Because of the sign bit, there are 2 representations for 0. This is a problem for hardware. . . The computer must do all calculations such that they come out correctly and the same whichever representation is used. Historically important, and we use this representation to get 2's complement integers. Now, nobody builds machines that are based on 1's comp.
Positive integers use the same representation as unsigned.
11100 this must be a negative number. A variation on 1's complement that does not have 2 representations for 0. How to get an integer in 2's comp. To get the additive inverse of a 2's comp integer, 1. take the 1's comp. All other remaining bits are the same as before.