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COMPUTER SECURITY

LESSON 16

COMPUTER SECURITY

DEFINITION OF COMPUTER SECURITY

Computer security means protecting ourcomputer systems and the information theycontain against unwanted access, damage,destruction or modification.

We need to protect our computer from any

intruders such as hackers, crackers and scriptkiddie.

We do not want strangers to read our e-mail, use our computer to

attack other systems, send forged e-mail from our computer, or examinepersonal information stored on our computer such as financial statements.

TYPES OF COMPUTER SECURITY

Three types of computer security are:

a) hardware security

b) software securitydata security

c) network security

a) HARDWARE SECURITY

!ardware security refers to security measures usedto protect the hardware specifically the computerand its related documents.

The examples of security measures used to protect

the hardware include "C-locks, keyboard-locks,

smart cards and biometric de#ices.

b) SOFTWARE AND DATA SECURITY

$oftware and data security refers to the security

measures used to protect the software and the lossof data files.

%xamples of security measures used to protect the

software are acti#ation code and serial number.

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&n example of security measure used to protect the loss of data files is the

disaster reco#ery plan method. The idea of this plan is to store data,program and other important documents in a safe place that will not beaffected by any ma'or destruction.

c) NETWORK SECURITY

The transfer of data through network has become a

common practice and the need to implementnetwork security has become significant.

(etwork security refers to security measures used

to protect the network system. ne example of

network security measures is firewall. With firewall, network resources canbe protected from the outsiders.

PERSONAL COMPUTER SECURITY CHECKLIST

*n order to make sure our computers are secured, here are the computer

security checklist to follow.

+o not eat, drink or smoke near the computer

+o not place the computer near open windows or doors +o not sub'ect the computer to extreme temperatures

Clean the euipment regularly "lace a cable lock on the computer

se a surge protector $tore disks properly in a locked container

aintain backup copies of all files

$tores copies of critical files off sites $can a floppy disk before you open it +o not open any unknown email recei#ed

LESSON 17

INTRODUCTION COMPUTER THREATS

The computer is a great tool to store important information. *n certain

cases, the information is #ery #ital that losing it will harm the computer

system.

Computer threats can come from many ways either from human or natural

disasters. /or example, when someone is stealing your account informationfrom a trusted bank, this threat is considered as a human threat. !owe#er,

when your computer is soaked in hea#y rain, then that is a natural disasterthreat.

MALICIOUS CODE

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alicious code is also known as a rogue program. *t is

a threat to computing assets by causing undesiredeffects in the programmer0s part. The effect is causedby an agent, with the intention to cause damage.

The agent for malicious code is the writer of the code,

or any person who causes its distribution. There are

#arious kinds of malicious code. They include #irus, Tro'an horse, logic door,trapdoor and backdoor, worm and many others.

a) VIRUS

a program that can pass on the malicious

code to other programs by modifying them

attaches itself to the program, usually files

with .doc, .xls and .exe extensions

destroys or co-exists with the program

can o#ertake the entire computing system and spread to other

systems

b) TROJAN HORSE

a program which can perform useful and

unexpected action

must be installed by users or intruders

before it can affect the system0s assets

an example of a Tro'an horse is the login script that reuests for

users0 login *+ and password

the information is then used for malicious purposes

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c) LOGIC BOMB

logic bomb is a malicious code that goes off when a specific

condition occurs.

an example of a logic bomb is the time bomb

it goes off and causes threats at a specified time or date

) TRAPDOOR OR BACKDOOR

a feature in a program that allows

someone to access the program withspecial pri#ileges

!) WORM

a program that copies and spreads itselfthrough a network

P"#$a"% D#!!"&c' B(& W*"$' A&+ ,#"-''

W*"$

perates through the network

$preads copies of itself as astandalone program

V#"-'

$preads through any medium

$preads copies of itself as aprogram that attaches to otherprograms

HACKER

!acking is a source of threat to security in computer.

*t is defined as unauthorised access to the computer

system by a hacker.

!ackers are persons who learn about the computer system in detail. They

write program referred to as hacks. !ackers may use a modem or cable to

hack the targeted computers.

