twos complement

data A system used in some computers to represent negative

numbers in binary. Each bit of the number is inverted

(zeros are replaced with ones and vice versa), as for onescomplement, but then one (000...0001) is added (ignoring

overflow). This avoids the two representations for zero found

in ones complement by using all ones to represent -1.

...

000...00011 = +3

000...00010 = +2

000...00001 = +1

000...00000 = 0

111...11111 = -1

111...11110 = -2

111...11101 = -3

...

This representation simplifies the logic required for addition

and subtraction, at the expense of a little extra complexity

for negation.

(1994-10-31)