Array, Pointer and Introduction to Data Structure

Pointer, Array and Introduction 

to Data Structure

  I. Array

Array is a collection of similiar data elements. The data elements in an array always have the same data type (homogenous). The elements of the array are stored in consecutive  memory locations and are referenced by an index, which starts from index 0.

• Array Declaration and Accessing Array

There are two types of array:

-One Dimensional Array

-Multi Dimensional Array

One Dimensional Array

Syntax : type name[size N];

An array of size N have indexes from 0 to N-1

Example:

Declaration:

 char arr[5];

Accessing  : 

arr[0]=H;

arr[1]=e;

arr[2]=l;

arr[3]=l;

arr[4]=o;

Multi Dimensional Array

In multi dimensional array, there is a limit of 255 indexes.

Syntax : type name[size1][size2]...[sizeN];

size1 ranged from index 0 to size-1

size2 ranged from index 0 to size-1, and so on

Example:

Declaration:

int arr[4][3][7][10];

Accessing:

arr[0][2][2][9]= 2;

arr[2][1][6][0]= 9;

arr[3][0][0][6]= 13;

arr[2][1][3][8]= 10;

       •Storing Array Values

1. Initialization

    Example : int marks[5] : {90,80,78,82,85};

2. Inputting Values

    Example : int i, marks[10];

                     for(i=0;i<10;i++){

                           scanf("%d",&marks[i]);

                     }

3. Assigning Values

    Example : int i, arr1[10], arr2[10];

                     for(i=0;i<10;i++){

                     arr2[i] = arr1[i]

                     }

     •Operations in Array

There are some operations that can be performed on arrays, such as :

-Transversal

-Insertion

-Searching

-Deletion

-Merging

-Sorting

II. Pointer

Pointer is a data type whose value refers to another value stored elsewhere in computer memory using its address.

There is two kinds of pointer, single and multiple pointer,

The single pointer is pointing towards a value using its memory address, while the multiple pointer  

is the pointer pointing the pointer before itself.

The two most important operators used with pointer type are:

• &  the address operator

• *   the dereferencing operator

Example

Declaration :

int x;           (x is an integer)

int *px;       (*px is a pointer to an integer)

If we say :

*px = &x;

That means *px returns the address value of x.

To assign the value of x we can declare:

x = 10

or

*px=10

III. Data Structure

A data structure is an arrangement of data, either in the computer’s memory or on the disk storage.

Types of Data Structure

     •Array

      A collection of similiar data elements which has a same data type

     •Linked List

      A very dynamic data structure in which the elements can be added to or deleted from anywhere

      at will

     •Queue

     A type of data structure which the element that was inserted first is the first one to be taken out.

      •Stacks

     Stacks can be represented as a linear array. Every stack has a variable TOP associated with it

      •Binary Trees

      A data structure which is defined as a collection of elements called the node

      Every node contains a left pointer, a right pointer, and a data element.

      •Data Type

       Data Type is a collection of objects and a set of operations that act on those objects.

Abstract Data Type

Abstract Data Type (ADT) is a data type that is organized in such a way that the specification of 

the objects and the specification of the operations on the objects is separated from the 

representation of the objects and the implementation of the operations.