Pointer is a variable that stores the address of another variable.
Features
- Pointer saves the memory space.
- Execution time of pointer is faster because of direct access to memory location.
- With the help of pointers, the memory is accessed efficiently, i.e., memory is allocated and deallocated dynamically.
- Pointers are used with data structures.
Pointer declaration and initialization
Consider the following statement −
int qty = 179;
In memory, the variable can be represented as follows −
Declaring a pointer
It means ‘p’ is a pointer variable, which holds the address of another integer variable, as shown below −
Int *p;
Initialization of a pointer
Address operator (&) is used to initialise a pointer variable.
For Example − int qty = 175;
int *p;
p= &qty;
Array of pointers
It is collection of addresses (or) collection of pointers
Declaration
Following is the declaration for array of pointers −
datatype *pointername [size];
For example,
int *p[5];
It represents an array of pointers that can hold 5 integer element addresses.
Initialization
‘&’ is used for initialisation.
For Example,
int a[3] = {10,20,30};
int *p[3], i;
for (i=0; i<3; i++) (or) for (i=0; i<3,i++)
p[i] = &a[i];
p[i] = a+i;Accessing
Indirection operator (*) is used for accessing.
For Example,
for (i=0, i<3; i++)
printf ("%d", *p[i]);Example program
Given below is the program for array of pointers −
#include<stdio.h>
main ( ){
int a[3] = {10,20,30};
int *p[3],i;
for (i=0; i<3; i++)
p[i] = &a[i];
printf ("elements of the array are \n");
for (i=0; i<3; i++)
printf ("%d \t", *p[i]);
}Output
When the above program is executed, it produces the following result −
elements at the array are : 10 20 30
Example 2
Given below is the program for the array of pointers to strings −
#include <stdio.h>
#include <stdlib.h>
int main(void){
char *a[5] = {"one", "two", "three", "four", "five"};
int i;
printf ( "the strings are at locations:\n");
for (i=0; i<5; i++)
printf ("%d\n", a[i]);
return 0;
}Output
When the above program is executed, it produces the following result −
The strings are at locations: 4210688 4210692 4210696 4210702 4210707