It is a variable which is used to store the address of another variable.
Pointer Syntax
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Example
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Details
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| int *ptr;
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pointer to an integer
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| float *ptr;
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float
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| double *ptr;
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double
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| char *ptr;
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char
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Pointers Operators
| Pointers Operators
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Pointers Operators Symbols
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Used to
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| Address Operator
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&
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Address of Operator with %u or %p formats
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| indirection Operator
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*
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Value at Address
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Sample Program on pointers.
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Output
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#include <stdio.h>
void main ()
{
int a = 20; //variable declaration
int *ptr;
// pointer variable declaration
ptr = &a;
// Variable Address stored in pointer variable
printf("variable Address a: %p\n", &a );
// address stored in pointer variable
printf("Address stored in ptr variable: %p\n", ptr );
// access the value using the pointer
printf("Value of var variable: %d\n", *ptr );
}
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variable Address a: 0x7ffd0f850424
Address stored in ptr variable: 0x7ffd0f850424
Value of var variable: 20
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| Program on
Pointers
as arguments to functions
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Output
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#include<stdio.h>
int addnos(int *a, int *b);
void main()
{
int a=10, b=10;
printf("a value = %d\n",a);
printf("b value = %d\n",b);
printf("sum = %d",addnos(&a,&b));
}
int addnos(int *a, int *b)
{
return (*a + *b);
}
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a value = 10
b value = 10
sum = 20
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Pointer to pointer
Pointer which points to the address of another pointer is known as pointer to pointer.
Pointer to pointer Syntax
int **pr;
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Sample Program for pointer to pointer.
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Output
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#include <stdio.h>
void main()
{
int n=10;
int *ptr1;
//Pointer for num
int **ptr2; //pointer to pointer
ptr2 =&ptr1;
ptr1= &n;
ptr2= &ptr1;
printf("\n n Value : %d", n);
printf("\n ptr1 Value : %d", *ptr1);
printf("\n ptr2 Value : %d", **ptr2);
/*Possible ways to find address of num*/
printf("\n Number Address : %u", &n);
printf("\n ptr1 Address : %u", &ptr1);
printf("\n ptr2 Address : %u", &ptr2);
}
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n Value : 10
ptr1 Value : 10
ptr2 Value : 10
Number Address : 1849661948
ptr1 Address : 1849661952
ptr2 Address : 1849661960
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Explanation
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Variable= value
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Variable Address
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| N=10
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&n=1849661948
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*Ptr1=10
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&ptr1=1849661952
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**Ptr2=10
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&ptr2=1849661960
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Arrays and pointers
Array name is used as a base address of the array / first element address and we assign array address into a pointer to do our required operation.
Let us take Array name = a
Int a [5] ={10, 20, 30, 40, 50};
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Array
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a[0]
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a[1]
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a[2]
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a[3]
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a[4]
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Addresses
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1005
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1007
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1009
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1011
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1013
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Elements
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10
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20
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30
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40
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50
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Int occupies 2bytes of memories.
int *ptr; //pointer to an integer
ptr =&a[0]; // ptr = contains address of a[0] base address
| Programto find
the sum of all elements of an array.
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Output
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#include<stdio.h>
void main()
{
int a[5],*ptr,i,n=5,sum=0;
ptr =a;
printf("Enter 5 Numbers\n");
for(i=0;i<n;i++)
scanf("%d", ptr +i);
for(i=0;i<n;i++)
sum=sum+(*(ptr +i));
printf("\nsum= %d",sum);
}
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Enter 5 Numbers
1
2
3
4
5
sum=15
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Array of pointers
It means we assign array addresses to the pointers.
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Sample Program
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Output
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#include <stdio.h>
void main ()
{
int a[] = {1, 2, 3};
int i, *ptr[3];
for ( i = 0; i < 3; i++)
ptr[i] = &a[i];
//assign array address to pointer
for ( i = 0; i < 3; i++)
printf("Array Element Value a[%d] = %d\n", i,
*ptr[i] );
}
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Array Element Value a[0] = 1
Array Element Value a[1] = 2
Array Element Value a[2] = 3
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Note
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S. No
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Operations on pointers
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Example
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| 1
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Pointer variables can be used for Pointer
arithmetic
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*ptr1 + *ptr2
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| 2
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Pointer variables can be used for Pointer comparison
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If(*ptr1 + *ptr2)
Statement1
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