Why is signed char min -128 and not -127?

Question

Singed numbers in memory are represented in such a way that the first bit defines a sign. I've taken a char as an example (and as a simpliest type to type), but this concerns other signed datatypes as well.

14 = 00001110

Since the first number is positive, the first bit is 0. The max signed char is represented like this:

127 = 01111111

It seems to be reasonable to simply change the first bit to make it negative, but then the other 7 bits still can only represent the number of 127 (if do not take the first bit into account). How then is it possible to store -128?

The limits have been taken from C library, but generally that is about basics (informatics and all that stuff), not about the language itself — Kaiyaha, Jul 22 '20 at 20:14
Does this answer your question? [What is “2's Complement”?](https://stackoverflow.com/questions/1049722/what-is-2s-complement) — mkrieger1, Jul 22 '20 at 22:39

score 2 · Accepted Answer · answered Jul 22 '20 at 20:10

2

-128 would be represented as 10000000 (which looks like -0, but that would be a redundant way of representing 0).

answered Jul 22 '20 at 20:10

Scott Hunter

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Why is signed char min -128 and not -127?

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