The C Preprocessor

You can think of the C preprocessor as a separate program that runs before the compiler, with its own simple, line-oriented grammar and syntax. In previous chapters, we introduced two preprocessor directives—the #define command for naming a constant and the #include command for including additional source files. This chapter discusses both of these directives in greater detail and also describes other preprocessor directives that have not been mentioned yet. Briefly, the preprocessor gives you the following capabilities: Macro processing.Inclusion of additional C source files.“Conditional compilation,” which enables you to conditionally compile sections of C source contingent on the value of an arithmetic expression.