A good answer might be:

       128  =  1000 0000

   reflect  =  0111 1111

   add one  =  1000 0000   ??????

Range of Integers with 2's Complement

Range of N Bit 2's Complement
-(2(n-1))  ... 0 ... 2(n-1) - 1

eg n= 8

-(2(8-1)) = -128  ... 0 ... 2(8-1) - 1 = 127

This is not good. A non-zero integer and its negative can't both be represented by the same pattern. So +128 can not be repd in eight bits. The maximum positive integer that can be repd in eight bits is 12710. The negative integers   -1 .. -12710  also can be represented.

What number is represented by 1000 0000? Add the repn of 12710 to it: 


   1000 0000    = ?
   0111 1111    = 12710
   ---------      
   1111 1111    =  -110

A good choice for ? is -12810. Therefore 1000 0000 represents -12810. Eight bits can represent the numbers  -12810 ... 0 ... +12710. 

QUESTION 20:

How many integers are there in the range  -12810 ... 0 ... +12710. 

How bit patterns can be formed with 8 bits?