What is the numerical range of a char?

There is no defined range of values in C. The built-in types all have ranges that are defined in <stdint.h>, <limits.h> and <float.h>. These ranges are implementation-defined, they are not defined by the language or by the standard. The standard only defines minimum guarantees such that a char is always at least 8 bits long (CHAR_BIT) and that an int is at least as long as a short which is at least as long as a char.