Data Base

 A  Data Base is a collection logically related data sets or file. Normaly, these files /data sets are of different nature, used for specific purposes. these may be organized in various ways to meet processing and retrieval requirements of the organizations or users. 

                                    A  Data base system is just a computerized record keeping system. A data base itself can be regarded

as a kind of electronic file cabinet, a warehouse or a repository for a collection of computerized data files. the user of he database normally has he following facilities to enjoy.

• Adding new , blank file to the database.
• Inserting new data into the existing files.
• Retrieving data from existing files.
• Updating data in existing files.
• Deleting data from existing files.
• Removing existing files, empty or otherwise from the database.

A database system involves four major components, namely.

            Data                   The Information

            Hardware            The physical components i.e.,

                                            Secondary Storage

                                            I/O devices

                                            Device controllers

                                            I/O channels

                                            Processors

                                            Main memory

            Software             User/system software

                                            Set of programs

                                            Utilites

           Personnels           The people

                                            Programmers/Analysts

                                            End users

                                            Database Administrators      

      Database Objectives

  There are at least three main objectives for for using the data base organization.

• Data Integration: In a database, information is coordinated from different files and operated on a single file.Logically, the information is centralized, physical data may be located on different devices i.e., scattered around over on different locations, connected through data communication links.
• Data Integrity: If a data item is contained in more than one file, then all files must be updated if that item is changed.In a database, only one copy of data is kept, therefore, the data is more consistent.
• Data Interdependence: If the format of file is changed, than all the programs have to be changed. However, a database allows the organization of data to be changed without the need to re-program. It allows programs to be modified without re-organization of data.

Types of Database Models. 

There are three types of Logical Database Models.

• HIERARCHICAL Model: This Model has the general shape or appearance of an Organizational Charts. A node on the chart, representing a particular Entity is subordinate at the next highest level, just as on an organizational char, an employee reports to only boss. This kind of structure is often referred to as an "Inverted Tree", with the top most referred to as the "Root"

• NETWORK Model: This is somewhat similar to that of the Hierarchical model but has one major difference.subordinate entities, depicted by arrows on the network diagram, may participate in as many subordinate relationships as desired. Therefore a much more complex diagrams may be used to represent the structure of the database. Networks provide more flexibility than a simple hierarchical system in the data relationships may be maintained.

• RELATIONAL Model: This system consists of a collection of simple files/Relations (Entities), each of which has no structural or physical connection such as those typical used in hierarchical or network system.                                                                                                           The various entities possess the interrelationships as depicted by a network like diagram. But these relationships are based on the data content of the entities involved, not by pointer chains or other types of structural connection techniques.

Database Management System 

The data base management system (a collection of programs) which is used for storing and manipulating database is called database management system (DBMS). It is an improvement over the traditional file management system (DBMS). It is an improvement over the traditional file management systems. It uses DBMS software (database manager) Which control the overall structure of a database and access to the data itself.