Basic Concept of Database

Data: Data is sequence of digit. It is raw materials of information.

System: Some related things make a system. System is divided three steps.

(1)               Input

(2)               Processing

(3)               Output

Data Dictionary: Data Dictionary is a file which content the primary description of information of data file data under database.

Data Structure: The process of arranging databy many way is called data structure.

The flowing are data structure

(1)               Array

(2)               Record

(3)               Stack

(4)               Queue

(5)               Tree

(6)               Linked List

Array: Array means class Arranging same kinds of data is called Array. There are three kinds of array

1. One Dimensional Array
2. Two Dimensional Array
3. Three Dimensional Array

Record: The collection of some field is called record.

Stack: Stack is one kinds of data structure where LIFO (Last in First Out) process is flowed.

Queue: Queue mean line or row. In this structure Last kept data use first. This system is Called FIFO

Tree: In this structure data are input hierarchically.

Pointer: Pointer is an indicator in data structure pointer use to speed up the computer.

String: Combination of some ward is string such as Karim, Rahim, Masud, Dhaka etc.

String Variable: If Variable will be ward is Called String. Normally First character of field name is string which express by first character with $ Sign

Entity: Each record in he data file of database is called entity.

Attribute: Each field in record of data file of database is called Attribute.

4GL: Forth Generation Language. The Database management language is called Forth Generation Language.

• Characteristics of RDMS

1. We can find the information by different condition
2. We can create customize form to input data

Data Schema: The over all Design of database is called database Schema.

Database Schema: Data management system has special language which is called database language.

There are two kinds of database language.

1. Procedural language
2. Non – procedural language

DML: The language of DBMS by which data can be manipulated in the Database.

DDL: By this language describe data schema definitely by expressing a expressing a set of definition.

Procedural DML: In this language system the user define data will be store what kind of database and how can retrieve that data.

Non – Procedural Language: In this Language system the user only define data will be store what types of database but no need to define how data will be retrieve.

Topology

The logical and physical collection of computer in a network is called  topology .Topology means now a days physical topology .
Classifications are :
a.      Bus topology
b.      Ring  topology
c.       Star topology
d.      Tree topology
e.       Mesh topology
f.        Hybridge topology
Bus
In a bus topology all computers are connected to a central cable called bus or backbone.
Star
A star topology is intended with each node (file server, workstations, and peripherals) connected straightforwardly to a central network Devices. Data on a star network passes through the network Devices before continuing to its destination. The network Devices manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable. Though, it can also be used with coaxial cable or fiber optic cable
Ring
A ring topology may show to be the same as a star topology. on the inside, the MAU (multistation access unit) of a ring contains wiring that allows information to pass from one device to another in a circle or ring . The Token Ring protocol uses a ring topology.
 Tree                                                     
A tree topology is the combination of characteristics of linear bus and star topologies. It consists of groups of star-configured workstations linked to a linear bus backbone cable. Tree topologies permit for the extension of an existing network, and enable  to configure a network to meet their needs.