#include<stdio.h>
#include<conio.h>
void main()
{
	int i, *j, **k;

    i = 10;
    j = &i;
    k = &j;

    printf("\tValues in variables\n");
    printf("Value in i %d\n",i);
    printf("Value in j (which is the address of i) %d\n",j);
    printf("Value in k (which is the address of j) %d\n",k);
    //Lets see what is the real address of i,j,k
    printf("\n\tAddresses\n");
    printf("Address of i (which is the value in j) %u\n",&i);
    printf("Address of j (which is the value in k) %u\n",&j);
    printf("Address of k %u\n",&k);

    //printing using pointer
    printf("\n\tValues using pointers\n");
    printf("Value in i %d\n",*(&i));
    printf("Value in i %d\n",*j);
    printf("Value in i %d\n",**k);
    printf("Value in j %d\n",*(&j));
    printf("Value in j %d\n",*k);
    printf("Value in k %d\n",*(&k));

    getch();
}

        Values in variables
Value in i 10
Value in j (which is the address of i) 6422300
Value in k (which is the address of j) 6422296

        Addresses
Address of i (which is the value in j) 6422300
Address of j (which is the value in k) 6422296
Address of k 6422292

        Values using pointers
Value in i 10
Value in i 10
Value in i 10
Value in j 6422300
Value in j 6422300
Value in k 6422296

Pointer Declaration
A pointer variable holds memory address of some other variable instead of holding the actual value itself.
Syntax to declare pointer variable:
<data_type> *<variable_name>;
Data type of a pointer must be same as the data type of the variable to which the pointer variable is pointing.
For example,
int *num; //pointer to integer variable
float *price; //pointer to float variable
char *ch; //pointer to character variable

Pointer Initialization
Pointer Initialization is the process of assigning address of a variable to a pointer variable. Pointer variable can only contain address of a variable of the same data type. In C language address operator & is used to determine the address of a variable. The & (immediately preceding a variable name) returns the address of the variable associated with it.

Let us understand this with the help of an example.
int i;
int *j; //pointer declaration
j = &i; //pointer initialization
Here, 'i' is a normal variable and 'j' is a pointer variable.
variable j is storing the address of variable i (j = &i;)



Using the pointer (dereferencing pointer)
Once a pointer has been assigned the address of a variable, to access the value of the variable, pointer is dereferenced, using the indirection operator or dereferencing operator *.

Let us understand this with the help of an example.
int i;
int *j; //pointer declaration
j = &i; //pointer initialization
i = 10;
printf("%d", *j); //Dereferencing operator, will print the value of i i.e. 10
To access the value of a certain address stored by a pointer variable, * is used. Here, the * can be read as 'value at'.

Pointer to a pointer
Pointers are used to store the address of other variables of similar datatype. But if you want to store the address of a pointer variable, then you again need a pointer to store it. Thus, when one pointer variable stores the address of another pointer variable, it is known as Pointer to Pointer variable or Double Pointer.

Syntax:
<data-type> **<pointer-name>
example,
int **p1;
Here, we have used two indirection operator(*) which stores and points to the address of a pointer variable i.e, int *.
If we want to store the address of this (double pointer) variable p1, then the syntax would become:
int ***p2;

Now, In the above program, a normal variable 'i', a pointer variable 'j' and a double pointer variable 'j' are declared.
int i, *j, **k;

i = 10;
j = &i;
k = &j;

Here, 'i' is a normal integer variable, which contains the value 10
'j' is a pointer variable that stores the address of a normal integer variable i.e. 'i'.
'k' is a double pointer variable that stores the address of a pointer integer variable i.e. 'j'.



printf("Value in i %d\n",i);
This statement simply prints the value of i i.e. 10.

printf("Value in j (which is the address of i) %d\n",j);
This statement prints the value in pointer variable j, which is 6422300 (address of i) as shown in the above figure.

printf("Value in k (which is the address of j) %d\n",k);
This statement prints the value in pointer variable k, which is 6422296 (address of j) clearly depicted in the above figure.


printf("Address of i (which is the value in j) %u\n",&i);
This statement prints the address of variable i, which is 6422230.

printf("Address of j (which is the value in k) %u\n",&j);
This statement prints the address of pointer variable j, which is 6422296.

printf("Address of k %u\n",&k);
This statement prints the address of pointer variable k, which is 6422292.


printf("Value in i %d\n",*(&i));



printf("Value in i %d\n",*j);



printf("Value in i %d\n",**k);



printf("Value in j %d\n",*(&j));



printf("Value in j %d\n",*k);



printf("Value in k %d\n",*(&k));