5.3.1 Identifiers

Identifiers are used to represent C objects and functions and must conform to strict rules.

A C identifier is a sequence of letters and digits where the underscore character “_” counts as a letter. Identifiers cannot start with a digit. Although they can start with an underscore, such identifiers are reserved for the compiler’s use and should not be defined by C source code in your programs. Such is not the case for assembly-domain identifiers.

Identifiers are case sensitive, so main is different to Main.

Up to 255 characters are significant in an identifier. If two identifiers differ only after the maximum number of significant characters, then the compiler will consider them to be the same symbol.