assembly negtive number

Question

In assembly if i create a variable a
a DB 200
a stores 200 which is 1100 1000 in binary which is 200 or - 56 in decimal.
Can someone explain how do i get -56

Answer 1

There are different ways to deal with negative numbers.

One way is the so called 2's complement.

You have -56.
56 in binary is 00111000
Now invert the digits (0 gets 1 and 1 gets 0): 11000111
Add 1 to the number: 11001000

So -56 = 1100 1000

I think this page explains it very good: https://ryanstutorials.net/binary-tutorial/binary-negative-numbers.php