The utilization of pointers and the const qualifier in C++ constitutes a fundamental aspect of memory handling and code reliability. While pointers enable programmers to directly manipulate memory locations, they also create challenges related to data alteration. Therefore, it is crucial to understand the distinctions between the different types of pointers. In this piece, we will explore the differences among const int*, const int * const, and int * const.

Table of Contents:

• What are const int*, const int * const, and int * const in C++?
• Differences among const int*, const int * const, and int * const in C++
  • const int* (Pointer to Constant Integer)
  • const int* const (Constant Pointer to Constant Integer)
  • int* const (Constant Pointer to Integer)
  • const int* vs const int * const vs int * const
• Conclusion

What are const int*, const int * const, and int * const in C++?

In C++, there exist three variants of pointers: const int*, const int* const, and int* const. These variants apply the const keyword in a unique manner compared to the modifiers that may be used on a pointer or the elements of an array that the referenced pointer points to.

Differences among const int*, const int * const, and int * const in C++

In C++, const int*, const int* const, and int* const signify different pointer types, each with distinct restrictions regarding mutability. The primary differences are based on whether it is permissible to modify the pointer itself or the value it references. Below, the key distinctions between these pointer types can be found.

1. const int* (Pointer to Constant Integer)

A const int* denotes a pointer that targets a constant integer, thereby prohibiting changes to the integer value being referenced through that pointer. Nonetheless, the pointer can be directed to a different memory location.

Characteristics:

• The pointer is mutable, which means it can be linked to another variable.
• The value remains unalterable (the integer cannot be modified via this pointer).

Example:

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Output:




The
This code demonstrates the utilization of a const int* pointer that references an integer, permitting the pointer to be redirected to a different integer while prohibiting alterations to the integer value it refers to.



2. const int* const (Unchanging Pointer to Unchanging Integer)

A const int* const signifies a fixed pointer to a fixed integer, indicating that neither the pointer nor the value it references can be altered.

Characteristics:

• The pointer remains unchanged, thus it must consistently refer to the same variable.
• The value is immutable (read-only access to the integer).

Illustration:

Result:

The code illustrates how a const int* const pointer is established that consistently references an integer while disallowing modification of the pointer or the integer’s value.

3. int* const (Fixed Pointer to Integer)

An int* const is a fixed pointer to an integer, which signifies that the pointer must continually refer to the same memory location, but the value it references may be altered.

Characteristics:

• The pointer remains unchanged, hence it must consistently reference the same variable.
• The value can be altered (modifiable through the pointer).

Illustration:

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Output:



The code demonstrates how to utilize an int* const pointer that enables alteration of the value of the targeted integer’s content while ensuring the pointer itself remains steadily directed at the same address.

const int* vs const int * const vs int * const





Pointer Category

Value Modification Permission
Pointer Reassignment Permission
Must be Initialized at Declaration?


const int*
Not Permitted
Permitted
No


const int* const
Not Permitted
Not Permitted
Yes


int* const
Permitted
Not Permitted
Yes





Conclusion
It is crucial to comprehend that utilizing these types of pointers leads to variations in memory management and code integrity within the C++ programming language. Each pointer type has its specific endpoint, characteristics, and capability to modify, determined by the data it references. When applied correctly, pointer types can prevent unnecessary immutability, safeguard against unintentional alterations, and enhance code clarity and dependability.
Differences between const int*, const int * const, and int * const – FAQs


							

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