c - What does signed and unsigned values mean?

Question

What does signed mean in C? I have this table to show:

This says signed char 128 to +127. 128 is also a positive integer, so how can this be something like +128 to +127? Or do 128 and +127 have different meanings? I am referring to the book Apress Beginning C.

Answer 1

A signed integer can represent negative numbers; unsigned cannot.

Signed integers have undefined behavior if they overflow, while unsigned integers wrap around using modulo.

Note that that table is incorrect. First off, it's missing the - signs (such as -128 to +127). Second, the standard does not guarantee that those types must fall within those ranges.