NATURAL AND ENVIRONMENTAL THREATS

Computers are also threatened by natural or en#ironmental disaster. 1e it athome, stores, offices and also automobiles.%xamples of natural anden#ironmental disasters:

/lood

/ire

%arthuakes, storms and tornados

%xcessi#e !eat

*nadeuate "ower $upply

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THEFT

Two types of computer theft:

2) Computer is used to steal money, goods,

information and resources.3) $tealing of computer, especially notebook and

"+&s.

Three approaches to pre#ent theft:

2) pre#ent access by using locks, smart-card or

password3) pre#ent portability by restricting the hardware

from being mo#ed4) detect and guard all exits and record any

hardware transported

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SECURITY MEASURES

Today, people rely on computers to create, store and manage critical

information. *t is important that the computer and the data they store areaccessible and a#ailable when needed. *t is also important that users takemeasures to protect their computers and data from lost, damage andmisused.

$ecurity measures mean the precautionary measures taken toward possible

danger or damage. There are 5 type of security measures.

1) DATA BACKUP

+ata 1ackup is a program of file duplication. 1ackupsof data applications are necessary so that they can

be reco#ered in case of an emergency.

+epending on the importance of the information,

daily, weekly or biweekly backups from a hard diskcan be performed.

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.) CRYPTOGRAPHY

Cryptography is a process of hiding information by altering the actual

information into different representation, for example, an &"& can bewritten as *6 7.

&lmost all cryptosystems depend on a key such as a

password like the numbers or a phrase that can be used to encrypt or

decrypt a message.

The traditional type of cryptosystem used on a computer network is called a

symmetric secret key system.

/) ANTIVIRUS

&n anti#irus program protects a computer against#iruses by identifying and remo#ing any computer#iruses found in the computer memory, onstorage media or incoming e-mail files.

&n anti#irus program scans for programs that

attempt to modify the boot program, the operatingsystem and other programs that normally are read from but not modified.

IDENTIFYING VIRUS

Two techniue are used to identify the #ir

VIRUS SIGNATURE

&lso called a #irus definition is a

specific pattern of the #irus code.

INOCULATING A PROGRAM FILE

The anti#irus program recordsinformation such as the file si8e and filecreation date in a separate inoculationfile.

The anti#irus program then uses this

information to detect if a #irus tampers

with the data describing the inoculatedprogram file.

*f an anti#irus program identifies an infected file, it attempts to remo#e its

#irus, worm or Tro'an horse. *f the anti#irus program cannot remo#e theinfection, it often uarantines the infected file. 9uarantine is a separate

area of a hard disk that holds the infected file until the infection can beremo#ed. This step ensures other files will not become infected. "atents forin#entions tility, design or plant patents that protect in#entions andimpro#ements to existing in#entions

0) ANTISPYWARE

$pyware is a program placed on a computer withoutthe user0s knowledge. *t secretly collects information

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The spyware program communicates information to

the outside source.

&n anti-spyware application program sometime called tracking software or a

spybot is used to remo#e spyware.

&mong of the popular anti-spyware programs are:

$pybot $earch and +estroy

&d-aware

$pyware 1laster

2) FIREWALL

/irewall is a piece of hardware or software whichfunctions in a networked en#ironment to pre#ent somecommunications forbidden by the security

policy.

/irewall implement a security policy. *t might permit

limited access from in or outside the networkperimeters or from certain user or for certain acti#ities.

6) HUMAN ASPECTS OF SECURITY MEASURES

!uman aspects refer to the user and also the intruderof a computer system.

*t is one of the hardest aspects to gi#e protection to.

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The most common problem is the lack of achie#ing a good information

security procedure.

LESSON 13

RELATIONSHIP BETWEEN SECURITY THREATS AND

SECURITY MEASURES

$ecurity threats may come from in many forms. /or example, when

someone is in#ading your account information from a trusted bank, this actis considered as a security threat.

$ecurity measures can be used to pre#ent this in#ader

from getting the account information. /or example, thebank can use a firewall to pre#ent unauthorised access toits database.

SECURITY THREADS

$ecurity threats may come from in many forms. /or example, when

someone is in#ading your account information from a trusted bank, this actis considered as a security threat.

