Pointer is a variable that stores the address of another variable. The document discusses the syntax and declaration of pointers, initialization of pointers, pointer operators like * and &, void pointers, NULL pointers, pointers to pointers, and the relationship between arrays and pointers. Pointers allow accessing and modifying the value of the variable to which they point. The address of operator & returns the address of a variable, and the indirection operator * accesses the value of the variable at the address stored in the pointer.

1. Pointer
• Pointer is a variable, that stores the address of another
variable.
• Syntax:
data_type *pointer_name;
• Here, the data type specifies the type of data to which the
pointer points.
• The pointer name specifies the name of the pointer. It must
preceded with an * (Asterisk).
Examples:
• int *iptr; // iptr is pointer to an integer variable
• float *fptr; // fptr is pointer to an float variable
• char *cptr; // cptr is a pointer to a character variable

2. Initialization of a pointer variable
• The process of assigning the address of another variable to a
pointer variable is known as initialization.
• A pointer can be assigned or initialized with the address of an
variable.
• A pointer variable cannot hold a non-address value.
• A pointer can be assigned or initialized with another pointer
of the same type.
• A pointer can be assigned or initialized with another pointer
of the same type. However, it is not possible to assign a
pointer of one type to a pointer of another type without
explicit type casting.
Example:
P=&n;

3. Initialization of a pointer variable
Example:
• P=&n;
• Where, ‘p’ contains the address of variable ‘n’. The data item
represented by ‘n’ can be accessed by ‘*p’.
• Where * is called the indirection operator.
• We can initialize a pointer variable while declaring it, as
given below.
int num=15;
int *iptr=# // Initialization while declaration
• In the above example, variable num is first declared and then
its address is stored in pointer variable iptr.

4. Pointer Operators
*  Represents the value
 Also called Indirection operator / Dereferencing
operator / Value of operator.
&  It represents the address.
 Also called as, direction operator / referencing
operator / Address of operator.

7. Pointer Example
#include<stdio.h>
void main()
{
int a=10,v;
int *p;
p=&a;
v=*p;
printf("Address of a is % un", p);
printf("Value is %d", v);
}

8. Void Pointer or Generic Pointer
• A void pointer is a generic pointer. (i.e) Means it has no
associated data type.
• A void pointer that can point to any data type and is known as
void pointer.
• A void pointer can hold address of any type and can be
“typecasted” to access the values.
• Syntax:
void *pointer_name; /* pointer to void*/
Example:
int i=5;
void *vptr;
vptr=&i;
printf(“Value of vptr =%d”, *(int*)vptr);

9. NULL Pointer
• A Null pointer is a special pointer that does not point to any
memory location.
• It represents an invalid memory location.
• It does not hold the address of any variable.
• It has numeric value 0.
• When a NULL value is assigned to a pointer the pointer is
considered as NULL pointer.
Declaration:
int *nptr=NULL;
or
int *nptr=0;

10. Pointers to Pointers
• In C, a pointer stores the address of another variable which in
turn can store address of another variable and so on.
• Therefore we can have a pointer that stores another pointer’s
address.
• Example:
int val=500, *ptr, **ptr_to_ptr;
ptr=&val;
ptr_to_ptr=&ptr;
Here, *ptr denotes an integer pointer.
**ptr_to_ptr denotes a pointer to an integer pointer.
This is known as multiplication indirections.

11. Pointers to Pointers (An Example)
#include<stdio.h>
#include<conio.h>
void main()
{
int a=50;
int *b;
int **c;
clrscr();
b=&a;
c=&b;
printf("n Value of a is %d ", a);
printf("n Value of a is %d", *(&a));
printf("n Value of a is %d", *b);
printf("n Value of a is %d", **c);
printf("n Value of b and
address of a= %u", b);
printf("n Address of a is %u", &a);
printf("n Address of b is %u", &b);
printf("n Address of a is %u", *c);
printf("n Address of b is %u", &b);
printf("n Address of b is %u", c);
printf("n Address of c is %u", &c);
getch();
}
Output:
Value of a is 50
Value of a is 50
Value of a is 50
Value of a is 50
Value of b and address of a= 65524
Address of a is 65524
Address of b is 65522
Address of a is 65524
Address of b is 65522
Address of b is 65522
Address of c is 65520

12. Relationship between Arrays and
Pointers
• The following relationships exist between arrays and pointers:
1. The name of an array refers to the address of the first element of the
array, i.e. an expression of array type decomposes to pointer type.
A program to depict the relationship between arrays and pointers
#include<stdio.h>
main()
{
int arr[3]={40,15,20};
printf("First element of array is at %p
n",arr);
printf("Second element of array is at %p
n",arr+1);
printf("Third element of array is at %p
n",arr+2);
}
OUTPUT:
First element of array is at 24D7;2242
Second element of array is at 24D7:2244
Third element of array is at 241J7:2248

13. Relationship between Arrays and
Pointers
• The name of an array refers to the address of the first element
of the array but there are two exceptions to this rule:
• a. When an array name is operand of sized operator it does
not decompose to the address of its first element.

14. Relationship between Arrays and Pointers
• In C language, any operation that involves array subscripting is done
by using pointers. The expression of form E1[E2] is automatically
converted into an equivalent expression of form *(E1+E2).

15. Array of Pointers
• Array of pointers is a collection of addresses.
• The addresses in an array of pointers could be the addresses
of isolated variables or the addresses of array elements or any
other addresses.
• Example:
int *p[3];

16. Pointers to an Array
• It is possible to create a pointer that points to a complete array
instead of pointing to the individual elements of an array.
Such a pointer is known as pointer to an array
• Example:
int (*p1)[3];
int (*p2)[2][2];