Explain About Constant Pointer and Pointer to Constant

1. constant pointer :-

Constant Pointer mean we can't change the address of Pointer but we can change the value.That is Pointer is pointing to constant address.

 Syntax:-

int* const ptr

#include<stdio.h> int  main() {     int num=10;     int* const ptr = &num;    int *anotherptr;    int number=1000;    printf("The before num value is:%d\n",*ptr);   *ptr = number;    //ptr=anotherptr; because we can't change the address of ptr    printf("The num after value is:%d\n",*ptr);   return(0); }

2.pointer to constant :-

 Pointer to Constant means we can't change the value but we can change the address of Pointer. That is value is constant.

Syntax:-

const int *ptr;

#include<stdio.h>     int  main() {      int num=3;     const int *ptr = &num;     int *AnotherPtr;     int a=1000;     Anotherptr=&a;     printf("Before:The num value is:%d\n",*ptr);    //*ptr = 5; we can't change the value because it's const     ptr=Anotherptr;     printf("After :The num value is:%d\n",*ptr);    return(0); }

Posted in: C faq