Dereference Pointer in C

Dereferencing is, use of a pointer to access the value whose address is being stored. We use the * operator to get the value of the variable from its address.

• Note that we use * for two different purposes in pointers. One is to declare a pointer variable and the other is dereference operator.
• When we dereference a pointer, we deal with the actual data stored in the memory location it points to.
• When we write *ptr, the compiler looks at the address stored in the pointer, goes to that memory location, and accesses or changes the actual data stored there not a copy.

The address is : 0x7ffd3a5d27e4
Updated value is 10
Further updated value is 20
The value is 30

Consider the above examples where ptr points to num, the content in the memory address can be accessed by the dereferencing operator *. Now, the *ptr will fetch the content stored in the address which is 10.

Changing the value of the Pointer

There are 2 methods to change the value of pointers 

Change the address of the stored variable

One of the functionalities of the pointer is that it can store some other variable address. If we want to change the address to another variable in that case we can just reference the variable to another variable.

The address where a is stored is: 0x7ffc396e2838
The value stored at that address is: 10
Pointer is now pointing at: 0x7ffc396e283c
New value the pointer is pointing to is: 20

Change the value in the stored variable

In a few conditions, we can change the value of the actual variable when we need it rather than referencing another variable. In this, case we can just the dereferenced value to make actual changes.

The address where a is stored is: 0x7ffd32537efc
The value stored at the address by dereferencing the pointer is: 5
Pointer is still pointing at: 0x7ffd32537efc
The new value stored at the address by ...

Using Array with Pointers

An array is the collection of elements with similar data types, also the memory blocks where elements are continuous. We can use ptr to point to the elements of the array. Let's check how:

Elements of array: 1 2 3 4 5 

Dereferencing Double Pointer

The double pointers can also be dereferenced using the same logic but you will have to use the indirection operator two times: One for moving to the pointer the double pointer is pointing to and the other for accessing the actual value.