Tokens and Keywords C++ Tokens A token is the smallest element of a C++ program that is meaningful to the compiler. The C++ parser recognizes these kinds of tokens: identifiers, keywords, literals, operators, punctuators, and other separators. A stream of these tokens makes up a translation unit. Tokens are usually separated by “white space.” White space can be one or more: Blanks Horizontal or vertical tabs New lines Formfeeds Comments Syntax token: keyword identifier constant operator punctuator preprocessing-token: header-name identifier pp-number character-constant string-literal operator punctuator each nonwhite-space character that cannot be one of the above The parser separates tokens from the input stream by creating the longest token possible using the input characters in a left-to-right scan. Consider this code fragment: a = i+++j; The programmer who wrote the code might have intended either of these two statements: a = i + (++j) or a = (i++) + j Because the parser creates the longest token possible from the input stream, it chooses the second interpretation, making the tokens i++, +, and j. Keywords: Keywords implement specific C++ language features. They cannot be used as names for variables or other user-defined program elements. Most of the keywords are common to both C and C++, but some are specific to C++. Computer programming languages, such as C++, reserve a set of words for use within the language. These words, which are called keywords, tell the compiler what your program is supposed to do. Keywords cannot be used for other purposes, such as variable names, tags, or function names. C++ Keywords: asm auto break case catch char class const continue default delete do double else enum extern float for friend goto if inline int long new operator private protected public register return short signed sizeof static struct switch template this throw try typedef union unsigned virtual void volatile while

C++ Tokens

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