The value of the pointer address is constant that means we cannot change the value of the address that is pointed by the pointer.
A constant pointer is declared as follows −
Data_Type const* Pointer_Name;
For example, int const *p// pointer to const integer
Example
Following is the C program to illustrate a pointer to a constant −
#include<stdio.h>
int main(void){
int var1 = 100;
// pointer to constant integer
const int* ptr = &var1;
//try to modify the value of pointed address
*ptr = 10;
printf("%d\n", *ptr);
return 0;
}Output
When the above program is executed, it produces the following result −
Display error, trying to change the value of pointer to constant integer
Example
Following C program demonstrates what happens if we remove const −
#include<stdio.h>
int main(void){
int var1 = 100;
// removed the pointer to constant integer
int* ptr = &var1;
//try to modify the value of pointed address
*ptr = 10;
printf("%d\n", *ptr);
return 0;
}Output
When the above program is executed, it produces the following result −
10