Introduction to Data Structure

Data

Data are simply values, fact or set of values. It is represented in the form of text or number or in the form of figures, tables, graphs, pictures etc. Data can be stored in physical devices such as a memory.

Information

Meaningful or processed data is called information. Example- student’s details, payroll system, employee’s salary details, school- college information etc.

Data Structure

The data structure is an organized collection of data. It is defined as a logical or mathematical model of a particular organization of data. Abstract data type refers to the basic mathematical concepts that define the data types such as Int, Float Character etc.

The data structure also provides a method of representing logical relationships between individual data elements. It provides a convenient method to handle various data types including Abstract Data Type (ADT). Example- Arrays, Linked List, Trees, Stacks, Queues, Graphs etc.

Data structure performs various operations to perform these data and also storing data to memory and retrieving data from memory.

Study of Data Structure

The study of data structure includes the following three steps.

Logical or mathematical description of the structure (Algorithm)

Implementation of the structure on a computer(Operation)

Quantitative analysis of the structure which includes determining the amount of memory needed to store the structure and the time required to process the structure (Time- space-complexity)

Classification of data structures

The data structure has variables associated with one another depending on the data. Data structure performed some basic operations.

• Organizing data
• Accessing data (Retrieving data
• Manipulating data for information (processing data)

The classification of data depends on above the operations these are as follows.

• Primitive data structures
• Non-Primitive data structures

Classification of Data Structure

Primitive data structures

These structures which are directly operated by machine level instructions and easily available in a programming language. The memory representation for these type of structure are predefined and the user can not change this. The storage structure of these data structures vary from one machine to another. Examples of primitive data structures are integer, float, character, double and pointer.

Non-Primitive Data Structures

These structures are rarely available in a programming language. They can not be operated by machine-level instructions. The storage representation or memory representation is not predefined. User has to define them i.e. user-defined structures. Examples of non- primitive data structures are arrays, stacks, queues, files and linked list.

Non-primitive data structures are further classified into two types.

•     Linear data structures and
•     Non-Linear data structure

Linear Data Structures

A data structure is said to be linear if its elements form a sequence, or a linear list (the group of adjacent data). This property is called as adjacency between the elements. Examples of linear data structures are arrays, stacks, linked lists and queues.

Array: An array is a finite set of homogeneous elements stored in adjacent memory locations. It is represented by a single name with its index. The first element is num[0], the second element is num[1] and so on. The last element is num[N-1], Here in fig. num[4].

Structure of Array

Linked list: A linked list is a linear collection of data items called nodes. Each node is divided into two parts Information field and Link field.  Each node has an information field and a pointer, pointing to the next node of the list called the linked field. It starts with a HEAD pointer, which stores the pointer value of first node. The first node points to the second node and so on. The last node does not point to anything, so it is indicated as a NULL pointer.

Link list

Stack: Stack is a linear data structure in which data is inserted called push and deleted means pop at one end called top of the stack. Here data are stored in the Last-In-First-Out manner.

Stack of  data structure

Queue: Queue is a linear the data structure in which data items can be inserted from one end called the REAR and the data items can be deleted from the other end called the FRONT.

Queue in Data Structure

Non-Linear Data Structures

The data structures in which data items are not arranged in order are called Non-linear data structures. They may exhibit either a hierarchical relationship or a parent-child relationship. Example- Trees and Graphs.

Trees: A Tree is a recursive data structure containing the set of one or more data nodes where one node is designated as the root of the tree while the remaining nodes are called as the children of the root. They are maintaining either a parent-child relationship between them or they are sister nodes. In general, the tree has any number of children nodes but it can have only a single parent.

Tree in Data Structure

Graphs: A graph is a pictorial representation of a set of objects where some pairs of objects are connected by links. The interconnected objects are represented by points termed as vertices, and the links that connect the vertices are called edges. 

The graph in Data Structure