Const modifier and pointer

There are three combinations of const and pointer: pointer to constant, constant pointer, and constant pointer to constant.

 

1. pointer to a constant

Definition: const data type * pointer variable name

Meaning: A pointer variable pointing to a constant.

Note: This pointer can be changed to another constant, but the constant pointed to by this pointer cannot be changed.

Example:

Const char * name = "Chen"; // declare the pointer name pointing to a constant

Name [3] = 'a'; // error. The value of the variable pointed to by the pointer cannot be changed.

Name = "Zhang"; // valid. The value of the pointer can be changed.

 

2. Constant pointer

Definition: Data Type * const pointer variable name = initialization value

Meaning: an unchangeable pointer variable pointing to a variable.

Note: initialization is required when defining regular pointers;

The value of this pointer cannot be changed, but the value of the variable pointed to by this pointer can be changed.

Example:

Char * const name = "Chen"; // declare the constant pointer name

Name [3] = 'a'; // valid. The variable value pointed to by the pointer can be changed.

Name = "Zhang"; // error. The pointer value cannot be changed.

 

3. Constant pointer to a constant

Definition: const data type * const pointer variable name = initialization value

Meaning: a constant pointer variable pointing to a constant.

Note: The pointer must be initialized during definition;

The value of this pointer and the value of the constant it points to cannot be changed.

Example:

Const char * const name = "Chen"; // declare a constant pointer to a constant

Name [3] = 'a'; // error. The variable value pointed to by the pointer cannot be changed.

Name = "Zhang"; // error. The pointer value cannot be changed.