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Computer Science Basics for Class VIII & IX

1. Internet

The Internet is a worldwide telecommunications system that provides connectivity for millions of other,

smaller networks; therefore, the Internet is often referred to as a network of networks. It allows computer

users to communicate with each other across distance and computer platforms.

2. TCP/IP protocols

The two most important protocols allowing computers to transmit data on the Internet are Transmission

Control Protocol (TCP) and Internet Protocol (IP). ith these protocols, virtually all computers can

communicate with each other.

3. Domain name system D!S"

!n Internet address has four fields with num"ers that are separated "y periods or dots. This type of addre

is known as an IP address. #ather than have the user remem"er long strings of num"ers, the $omain %am

&ystem ($%&) was developed to translate the numerical addresses into words.

#. $%s

!ddresses for we" sites are called '#s ('niform #esource ocators). ost of them "egin with http

(*yperte+t Transfer Protocol), followed "y a colon and two slashes.

'. Broa()an(

road"and internet connections provide high-speed internet that is always on and allows for more data to

transmitted than the traditional dial-up connections. 'nlike dial-up services, it does not "lock phone line

and you do not have to reconnect to the network each time you log off.

*. +i,-i

i-i is a play on the term *i-i and represents a wireless internet connection. ore specifically, it is a

wireless local area network (!%) that allows devices to connect wirelessly to the internet. It utili/es 0

2*/ and 3.4 2*/ radio waves to connect i-i ena"led gadgets.

. +i0X

i!5 is a more advanced form of wireless internet technology than i-i. It aims to provide the high

speeds of "road"and connections, the large coverage of phone networks, and the convenience of i-i in

one package.

8. Networking

 %etworking is the practice of linking multiple computing devices together in order to share resources. Th

resources can "e printers, C$s, files, or even electronic communications such as e-mails and instant

messages.

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. Sitces

&witches are used in order to connect many devices on the same network. These devices are generally

within the same "uilding, such as an office "uilding or school and could consist of various computers,

 printers, and other gadgets.

14. %outers

In addition to switches, networks generally employ routers as well. These essential tools connect differennetworks to each other through the internet in order to allow for data e+change "etween networks.

11. Network Types

There are countless types of networks availa"le, especially as networking technologies continue to advan

Two of the most commonly employed networks are !% and !%.

6 ocal 0rea !etor5 0!"6 These networks are used to connect devices over relatively short distanc

such as within a "uilding, school, or home. !%s generally

7 +i(e 0rea !etor5 +0!"6 These networks are used to connect devices over much larger distances t

!%s. ! !% is esta"lished "y using routers to connect various

6 8ter !etor5 Types6 7arious other types of networks e+ist, including wireless local area networks

(!%s) that are !%s "ased on wireless network technology and metropolitan area networks (!%s)

that cover larger areas than !%s "ut smaller areas than !%s.

12. Network Topology

6 Bus6 This topology utili/es a common "ack"one, generally a single ca"le, to connect all the devices onnetwork.

6 %in96 ound in some offices and schools, ring topologies give each device two neigh"ors for

communication purposes. !ll data travels in a ring, and a failure of that ring can "ring down the whole

network.

6 Star6 ound in many homes, a central connection known as a 8hu"9 is connected to all the o":ects on th

network. This hu" could "e a router or a switch.

6 Tree6 ! hy"rid "usstar network, several star hu"s are connected to the core ca"le of a "us in order to

vastly increase the num"er of computers a"le to connect to the network.

6 es< The mesh topology employs the concept of routing, in which each piece of data sent on the netw

has multiple paths it can take instead of one fi+ed route. The internet is a perfect e+ample of this topology

13. 8peratin9 System

!n operating &ystem (=&) is an intermediary "etween users and computer hardware. It provides users an

environment in which a user can e+ecute programs conveniently and efficiently.

1#. -unctions of 8peratin9 System

ollowing are some of important functions of an operating &ystem.

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• emory anagement

• Processor anagement

• $evice anagement

• ile anagement

• &ecurity

• Control over system performance

• >o" accounting

• ?rror detecting aids

• Coordination "etween other software and users

1'. Types of 8peratin9 Systema) Batch operating system

b) Time-sharing operating systems

c) Distributed operating ystem

d) Network operating ystem

e)!eal Time operating ystem

1*. Basic Concepts of Data)ase

! data"ase is :ust what the name implies, a "ase collection of data. The data is organi/ed in some manner so that t

information contained within the data"ase can "e easily retrieved.

-iel( Column"6 a single piece of information. Could "e a name, or a num"er. In some cases, it may ev

 "e a null or empty value.

%ecor( %o"6 a collection of related fields. ! num"er of pieces of information that relate to the same o":ect. o

e+ample< If you keep records on an employee, you might have their name, address, social security num"er, phonenum"er, etc@?ach piece of the information relates "ack to one employee. This would "e the employeeAs record.

 Ta)le -ile"6 a collection of related records. If you put all the employee records together, you have a ta"le of

employees.

Data)ase6 a collection of ta"les. If you were keeping the company records, you might have a ta"le for employees

ta"le for customers, and another for sales records. !ll these ta"les would "e com"ined as a data"ase.

! %elational Data)ase ana9ement System DBS" B software that allows users to create, maintain, and uery

your data in the related ta"les.

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 &ome common $& programs are !ccess, icrosoft &D &erver, =racle, o+Pro, #ase, and Parado+

1. Primary an( -orei9n :eys

  hen we start thinking of constructing the various ta"les that our data"ase reuires, we need to conside

how we will organi/e these ta"les and relate them to one another. or the most part, this will "e done us

keys. There are 0 types of keys in a ta"le.

Primary Eey a value that is uniue to each record

oreign Eey a primary key of one ta"le included in another ta"le

1;. *T is a mar5up language for (escri)in9 we" documents (we" pages).

• *T stands for