c macros

1#define PRINT(x) std::cout << x << std::endl

1/* 
2Every time the program encounters circleArea(argument),
3it is replaced by (3.1415*(argument)*(argument)).
4*/
5#define circleArea(r) (3.1415*(r)*(r))

1A macro is defined at the top of your program.
2for eg: #define PI 3.14
3Now whenever you write PI in your program 'PI' is replaced by 3.14
4Actually this replacement is done by the preprocessor before the source code is compiled.
5