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Pointer values in C language

Suppose, we have the following declaration:

int i=100, j=200, k=300;

This declaration tells the compiler to perform the following activities:

  • Reserve space for three integer values in memory.
  • Associate the variables i,j and k with these memory location.
  • Store 100,200 and 300 at the locations i,j and k respectively as shown as below:

Memory Locations





The address of the variable cannot be accessed directly. The address of the variable can be obtained using address operator (& in C) .

Note : The address operator can be used with any variable that can be placed on the left side of an assignment operator.Since constants, expressions and array names can not be used on the left hand side of the assignment, and hence accessing address is invalid for constants, expressions and array names. The following are invalid:

Reasons for invalidity
Address of a constant cannot be obtained.
Address of an expression cannot be obtained.

Address of an expression cannot be obtained.
Int a[10];
Address of entire array cannot be obtained.
Register a;
Address of a register variable cannot be obtained.

Note : if a is an array , then address of the first location of the array is obtained either using : &a[0] or a.

Assume that the compiler has chosen the address 65530 for the variable i, the address 65532 for the variable j and 65534 for the variable k. These address assigned to variables i,j and k are called pointer values.

Definition : Memory is divided into number of storage cells called locations. All the locations in computer memory are numbered sequentially from 0 to 65535 ( with memory size of 64k) . Out of these address, the system assigns some addresses of the memory locations to the variables. These memory addresses assigned to variables by the system are called pointer values. 


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Memory representation of Linked List Data Structures in C Language

Memory representation of Linked List

             In memory the linked list is stored in scattered cells (locations).The memory for each node is allocated dynamically means as and when required. So the Linked List can increase as per the user wish and the size is not fixed, it can vary.

               Suppose first node of linked list is allocated with an address 1008. Its graphical representation looks like the figure shown below:

      Suppose next node is allocated at an address 506, so the list becomes,

  Suppose next node is allocated with an address with an address 10,s the list become,

The other way to represent the linked list is as shown below:

 In the above representation the data stored in the linked list is “INDIA”, the information part of each node contains one character. The external pointer root points to first node’s address 1005. The link part of the node containing information I contains 1007, the address of next node. The last node …