A preprocessor directive is a message from programmer to the preprocessor.

More Questions from C Preprocessor

• Preprocessor directive #ifdef .. #else ... #endif is used for conditional compilation.
• Macro calls and function calls work exactly similarly.
• If the file to be included doesn't exist, the preprocessor flashes an error message.
• Preprocessor directive #undef can be used only on a macro that has been #define earlier
• Once preprocessing is over and the program is sent for the compilation the macros are removed from the expanded source code.
• Every C program will contain at least one preprocessor directive.
• A header file contains macros, structure declaration and function prototypes.
• In a macro call the control is passed to the macro.
• A preprocessor directive is a message from compiler to a linker.
• A macro must always be defined in capital letters.

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