Pointer in C Programming

Pointer

A pointer is a special variable that stores the memory address of another variable.

Unlike a normal variable that stores a value directly, a pointer stores the address where another variable is located in memory.

A pointer must also be declared before it can be used in a C program.

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Example

Suppose we declare an integer variable:

int a;

To store the address of a, we need an integer pointer:

int *p;

Here:

• a is an integer variable.
• p is an integer pointer variable.
• p can store the memory address of an integer variable such as a.

For example:

p = &a;

The pointer should generally be declared with a type compatible with the variable whose address it stores.

For example:

int *p;
float *f;
char *c;

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Address Operator (&)

The address operator (&) is a unary operator used to obtain the memory address of a variable.

Syntax

&variable_name

Example

int a = 10;

printf("%p", (void *)&a);

Here:

&a

represents the memory address of variable a.

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Declaration of Pointer Variable

A pointer variable is declared using the * symbol.

Syntax

data_type *pointer_variable;

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Integer Pointer

int *p;

Here, p is an integer pointer that can store the address of an integer variable.

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Character Pointer

char *c;

Here, c is a character pointer that can store the address of a character variable.

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Float Pointer

float *d;

Here, d is a float pointer that can store the address of a floating-point variable.

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Pointer Initialization

Pointer initialization means assigning the address of a variable to a pointer.

Syntax

pointer_variable = &normal_variable;

Example

int a = 57;
int *p;

p = &a;

Here:

• a contains the value 57.
• &a represents the address of a.
• p stores the address of a.

Therefore:

p = &a;

means that pointer p points to variable a.

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Referencing a Pointer

Referencing refers to making a pointer point to another variable by assigning the address of that variable to the pointer.

Example

int a = 57;
int *p;

p = &a;

Here:

&a

gives the address of a, and:

p = &a;

stores that address inside pointer p.

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Dereferencing a Pointer

Dereferencing is the process of accessing the value stored at the memory address held by a pointer.

The * operator is used for dereferencing.

Syntax

*pointer_variable

Example

int a = 20;
int *p;

p = &a;

Here:

*p

returns the value stored in a.

Therefore:

a = 20
*p = 20

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Difference Between & and *

Operator	Meaning	Example
&	Returns the address of a variable	&a
*	Returns the value stored at the address held by a pointer	*p

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Example Program of Pointer

#include <stdio.h>

int main(void)
{
    int a = 20;
    int *p;

    p = &a;

    printf("Address of a: %p\n", (void *)&a);
    printf("Value stored in p: %p\n", (void *)p);
    printf("Value of a: %d\n", a);
    printf("Value pointed to by p: %d\n", *p);

    return 0;
}

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Explanation

Consider:

int a = 20;

Variable a contains:

20

Now:

int *p;

declares an integer pointer.

When we write:

p = &a;

the address of a is stored in p.

Therefore:

a     → Value of a
&a    → Address of a
p     → Address stored in pointer p
*p    → Value stored at the address pointed to by p

Since p points to a:

*p = a

and both give:

20

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Simple Pointer Representation

Variable a
┌─────────────┐
│     20      │
└─────────────┘
      ↑
      │
      │ points to
      │
Pointer p
┌─────────────┐
│ Address of a│
└─────────────┘

So:

p = &a;

and:

*p

gives the value of a.

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Quick Revision

Pointer

A pointer is a special variable that stores the memory address of another variable.

Example

int *p;

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Address Operator

The & operator gives the address of a variable.

&a

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Pointer Initialization

int a = 57;
int *p;

p = &a;

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Dereferencing

The * operator is used to access the value stored at the address held by a pointer.

*p

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Important Example

int a = 20;
int *p;

p = &a;

Then:

a  = 20
*p = 20

while both:

&a
p

represent the address of a.

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Important Exam Points

• A pointer stores the memory address of another variable.
• A pointer is declared using the * symbol.
• int *p; declares an integer pointer.
• char *p; declares a character pointer.
• float *p; declares a floating-point pointer.
• The & operator returns the address of a variable.
• p = &a; makes pointer p point to variable a.
• The * operator is used to dereference a pointer.
• If p points to a, then *p gives the value stored in a.
• p stores an address, while *p accesses the value at that address.

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Advantages of Pointer

The provided source introduces “Advantages of Pointer” but does not include the individual advantage points.