Keywords:
Keywords have fixed meanings and these meanings can not be changed. There are 32 keywords. Some compiler may use additional keywords that must be identified from the C manual. Keywords serve as basic building block for a program statement.
Such as, auto, break, double etc. All keyword must be written in lowercase.Identifiers:
The names of variables, functions and arrays are identifiers. These are user-defined names and consist of a sequence of letters and digits. Such as, my_num, _ton etc.
Rules for identifier:
- Must consist of only letters, digits and underscores.
- First character must be an alphabet or underscore.
- Only first 31 characters are significant.
- Can not use a keyword.
- Must not contain white spaces.