C++: Const vs Pointer

What is the difference between const and pointer in C++?

In C++, a pointer is a variable that holds the memory address of another variable, while 'const' is a qualifier that makes a variable immutable. When you declare a pointer as 'const', it means the pointer itself cannot change the address it points to, but the value at that address can be modified.

Can you give me an example of using const with pointers?

Sure! Here's an example:

int value = 10;
int *const ptr = &value; // ptr is a constant pointer to an int
*ptr = 20; // This is allowed, value is now 20
ptr = nullptr; // This will cause a compilation error

In this case, 'ptr' cannot point to another address after initialization.

What about const pointers? How do they work?

A 'const pointer' means that the pointer itself cannot change the address it points to, but the value at that address can be modified. For example:

const int *ptr = &value; // ptr is a pointer to a const int
*ptr = 20; // This will cause a compilation error
ptr = &anotherValue; // This is allowed, ptr can point to another address

What are the practical uses of const pointers in C++?

Const pointers are useful when you want to ensure that a function does not modify the data being pointed to, while still allowing the pointer to point to different data. This is common in APIs where you want to protect the integrity of the data.