sep 24, 2009
    I am supposed to find the decimal equivalent of 101110 in sign and magnitude, 1's complement, and 2's complement.

    A.) Sign and magnitude
    I have it as -(8+4+2)=-14
    B.)1's compliment
    it starts with a one so it is negative then I flip the digits so:
    negative of 10001
    C.)2's complement
    Add 1 to the absolute value of the 1s complement then make it negative so:

    Can I get some verification on this?
    Last edited: Mar 2, 2010
  2. paone

    New Member

    Dec 12, 2009
    your number is 101110(-12)
    for signed magnitude conversion in 1's and 2's comp first assume it as +12 =001110
    then for 1's comp you have to change 1's to 0's and 0's to 1's including the sign bit.
    therfore -12 in signed 1's comp equals to 110001
    and -12 in 2's comp add 1 in lsb to 1's comp
    decimal equivalent is easy you know.
  3. jstrike21

    Thread Starter Member

    Sep 24, 2009
    for sign magnitude why isn't it:
    the first 1 means negative, then after that you are left with the 5bit number 01110 which is equal to 14, then put them together to get -14?
  4. AlexR

    Well-Known Member

    Jan 16, 2008
    You are indeed correct, one's compliment of a number is simply the bit-wise not of the number so 101110 becomes -010001 = -17

    Two's complement is the bit-wise not plus 1 so 101110 becomes 010001 + 000001 = 010010 = -18

    The number is however -14 in the "signed bit and magnitude" representation system where the msb is solely used to signify the sign of the number.
    Last edited: Mar 2, 2010