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.
#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.
#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