Pointer const and Constant Pointer

A constant pointer is a pointer that cannot change the address which it stores.

 

Syntax: datatype *const pointer_name; 

Example: 

int a=10,b=20; 

int *const ptr; 

ptr=&a; 

ptr=&b; //here the address in ptr cannot be changed so not allowed .

Pointer to constant 

Address in the pointer can be changed but the value of the data element which the pointer points cannot be changed. 

Syntax: const datatype * pointer_name; 

Example: 

int a=10,b=20; 

const int *ptr=&a; 

*ptr=100; //here the value which ptr points to cannot changed so not allowed ptr=&b; //allowed

Pointers and Const 

The previous two can be combined to form a constant pointer to constant 

Syntax: const datatype *const pointer_name; Example: 

const int * const ptr; 

int a=10,b=20; 

const int * const ptr=&a; 

*ptr=100; //not allowed 

ptr=&b;//not allowed 

Here the value which ptr points to cannot be changed and also the address in ptr cannot be changed

Also Read

1. Static and Dynamic Memory Allocation
2. Memory Leak and Dangling Pointer
3. Memory Allocation for 2D Array
4. Dynamic Memory Allocation
5. Some Pointer Declaration and their Meanings
6. Function and pointers
7. Initializing Pointer to Pointer
8. Pointer to Pointer Multiple Indirection
9. Relationship between Arrays and Pointers
10. Pointer to Array
11. Pointer Arithmetic
12. Types of Pointers
13. Illustrate Basic Pointer Use
14. Using Pointer
15. Intializing Pointer
16. Declaring Pointer
17. Application of Pointers
18. Value Model VS Reference Model
19. What is Pointer