$ecurity measures can be used to pre#ent this in#ader from getting the

account information. /or example, the bank can use a firewall to pre#entunauthorised access to its database.

MALICIOUS CODE THREATS VS4 ANTIVIRUS AND

ANTISPYWARE

$ecurity threats include #irus, Tro'an horse, logic bomb, trapdoor andbackdoor, and worm.

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&nti#irus and anti-spyware can be used to protect the computer from the

threats by:

limiting connecti#ity

allowing only authorised media for loading data and software

enforcing mandatory access controls

blocking the #irus from the computer program

HACKING VS4 FIREWALL

!acking is an unauthorised access to the computer

system done by a hacker. We can use firewall orcryptography to pre#ent the hacker from accessing

our computers.

& firewall permits limited access to unauthorised

users or any acti#ities from the network en#ironment. Cryptography is aprocess of hiding information by changing the actual information into

different representation, for example, an &"& can be written as ;

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BE SUPSPICIOUS OF ALL RESULTS

There are many instances where non-programmers

de#elop applications which are not built with properunderstanding of software engineering practices.

+ata produced by such applications may not be

correct and may risk corrupting data recei#ed from

other sources that are not compatible with theapplication.

LESSON .5

SECURITY PROCEDURES

Computers should ha#e alarm systems to guard them from any attacks such

as #iruses and data corruption. The alarm system is the security measuresthat we take to ensure its safety.

DATA PROTECTION

We need to protect the data in the computer as itmay somehow get lost or corrupted due to some#iruses or mishap like fire, flood, lightning, machinefailures and e#en human errors.

There are a few ways to protect the information namely:

make backup files detect the #irus and clean the computer warn others on #irus attacks

1) BACKUP FILES

sers can do backups of file systems by: keeping the duplicated files in external storage

such as in the floppy disk and thumb dri#e do backup freuently

.) DETECT VIRUS AND DO CLEANUP

& computer #irus is able to affect and infect the waythe computer works. >iruses can be detected when

we run an anti#irus program.We can also delete theinfected files and documents.

/) WARN OTHERS ON VIRUS

ATTACK

We can warn others on #irus attacks or new #iruses

by sending e-mails to them.

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DETECTING ILLEGAL ACCESS TO SYSTEMS

The computer system is able to detect any illegal access to the system by auser who does not ha#e any authorisation. 1asically, a corporation willsimply use tcpwrappers and tripwire to detect any illegal access to theirsystem. ser?s access will be re#iewed periodically by computer operations.n going internal audits will be made to ensure detection of #iolations ofsecurity and unauthorised modifications to software and data .

TCPWRAPPERS

Tcpwrappers stop the attempted connection

examines its configuration files

will decide whether to accept or re'ect the reuest.

Tcpwrappers will control access at the application le#el, rather than at the

socket le#el like iptables and ipchains. The system will run tcpwrappers tolog access to ftp, tftp, rch, rlogin, rexec and telnet.

TRIPWIRE

Tripwire will detect and report on any changes in the

thousands of strategic system files.

The system will run tripwire to determine if system

files ha#e changed.

PREVENTING ILLEGAL ACCESS TO SYSTEMS

!a#e any of you e#er been to an airport6 +o you know the do0s and don0ts

when you are at the airport6

There are things that cannot be taken inside the airplane. *t is for the

purpose of security procedures.

*t is the same as computer systems. *t would not allow any unauthorised

users to simply access the system.

Ways to pre#ent illegal access to systems:

2. @un anlpassword to make password cracking difficult.

3. @un tcpwrappers to check if the name for an ip address can be

pro#ided by +(C4. se a callback system to pre#ent unauthorised use of stolen

passwords.

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PREVENTING ILLEGAL ROOT ACCESS

To pre#ent any illegal root access, we should ha#e

S-+*so that people can perform on some machinewithout getting access to the entire root if that is notreuired. *n addition, with $udo we did not ha#e togi#e out the root password.

S-+*stands for A$uperuser do) and is a program in nix, Binux and similar

operating systems such as ac $ 7 that allows users to run programs in

the form of another user Anormally in the form of the system?s superuser).

