1. Identifiers may only include the following characters: letters ('a'..'z', 'A'..'Z'), digits ('0'..'9') and underscores ('_'). C is case sensitive, so seaside, SeaSide and SEASIDE are distinct identifiers.
2. The first character must not be a digit.
3. The identifier must not be one of C's 32 keywords.
auto break case char const continue default do double else enum extern float for goto if int long register return short signed sizeof static struct switch typedef union unsigned void volatile while David C. Hamill D.Hamill@surrey.ac.uk