What is a macro in C? how to use macro?

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.


example of a macro:

Macros can also utilize special operators such as the stringizing operator (#) and the concatenation operator (##).The stringizing operator can be used to convert macro parameters to quoted strings, as in the following example:

#define DEBUG_VALUE(v) printf(#v ? is equal to %d.n?, v)

In your program, you can check the value of a variable by invoking the DEBUG_VALUE macro:

...
int x = 20;
DEBUG_VALUE(x);
...

The preceding code prints ?x is equal to 20.? on-screen. This example shows that the stringizing operator used with macros can be a very handy debugging tool.