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C program to display relation between pointer to pointer
In C programming language, pointer to pointer or double pointer is a variable that holds the address of another pointer.
Declaration
Given below is the declaration for pointer to pointer −
datatype ** pointer_name;
For example, int **p;
Here, p is a pointer to pointer.
Initialization
‘&’ is used for initialization.
For example,
int a = 10; int *p; int **q; p = &a;
Accessing
Indirection operator (*) is used for accessing
Sample program
Following is the C program for double pointer −
#include<stdio.h>
main ( ){
int a = 10;
int *p;
int **q;
p = &a;
q = &p;
printf("a =%d ",a);
printf(" a value through pointer = %d", *p);
printf(" a value through pointer to pointer = %d", **q);
}Output
When the above program is executed, it produces the following result −
a=10 a value through pointer = 10 a value through pointer to pointer = 10
Example
Now, consider another C program which shows the relationship between pointer to pointer.
#include<stdio.h>
void main(){
//Declaring variables and pointers//
int a=10;
int *p;
p=&a;
int **q;
q=&p;
//Printing required O/p//
printf("Value of a is %d
",a);//10//
printf("Address location of a is %d
",p);//address of a//
printf("Value of p which is address location of a is %d
",*p);//10//
printf("Address location of p is %d
",q);//address of p//
printf("Value at address location q(which is address location of p) is %d
",*q);//address of a//
printf("Value at address location p(which is address location of a) is %d
",**q);//10//
}Output
When the above program is executed, it produces the following result −
Value of a is 10 Address location of a is 6422036 Value of p which is address location of a is 10 Address location of p is 6422024 Value at address location q(which is address location of p) is 6422036 Value at address location p(which is address location of a) is 10
Updated on: 11-Mar-2021
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