two's complement

[computerbum]

I am trying to understand what how to use two's complement.

 

If I have the number 128, I know that I can find the number by converting 128 to binary such as:

 

0000 0000 1000 0000

 

Then invert the digits like so:

 

1111 1111 0111 1111

 

Then add one to it like so:

 

1111 1111 1000 0000

 

which will give me -128

 

but what about if I want to find 2's complement of -128 would I still do it the same way as above which would give me the value of 128?

 

 

I am new at this please help?

[D H]

Try it. What does inverting the digits and adding one do to 1111 1111 1000 0000 ?

[davemattie]

@ computerbum

 

The two's complement of a negative number is always the corresponding positive value.

 

For example, inverting the bits of −5 (above) gives:

 

00000100

 

And adding one gives the final value:

 

000001012 = 5