Constant is a value that cannot be changed during program execution; it is fixed.
In C language, a number or character or string of characters is called a constant. And it can be any data type. Constants are also called as literals.
There are two types of constants −
Primary constants − Integer, float, and character are called as Primary constants.
Secondary constants − Array, structures, pointers, Enum, etc., called as secondary constants.
Syntax
const datatype variable;
Example for Primary constants
#include<stdio.h>
int main(){
const int height=20;
const int base=40;
float area;
area=0.5 * height*base;
printf("The area of triangle :%f", area);
return 0;
}Output
The area of triangle :400.000000
Example for secondary constants
include<stdio.h>
void main(){
int a;
int *p;
a=10;
p=&a;
printf("a=%d\n",a);//10//
printf("p=%d\n",p);//address value of p//
*p=12;
printf("a=%d\n",a);//12//
printf("p=%d\n",p);//address value of p//
}Output
a=10 p=6422036 a=12 p=6422036