# C Macros

C Macros:

A macro value in C replaces a part of a program with a value already defined by #define directive.

Macros can be of four types:

Object-like Macros:

When a macro is simply replaced by a value, then it is called as Object like Macro.

Syntax:

#define macro_Name macro_Value

Function-like Macros:

When a macro is replaced by a logic, same as in a function, then it is called as Function like Macro.

Syntax:

#define macro_Name macro_Logic

User Defined Macros:

Macros defined in a C program by the user, which are not defined in the C library are called as user defined Macros.

 MACRO USES _DATE_ To get current date. _TIME_ To get current time. _FILE_ To get current file. _LINE_ To get current line number. _STDC_ 1

Predefined Macros:

Some macros are already defined in the C library, these macros are called as Predefined Macros.

Example:

#include<stdio.h> #define PI 3.14 void main() { printf("PI :%f\n",PI ); printf("Date :%s\n", __DATE__ ); printf("Time :%s\n", __TIME__ ); printf("Line :%d\n", __LINE__ ); printf("STDC :%d\n", __STDC__ ); return 0; }

Output

PI :3.140000 Date :Sep 19 2018 Time :11:43:00 Line :8 STDC :1