In a C source program, the basic element recognized by the compiler is the "token." A token is source-program text that the compiler doesn't break down into component elements.

token:
 keyword
 identifier
 constant
 string-literal
 operator
 punctuator

The keywords, identifiers, constants, string literals, and operators described in this section are examples of tokens. Punctuation characters such as brackets ([ ]), braces ({ }), parentheses ( ( ) ), and commas (,) are also tokens.

Elements of C