C Macros

C macro is a piece of code of the program, that has a specific name called as the macro name. If the macro name is used, then C preprocessor will be replaced with the body of the macro. C program allows us to define a macro for any valid identifier, even for C keyword.

There are two kinds of C macros, which are

• object-like macros and
• function-like macros.

Object-like macros

Object-Like macros are identifiers which will be replaced by a sequence of the piece of code in the C program and its name implied. Object-like macro is used to give a meaningful name to a constant.

In order to define a new macro in C program, we use the #define directive.

Syntax:

#define macro_name macro_body

Example:

#define pi 3.14

Function-like macros

It also allows us to define a macro that looks like a function call, which means that these macros are referred to as function-like macros.

This syntax is similar to an object-like macro, except we have to put the parentheses ( ) right after the macro name. Which is,

Syntax:

#define macro_name macro_body ( )

Example:

#include <stdio.h>

void main(){    
   printf("Date :%s\n", __DATE__ );    
   printf("Time :%s\n", __TIME__ );    
 }