**Sign-Magnitude form:**

- MSB is used to represent sign and remaining bits are used to represent magnitude.
- ‘0’ represents +ve, ‘1’ represents –ve.
- Ex: +6 =
__0__110 (MSB is ‘0’ hence +ve ) - -6 = 1110 (MSB is ‘1’ hence –ve)

**1’s complement form:**

- Positive numbers are represented as in sign magnitude form
- Negative numbers are represented by complementing each bit in sign magnitude form except sign bit.
- Ex: +6= 0110
- -6= 1001 (in sign magnitude form -6 is 1
__110__, to get 1’s complement, complement underlined bits)

**2’s Complement form:**

- Positive numbers are represented as in sign magnitude form
- Negative numbers are represented by complementing each bit after first non-zero bit in sign magnitude form (except sign bit)
- Ex:+6=0110
- -6 = 11
__1__0(sign-magnitude form)

Underlined bit is
first non-zero bit (from right to left), up to that bit sign-magnitude form and
2’s complement form are same, remaining bits should be complemented except sign bit. Thus 1010 is
2’s complement form of -6

- 2’s complement of a number can also obtained by adding ‘1’ to the 1’s complement of the number.

**9’s complement:**

9’s complement
of a number can be obtained by subtracting each digit from 9.

Ex: 9’s
complement of 653 = 346

**10’s complement:**

10’s
complement of a number can be obtained by subtracting right most digit from 10,
and remaining digits from 9. Otherwise 10’s complement of a number can be
obtained by adding 1 to the 9’s complement of the number.

Ex: 10’s
complement of 653 is 347

__Note:__

- R’s complement of a number ‘N’ consisting of ‘n’
digits is r
^{n}-N - (R-1)’s complement of a number ‘N’ consisting of
‘n’ digits is r
^{n}-N-1

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