S-+*allows a permitted user to execute a command as the superuser or

another user, as specified in the sudoers file.

PATCH

"atch supplies small updates to software, pro#ided

that the source code is a#ailable.

"atch is a name of an (*7 utility. *t applies a script

generated by the different program to a set of filesthat allows changes from one file to be directlyapplied to another file.

@esources are not enough to patch all security holes that we hear about

through the bugtraqlist.

(Bugtraq is a full disclosure mailing list dedicated to the issues of computersecurity. On-topic discussions are new discussions about vulnerabilities,

methods of exploitation and how to fix them. It is a high volume

mailing list and almost all new vulnerabilities are discussed there.

LESSON .1

COMPUTER APPLICATIONS IN THE SOCIETY

The computer has change the society today as much as industrial re#olution

changed society in 2thand 2Dthcentury. "eople interacts directly with

computer in education, finance, go#ernment, health care, science,publishing, tourism, and industry.

Computers help them to do their work faster and more efficient by using the

software application that consist of special program for specific task.

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SOFTWARE APPLICATIONS

$oftware applications are used for many reasons. $uch as to enhance thelearning process, to help in business acti#ities, to assist the graphics andmultimedia pro'ect and to fasilitate communication.

A"a

!ome and%ducation

1usiness

Eraphics

and ultimedia

Ea$89' *! '*!(a" a889#ca(#*&'

*ntegrated software, "ersonal finance, Begal, Tax"reparation,Clip &rt*mage Eallery, !ome +esignBandscaping and

@eference

Word "rocessing, $preadsheet, +atabase, "resentation

Eraphics, "ersonal *nformation anager, $oftware $uite,

"ro'ect anagement and &ccountingComputer-aided design AC&+), +esktop "ublishing,

"aint*mage %diting, >ideo and &udio %diting, ultimedia&uthoring and Web "age &uthoring

Communication %-mail, Web 1rowsers, Chat @ooms, (ewsgroups, *nstant

essaging, Eroupware and >ideo Conferencing

These software application comes in packages.

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SOFTWARE APPLICATIONSPACKAGES

S*!(a" A889#ca(#*&

Word "rocessing

$preadsheet

+atabase

"resentation Eraphics

"ersonal *nformation

anager

$oftware $uite

"ro'ect anagement

&ccounting

Ea$89' *! P*8-9a" Pac:a;'

icrosoft Word and Botus Word "ro

icrosoft %xcel and Botus 2-3-4

icrosoft &ccess and icrosoft >isual /ox"ro

icrosoft "ower "oint and Botus /reelanceEraphics

icrosoft utlook and "alm +esktop

icrosoft ffice and Botus $mart$uite

icrosoft "ro'ect and Corel C&T&BF$T

F1 and "eachtree Complete &ccounting

HOME AND EDUCATION

Today, computers are used in schools, colleges anduni#ersities in order to promote better education byusing computers. *n the labs, students use softwarepackages to complete their assignments. &t thesame time, some educators use the computer-basedtraining and web-based training as replacements forlecture presentation.

$ome of the software applications that are usually used in schools and

uni#ersities include icrosoft ffice, &dobe "hotoshop, acromedia /lash,&utoC&+, acromedia +reamwea#er and acromedia +irector.

COMPUTERS FOR HIGHER EDUCATION

pen +istance Bearning A+B) or online learning can

be implemented as computers are the main medium in

deli#ering the knowledge from one location to theother locations.

This type of learning consists of online forum,

discussion, ui88es, test uestions and many more.The example of the pen +istance Bearning institution is the pen ni#ersityof alaysia Awww.oum.edu.my).

BUSINESS

"eople use finance or accounting software to balance check books, pay bills,

track personal income and expenses, manage in#estments and e#aluatetheir financial plans.

&ccounting software helps companies to record and report their financial

transactions. %xamples of these software applications include F1, *ntuit9uick 1ooks and "eachtree Complete &ccounting.

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COMPUTERS IN BANKING

*n the banking sector, many financial institutions offer online banking.

