This chapter introduces the preprocessor. Preprocessing occurs before a program is compiled. Some possible actions are inclusion of other files in the file being compiled, definition of symbolic constants and macros, conditional compilation of program code and conditional execution of preprocessing directives. All preprocessing directives begin with
#, and only whitespace characters may appear before a preprocessing directive on a line. Preprocessing directives are not C++ statements, so they do not end in a semicolon (
;). Preprocessing directives are processed fully before compilation begins.
Common Programming Error E.1