significance of negative values of type char in C

Question

1. chars in 'C' are used to represent characters.
2. Numbers representing characters in all code pages are always positive.

What is the use of having signed characters?? Are negative values contained in chars used only as integral values in a smaller integral data-type than int and short?? Do they have no other interpretation??(like positive values in chars representing characters)

Answer 1

Only characters of the basic execution character set are guaranteed to be nonnegative (C99, 6.5.2 §3):

An object declared as type char is large enough to store any member of the basic execution character set. If a member of the basic execution character set is stored in a char object, its value is guaranteed to be nonnegative. If any other character is stored in a char object, the resulting value is implementation-defined but shall be within the range of values that can be represented in that type.

You have to discern between the 'plain' char type and the types signed char and unsigned char as well: signed char and unsigned char are ordinary integer types for which the following holds (C99, 6.5.2 §5):

An object declared as type signed char occupies the same amount of storage as a ‘‘plain’’ char object.

Answer 2

chars in 'C' are used to represent characters.

Not always, chars are used to represent bytes, they are the only type in c with a known size.