"eople can access their financial records from anywhere in the world. neexample of online banking is aybank3u. Awww.maybank3u.com)

ost of the packages on banking offer a #ariety of online ser#ices. Which

reuires access to the web./or example we can track our in#estment online, compare insurance ratesand do online banking.

INDUSTRY

1y using the C& system, computers record actual

labour, material, machine and computer time used tomanufacture a particular product.

Computers process this data and automatically update

in#entory, production, payroll and accounting recordson the company0s network.

%xamples of companies using this system are "rotonAwww.proton.com.my)

and "erodua Awww.perodua.com.my).

GRAPHICS AND MULTIMEDIA

Computers are crucial in publishing especially in theprocess of making works a#ailable to the public.These works include maga8ines, books, newspapers,

music and film production.

$pecial software applications are used to assist graphic designers to de#elop

graphics, texts, photographs and composing songs.

Computer-&ided +esign, +esktop "ublishing, "aint*mage %diting, >ideo and

&udio %diting and ultimedia &uthoring are among the popular applications

software.

COMMUNICATION

& go#ernment pro#ides society with direction bymaking and administering policies. ost go#ernment

offices or agencies ha#e websites in order to pro#ideciti8ens with up-to-date or latest information.

%xamples of software applications used for

communication include e-mail, web browsers,newsgroups, instant messaging and #ideo conferencing.

"eople can access go#ernment websites to:

check information on taxesAwww.hasil.org.my)

apply for permits and licenses Awww.'p'.go#.my)

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http://www.maybank2u.com/http://www.maybank2u.com/http://www.hasil.org.my/http://www.hasil.org.my/http://www.jpj.gov.my/http://www.jpj.gov.my/http://www.maybank2u.com/http://www.maybank2u.com/http://www.hasil.org.my/http://www.hasil.org.my/http://www.jpj.gov.my/http://www.jpj.gov.my/

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check for yGadAwww.'pn.go#.my)

pay parking tickets and check summons Awww.'p'.go#.my)

renew #ehicle registration Awww.'p'.go#.my)

register online for *"T&*"T$ application Awww.moe.go#.my)

COMPUTERS IN TOURISM

Today, people will go online to get all related

information about tra#eling. They can #isit websites toget information on destinations, prices, hotels, flights

and car rentals.

They can also purchase ticket online, all payments can

be made by using credit card.

COMPUTERS IN THE HEALTHCARE

*n the medical field, computers are #ery important in

running the operations. edical staffs use computersfor #arious purposes, namely:

maintaining patient records

monitoring patients0 #ital sign

assisting doctors, nurses and technicians with medical tests by usingcomputer and computerised de#ices .

using medical software to help with researching and diagnosing healthconditions.

/urthermore, computers and the internet are important sources for people to

get all information on medical, nutrition, fitness and other tips from se#eral

a#ailable websites. The latest de#elopment in the medical field istelemedicine. This technology is meant to help professional to conduct li#e

conference in separate locations around the globe.

SCIENCE

*n the scientific world, computers are used in allfields of science from biology to astronomy tometeorology and others. These are things thatcan be done by computers, namely:

collecting, analy8ing and modelling data

ser#ing as medium of communication with colleagues around the world

contributing to new in#entions or breakthrough in surgery, medicine

and treatment imitating functions of the central ner#ous system, retina of the eye

and others by tiny computers allowing a deaf person to listen through cochlear implant

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http://www.jpn.gov.my/http://www.jpn.gov.my/http://www.jpn.gov.my/http://www.jpj.gov.my/http://www.jpj.gov.my/http://www.jpj.gov.my/http://www.jpn.gov.my/http://www.jpn.gov.my/http://www.jpn.gov.my/http://www.jpj.gov.my/http://www.jpj.gov.my/

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LESSON ..

COMPUTER USERS

"eople around the world rely on computers to do so many things. They arefrom different backgrounds and are di#ided in H categories.

