4.3.1 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.