Macros in C Programming Language

Macro substitution is a mechanism that provides a string substitution. It can be achieved through "#deifne".

It is used to replace the first part with the second part of the macro definition, before the execution of the program.

The first object may be a function type or an object.

Syntax

The syntax for macros is as follows −

#define first_part second_part

Program

In the program for every occurrence of first_part is replaced with the second_part throughout the code.

 Live Demo

#include<stdio.h>
#define square(a) a*a
int main(){
int b,c;
printf("enter b element:");
scanf("%d",&b);
c=square(b);//replaces c=b*b before execution of program
printf("%d",c);
return 0;
}

Output

You will see the following output −

enter b element:4
16

Consider another program that explains the functioning of macros.

 Live Demo

#include<stdio.h>
#define equation (a*b)+c
int main(){
   int a,b,c,d;
   printf("enter a,b,c elements:");
   scanf("%d %d %d",&a,&b,&c);
   d=equation;//replaces d=(a*b)+c before execution of program
   printf("%d",d);
   return 0;
}

Output

You will see the following output −

enter a,b,c elements: 4 7 9
37