HOME USERThe computer is a basic necessity. %ach home user

spends time on the computer for different reasons: business

communication entertainment

education

SMALL OFFICE

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obile users:

include real estate agents, insurance agents, meter readers and

'ournalists

use notebook computers, *nternet-enabled "+&s or smart phones

work with basic business software such as word processing andspreadsheet business software

use presentation graphics software to create and deli#er presentationsto a large

audience by connecting a mobile computer or de#ice to a #ideo

pro'ector

POWER USER

"ower users reuire the capabilities of workstationcomputers or other types powerful computers. Thesoftware that is used by power users is normally

expensi#e because of their speciali8e design. Theircomputer ha#e network access connections andinternet connections.

"ower users:

include engineers, scientists, architects and #irtual reality animators

use computers with extremely fast processor, bigger storage andcustomised software

work with mini computers that uses design to meet the organisationalneeds

use software such as C&+, C& and &TB&1%xamples :

LARGE BUSINESS USER

%ach employee or customer who uses computer inlarge offices of company is a large business user.Barge business users use a large network ofcomputers. se computers for basic business acti#itiessuch as preparing bills for millions of customers,preparing payroll and managing thousands of items in

the in#entory.

Barge business users:

bank, insurance company, hypermarket use computers for basic business acti#ities

ha#e e-commerce that allow customers and #endors to interact and dobusiness transactions online therefore customers, #endors and otherinterested parties can access information on the web

ha#e e-mail and web browsers to enable communications amongemployees, #endors and customers

pro#ide kiosks in public locations

any employees of large business telecommute, which means they workaway from their offices workstation. They also ha#e flexible schedule.

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SYSTEM CONCEPT

LESSON .7

OVERVIEW OF COMPUTER SYSTEM

These de#ices are examples of computer hardware. & computer system

needs to ha#e these hardware to function.

COMPUTER SYSTEM

& computer system is defined as combination of components designed toprocess data and store files.

& computer system consists of four ma'or hardware componentsI input

de#ices, output de#ices, processor and storage de#ices.

& computer system reuires hardware, software and a user to fully function.

$oftware refers to set of instructions that tell the hardware what to do.

$oftware can also ha#e #arious other functions such as performingcomputation, communication with other software and human interaction.

ser refers to a person who uses the computer for any purposes such as

work, business and entertainment.

COMPUTER HARDWARE

Computer hardware consists of:

input de#ices

processor

output de#ices

storage de#ices

I&8-( D,#c'

*nput de#ices feed data or commands in a form that the computer can use.%xample of input de#ices are:

Geyboard

Bight "en

Joystick

icrophone

ouse

>ideo

+igital camera.

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P"*c''*"

The C" is an example of a processor. *t has the

same important as the brain to human being.

O-(8-( D,#c'

utput de#ices such as the monitor shows

people the process data or information. Thistype of information can be understood and use

by computer user. ther example of outputde#ices are:

"rinter "lotter

$peaker

S(*"a; D,#c'

$torage usually means secondary storage. *t

consists secondary storage de#ices such ashardisk, /loppy +isk, diskette, C+ @ and +>+@.

COMPUTER SOFTWARE

There a 3 types of computer software, system software and applicationsoftware. $ystem software is any computer software that helps to runcomputer system. $ystem software controls, integrate and manages the

indi#idual component of a computer system.

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LESSON .>

INTRODUCTION TO COMPUTER SYSTEM

COMPUTER HARDWARE BLOCK DIAGRAM

&n *nput de#ice feed raw data to the processor. & processor processes raw

data and turns it into useful information. & storage de#ice keeps or storesboth process and unprocess data for later usage. &n output de#ice shows or

display the processed data.

INPUT DEVICES

When data is entered into the computer system, it is called an input. *nput

comes in #arious formsI texts, graphics, audio and #ideo. *nput de#ices are

needed to input data into the computer system.

Geyboard, mouse, scanner, barcode reader and digital camera are someexample of input de#ices.

OUTPUT DEVICES

utput is the result of raw input data that has beenprocessed by the central processing unit into

meaningful information. Common forms of outputare texts, numbers, graphics, sounds, animations

and #ideos.The most common output de#ices arecomputer screens, speakers and printers.

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STORAGE DEVICES

The system0s primary storage, @andom &ccess emory A@&) can only hold

data temporarily. Thus, secondary storage is needed to pro#ide additional

storage. The data stored in the secondary storage is considered permanentuntil it is deleted or remo#ed.

