C Preprocessor Question and Answer for Interview
1. What is a macro, and how do you use it? A macro is a preprocessor directive that provides a mechanism for token replacement in your source code. Macros are created by using the #define statement. Here is an example of a macro: #define VERSION_STAMP "1.02" The macro being defined in this example is commonly referred to as a symbol. The symbol VERSION_STAMP is simply a physical representation of the string "1.02". When the preprocessor is invoked, every occurrence of the VERSION_STAMP symbol is replaced with the literal string "1.02". Here is another example of a macro: #define CUBE(x) ((x) * (x) * (x)) The macro being defined here is named CUBE, and it takes one argument, x. The rest of the code on the line represents the body of the CUBE macro. Thus, the simplistic macro CUBE(x) will represent the more complex expression ((x) * (x) * (x)). When the preprocessor is invoked, every instance of the macro CUBE(x) in your program is replaced with the code ((x) * (x) * (x)).
