Thread: unsigned char & signed char

Ones complement = invert all the bits
Twos complement = adding 1 to the ones complement

http://www.drtak.org/teaches/ARC/cis...ok/node62.html

Example: -1's big representation in binary.
(using 4 bits)
1) look at the sign, its negitive so we know we'll have to use two's complement.
2) Get binary value of |-1| which is 0001
3) Take ones complement: 1110
4) add one to get twos complement 1110 + 1 = 1111

there you have it

proof: -1 to 1 == 0

Code:

 1111
+   1
_____
10000

Now there is a rule when dealing with binary numbers. You always take the least signifiant bits. In this case we are only looking at 4 bits so the 1 gets thrown away and we are left with 0000 == 0

not quite.

1110 is the ones complement of 1

Negitive numbers can not be held in binary (there is no negitive / positive sign). As such the system of two's complement was developed.

Read the links, they explain a lot