the preprocessor in c The Preprocessor In C:- The C Preprocessor is not a part of the compiler, but is a separate step in the compilation process. In simple terms, a C Preprocessor is just a text substitution tool and it instructs the compiler to do required preprocessing before the actual compilation. All Preprocessor commands begin with a hash symbol (#). It must be the first nonblank character, and for readability, a preprocessor directive should begin in the first column Of Program Some Of Preprocessors Are:- #define :-Substitutes a preprocessor macro. #include :-Inserts a particular header from another file. #undef: - Undefines a preprocessor macro. #ifdef: - Returns true if this macro is defined. #ifndef :- Returns true if this macro is not defined. #if :- Tests if a compile time condition is true. #else :- The alternative for #if. #elif :- #else and #if in one statement. #endif :- Ends preprocessor conditional. #error :- Pri...