Learning the Basics of C51 3 "Keywords and Identifiers"

3 Keywords and Identifiers

    3.1 Keywords Keywords
    are words that are used by Turbo C2.0 itself and cannot be used for other purposes. For example, keywords cannot be used as variable names, function names, etc.
    Turbo C2.0 has the following keywords:
    11 keywords extended by Turbo C2.0
     asm _cs _ds _es _ss cdecl
     far near huge interrupt pascal
    32 keywords defined by ANSI standard
     auto double int struct break else
     long switch case enum register typedef
     char extern return union const float
     short unsigned continue for signed void
     default goto sizeof volatile do if
     while static

    3.2 Identifiers
    Identifiers are constants, variables, statement labels, and user-defined function names. The definition of Turbo C 2.0 identifiers is very flexible. As an identifier, it must meet
the following rules:
    1. All identifiers must start with a letter (a~z, A~Z) or an underscore (_);
    2. The rest of the identifier can be composed of letters, underscores or numbers (0~9);
    3. Uppercase and lowercase letters have different meanings, that is, they represent different identifiers;
    4. Only the first 32 characters of an identifier are valid;
    5. An identifier cannot use Turbo C2.0 keywords.
    Here are some correct and incorrect identifiers:
               Correct Incorrect
               smart 5smart
               _decision bomb?
               key_board key.board
               FLOAT float