What is a macro, and how do you use it?

macro is single line code block, e.g. #define area(r) (3.1415*(r)*(r)) where ever you refer to the macro area(r), it will be replace with the actual code block defined in macro radius=10; area=area(radius); so in the above code the macro is replaced with the actual code area=(3.1415*(radius)*(radius)) read less

Gcc website says "A macro is a fragment of code which has been given a name. Whenever the name is used, it is replaced by the contents of the macro." In our terms, A macro is something prefixed by a # and used be preprocessor. There are various macros like define,ifdef,ifndef,if,include etc. Its very easy to use but you must understand when to use one. read less

Macro is a very useful construct. Basically it is a piece of code with name. Macros are declared using #Define preprocessor directive. these are used to define constants as well as functions. e.g. pi is a constant hence instead of declaring it as a variable like float pi=3.14 it can be declared as a constant like #Define pi 3.14. e.g. #Define area(l,b) (2(l+b)) whenever pi or area(l,b) will be used they will expand to 3.14 and (2(l+b)). user has to pass the appropriate value for l(length) and b(breadth) i.e. whenever the compiler find a macro name it replaces the name with its contents. A macro is accessible to all the functions of the program. e.g. if pi is defined as a variable then it will be accessible by the function where it is declared but if declared using #Define then it is accessible by all the functions of the program. read less

Macro in C is also called symbolic constant , it replaces the code part. ex:#define line "\n..................\n", ex: #define Square(x) (x)*(x), this is called function macro it will work as Square(5) = 25 but it is not type safe user may enter alphabet instead of number and progam will fail. better way is to use user defined function read less