Pointers
A
pointer is a variable that contains the address of another variable. It is a
derived data type.
Pointers
are the most powerful features of language.
A
pointer can also be used to refer to another pointer function. The purpose of
pointer is to save memory space and achieve faster execution time.
A
pointer must be of same type of variable whose address is stored in it.
·
If variable is of integer type the pointer must be
integer.
·
If variable is float type the pointer must be float
·
If variable is char type the pointer must be char.
A
pointer can contain the address of any basic data type, of array, structures,
unions etc.
Pointers
contain addresses not value.
Advantages:
1.
Pointers allow, return more than one value from a function.
2.
We can allocate or reallocate space in memory by using pointers.
3.
It allows passing of arrays and strings to functions.
4.
Pointers are used to implement several data structures like Stacks, Queues, and
Linked lists.
5. With the use of pointers program execution
becomes faster.
6.
Using pointers, arrays and structures can be handled in more efficient
way.
How to get the address of a variable?
We
can get the address of any variable using a unary operator called Address
of operator &. As the
address of any variable is a positive number, the format specifies %u or %p or
%x is used while printing the address. %u prints the address in decimal, %p and
%x print the addresses in hexadecimal.
Address operator: & is known as
address operator, The address operator returns the address of a variable.It is
an unary operator.
Example:
WAP to show the use of "address of operator “
#include<stdio.h>
#include
<conio.h>
void
main()
{
int
var=100;
clrscr();
printf(“the
address of var is %u”,&var);
getch();
}
Declaring pointer variables:
Like
other variables in C, a pointer variable has to be declared before it can be
used in the program.
Syntax: data type *
name;
Where
"data type" is the type of the pointer variable and "name"
is the name of the pointer variable. The asterisk Sign (*) is used to inform
the compiler that the variable being is a pointer.
Example: int *ptr;
Initialization of pointer:
Pointer will contain garbage value if we don't
initialize them. So it is necessary to initialize the pointer variables
properly. The pointer variables are initialized using address of
operator.
Example:
int a=90;
int
*ptr &a;
/*WAP using pointer*/
#include<stdıo.h>
#include<conio.h>
void
main()
{
int
x=10;
int
*ptr;
ptr
&x;
clrscr():
printf("\n
vale of x=%d",x);
printf("\n
value of ptr=%u",ptr);
printf(“\n
address of ptr=%u”,&ptr);
printf(“\n
value of ptr=%d". *ptr);
getch():
}
ACCESSING VARIABLE THROUGH ITS POINTER
After initialization pointer variable, if we
want to access the value of pointer, we have to put an asterisk ('*'
sign) character just before the pointer variable.
indirection Operator: The ‘*’ is an
indirection operator. It is a unary operator. It is used to create a pointer variable.
Indirection
operator is used to find out value.
#include<stdıo.h>
#include<conio.h>
void
main()
{
clrscr();
int num = 100;
int *ptr;
ptr
= #
printf("value
of num = %d\n", *ptr);
getch();
}
Pointer and Arrays
Pointer and array are very closely related to
each other. An array is group of elements of same type. In C the name of an
array identify as base address of the array.
Pointer and 1-D Array
The array will be stored in the contiguous
memory location. Let us consider the following array declaration:-
int ar[]={10,20,30,40,50};
|
10 |
20 |
30 |
40 |
50 |
2001 2003 2005 2007 2009
The array ar is int type, each element of
this array occupies two bytes. The name of the array contains the starting
address of the array.
Example: WAP to show the
relation between array and pointer
#include<stdio.h>
#include<conio.h>
void
main()
{
int
ar[5]={10,20,30,40,50);
int
*p,i;
p=ar;
for
(i=0;i< 5; i++)
{
printf("\n
the value stored at the location %d is %d", i,p[i]);
}
getch():
}
Output:
the
value stored at the location 0 is 10
the
value stored at the location 1 is 20
the
value stored at the location 2 is 30
the
value stored at the location 3 is 40
the
value stored at the location 4 is 50
Pointer and 2 D Array
In 2
dimensional array , another index variable j is used. Let us consider the
following array declaration:-
int ar[3][4];
·
Where ar is name of two-dimensional array of 3 rows and 4
columns.
·
E.g. int ar[3][4] can be stored in the contiguous memory
location.
To
access the elements of a 2-dim array
a[i][j]=*(*(a+i)+j)
/* WAP 2 D Array with pointer*/
#include<stdio.h>
#include<conio.h>
void
main()
{
int
ar[3][4]={
{10,20,30,40},
{5,6,7,8}, {9,10,11,12},
};
int
i,j;
clrscr();
for
(i=0;i<3;i++)
{
for(j=0;j<4;j++)
{
printf("\n
The value stored at the location[%d][%d]is %d", i, j, *(*(ar+i)
+j));
}
getch();
}
0 Comments