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Introducation to Pointer DataStructure, C Programming

 Pointer is a special type of variable that is used to store the memory address of another variable of free memory requested by the programmer or user during the execution of  the program. To understand dynamic data structures understanding pointer is definitely must. In simple words pointer is a variable that stores memory address whereas simple variables store data.

              For example, when variable is declared the memory is allocated to that variable by the compiler during the compilation of the program. Once memory is allocated the data can be stored in that memory location. The data is referred by the name of the variable. If the address of that variable is to be stored then the pointer variable is necessary. Consider the declaration statement of “C” language: int age;

            Assuming that during compilation memory address allocated variable age is 1000, and the address 1000 is to be stored in another variable that variable should be of the type pointer.
           In case of ‘C’ language the pointer variables are simply declared by means of prefixing an asterisk (*) to the variable name in a normal declaration statement. For example, int *page; declares a pointer variable page of the type int. Now page can be used to store the address of a simple integer variable. i.e. page = &age.
            When a pointer variable is declared, the memory is not allocated to such variable during the compilation. So it can point to any already allocated address of variable or an address of requested free memory. The type of free memory or variable should match with the type of pointer variable. Pointer variables are advantageous when they are used for dynamic memory allocation and function call by reference.

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Binary Search Linear Search Works only on sorted items. such as  1,2,3,4,5,6  etc
Works on sorted as well as unsorted items. 12,4,5,3,2,1 etc Very efficient if the items are sorted Very efficient if the items are less and present in the beginning of the list. such as Suppose your list items are : 12,3,4,5,1 and you want to search 12 number then you get beginning in the list. Works well with arrays and not on linked lists. Works with arrays and linked lists.
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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 …