Pointer

 Pointers

Pointers are one of the core components of the C programming language. A pointer can be used to store the memory address of other variables, functions, or even other pointers. The use of pointers allows low-level memory access, dynamic memory allocation, and many other Functionality in C

Syntax of C Pointers

The syntax of pointers is similar to the variable declaration in C, but we use the ( * ) dereferencing operator in the pointer declaration.

datatype * ptr;

• ptr is the name of the pointer.
• datatype is the type of data it is pointing to.

How to Use Pointers?

The use of pointers in C can be divided into three steps:

1. Pointer Declaration
2. Pointer Initialization
3. Pointer Dereferencing

 1. Pointer Declaration

In pointer declaration, we only declare the pointer but do not initialize it. To declare a pointer, we use the ( * ) dereference operator before its name.

Example

int *ptr;

The pointer declared here will point to some random memory address as it is not initialized. Such pointers are called wild pointers.

2. Pointer Initialization

Pointer initialization is the process where we assign some initial value to the pointer variable. We generally use the ( &: ampersand ) addressof operator to get the memory address of a variable and then store it in the pointer variable.

Example

int var = 10;
int * ptr;
ptr = &var;

We can also declare and initialize the pointer in a single step. This method is called pointer definition as the pointer is declared and initialized at the same time.

Example

int *ptr = &var;

 3. Pointer Dereferencing

Dereferencing a pointer is the process of accessing the value stored in the memory address specified in the pointer. We use the same ( * ) dereferencing operator that we used in the pointer declaration.

Types of Pointers in C

Pointers in C can be classified into many different types based on the parameter on which we are defining their types. If we consider the type of variable stored in the memory location pointed by the pointer, then the pointers can be classified into the following types:

1. Integer Pointers

As the name suggests, these are the pointers that point to the integer values.

Syntax

int *ptr;

2. Array Pointer

Pointers and Array are closely related to each other. Even the array name is the pointer to its first element. They are also known as pointer to array We can create a pointer to an array using the given syntax.

Syntax

char *ptr = &array_name;

3. Structure Pointer

The pointer pointing to the structure type is called Structuere Pointer or Pointer to Structure. It can be declared in the same way as we declare the other primitive data types.

Syntax

struct struct_name *ptr;

4. Function Pointers

Function pointers point to the functions. They are different from the rest of the pointers in the sense that instead of pointing to the data, they point to the code. Let’s consider a function prototype – int func (int, char), the Function pointer for this function will be

Syntax

int (*ptr)(int, char);

5. Double Pointers

In C language, we can define a pointer that stores the memory address of another pointer. Such pointers are called double-pointers or pointer-to-pointer Instead of pointing to a data value, they point to another pointer.

Syntax

datatype ** pointer_name;

Size of Pointers in C

The size of the pointers in C is equal for every pointer type. The size of the pointer does not depend on the type it is pointing to. It only depends on the operating system and CPU architecture. The size of pointers in C is 

• 8 bytes for a 64-bit System
• 4 bytes for a 32-bit System

Advantages of Pointers

Following are the major advantages of pointers in C:

• Pointers are used for dynamic memory allocation and deallocation.
• An Array or a structure can be accessed efficiently with pointers
• Pointers are useful for accessing memory locations.
• Pointers are used to form complex data structures such as linked lists, graphs, trees, etc.
• Pointers reduce the length of the program and its execution time as well.

Disadvantages of Pointers

Pointers are vulnerable to errors and have following disadvantages:

• Memory corruption can occur if an incorrect value is provided to pointers.
• Pointers are a little bit complex to understand.
• Pointers are majorly responsible for memory leaks in C.
• Pointers are comparatively slower than variables in C.
• Uninitialized pointers might cause a segmentation fault.