Explain the concept of Array of Pointer and Pointer to Pointer in C programming

Array Of Pointers

Just like any other data type, we can also declare a pointer array.

Declaration

datatype *pointername [size];

For example, int *p[5]; //It represents an array of pointers that can hold 5 integer element addresses

Initialization

The ‘&’ is used for initialization

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

#include<stdio.h>
main (){
   int a[3] = {10,20,30};
   int *p[3],i;
   for (i=0; i<3; i++)
      p[i] = &a[i]; //initializing base address of array
   printf (elements of the array are”)
   for (i=0; i<3; i++)
      printf ("%d \t", *p[i]); //printing array of pointers
   getch();
}

Output

elements at the array are : 10 20 30

Pointer to Pointer

Pointer to pointer is a variable that holds the address of another pointer.

Declaration

datatype ** pointer_name;

For example, int **p; //p is a pointer to pointer

Initialization

The ‘&’ is used for initialization.

Eg −

int a = 10;
int *p;
int **q;
p = &a;

Accessing

Indirection operator (*) is used for accessing.

Example

#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

a=10
a value through pointer = 10
a value through pointer to pointer = 10