i am having trouble to understand complement..

i am having trouble to understand the meaning
of complement 1 and complement 2 of a certain number

after looking a this table:**broken link removed**

i came to the conclution that the complement 1 and complement 2 of a positive stays the same
but in the case of a negative number
there is a unique transformation for each type
of complement.

how does the complement to 1 and the complement to 2
changes the value of a negative number

and why it doesnt change possitive numbers

Twos compliment subtracts the number from zero and so the top bit gets set. To obtain a twos compliment number you invert all the bits and add 1 to the result. So, 1 (00000001) gets inverted (11111110) and then incremented (11111111) to get -1. Also, -1 (11111111) gets inverted (00000000) and then incremented to get (00000001) 1.

Ones compliment is the same except you don't do the increment after the inversion. So, -1 = 11111110.

In both systems the largest positive number is 127.

Check wikipedia for a longer explanation.

Mike.

i was told some thing else..

is it ok???


" Ones complement and twos complement are methods of representing negative numbers. Therefore, they don't affect positive numbers.

To represent a negative number in ones complement, the positive value simply has all its bits inverted. Example: to represent -25 in ones complement, take the binary representation of +25 which is 00011001, then invert the bits: 11100110. Done.

To represent a negative number in twos complement, take the ones complement from the previous example, and add one to it: 11100110 + 00000001 = 11100111
"