rules of range extension for 2 complement numbers for positive and negative code example

Example: 2's complement range of numbers explained

128  =  1000 0000

   reflect  =  0111 1111

   add one  =  1000 0000   ??????

 +128 and - 128 are represented by the same pattern.
 A non-zero integer and its negative can't both be represented by the same pattern.
 So +128 can not be represented in eight bits.
 The maximum positive integer that can be represented in eight bits is 127.