$econdary storage can be magnetic disks and optical disks. %xamples of

secondary storage are hard disks, rewritable C+s and +>+s as well as

remo#able disks such as pen dri#es.

PERIPHERAL DEVICES

%xternal hardware de#ices attached to the

computer are called peripheral euipments.

LESSON .3

INFORMATION PROCESSING CYCLE

+o you know how a computer works6 We use the computer in our e#eryday

li#es but not all of us know how this machine operates.

!uman uses the brain to think, make decisions and process information. &

computer has a brain too, and the brain of a computer is the processor or

the central processing unit AC") that processes information.

THE CENTRAL PROCESSING UNIT

The central processing unit or the C" is the brain of the computer.

&ll processing acti#ities are done in the C". *t

utilises the computer memory to execute instructionsfrom the application software and accomplish a task./or example: editing a letter, drawing a picture andsorting numbers.

The processor must be connected to input de#ices, output de#ices and

storage de#ices to carry out the abo#e mentioned tasks.

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THE INFORMATION PROCESSING CYCLE

ser will input the data to be processed by the processor.

The storage holds databases, files and programs. The output de#icespresent the processed data as useful information products for the user.

INPUT

*nput is any data or instructions that we enter into the computer system for

processing.

There are some common ways of feeding input data

into the system, which are:

typing on a keyboard

pointing with a mouse

C" accepts instruction from the user and translates the instruction into

readable information Adecode).

PROCESS

The processing unit controls all acti#ities within the system. /or e#eryinstruction, the control unit repeats a set of four basic operations called the

machine cycle:

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F(c?#&;

the process of obtaining a program instructions or data item from memory.

Dc*+#&;

the process of translating a program instruction into signals that thecomputer can execute.

Ec-(#&;

the process of implementing the instructions in a program.

S(*"#&;

the process of writing the result to the storage or memory.

STORAGE

$torage is a location which data, instruction andinformation are held for future use. %#ery computeruses storage to hold system software and applicationsoftware.

When we issue a command to start the applicationsoftware, the operating system locates the program in

storage and loads it into memory.

& storage medium, also called secondary storage is the physical material in

the computer that keeps data, instruction and information.

& storage de#ice is the computer hardware that records or retrie#es items to

and from storage media.

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OUTPUT

utput is data that has been processed into a useful

form, called information. There are four types ofoutput, which are texts, graphics, audio and #ideo.

The text consists of characters that are used to

create texts, sentences and paragraphs.

Eraphics are digital representations of non text information such as

drawings, charts and photographs.

&udio is music, speech or any other sound. >ideo consists of images that

pro#ide the appearance of full motion.

LESSON /5

DATA REPRESENTATION

BINARY DIGIT

Computers recogni8e only two discretestates: on and off. These states can berepresented by two digits, K and 2. %ach Kor 2 is called a bit in the binary system.

1it is the smallest unit of data a computercan process. 1it is a short for binary digit.

The binary system has a base of 3 withthe two digits AK and 2). Combinations of

Ks and 2s represent larger numbers.

BIT

& bit is the smallest unit of data that the

computer can process. 1it is a short for binarydigit. & bit is represented by the numbers 2

and K. These numbers represent the binarysystem. They correspond to the states of on

and off, true and false, or yes and no.

&ll digital data use the binary system to process the information. This

information include letters, digits or special character.

BYTE

1yte is a unit of information built from bits. ne byte is euals to bits.

%ight bits that are grouped together as a unit. & byte pro#ides enoughdifferent combinations of Ks and 2s to represent 3H5 indi#idual characters.

ne byte represents a single character such as the number 4, letter b

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or a L symbol. 1its and bytes are the basis for representing all meaningful

information and programs on computers.

CHARACTER

> b#(' @ 1 b%(

ne byte represents one character such as &, ;, D and M.%ight bits that aregrouped together as a unit. & byte pro#ides enough different combinationsof Ks and 2s to represent 3H5 indi#idual characters.

/or example, the capital letter / is represented by the binary code K2KKK22K

that can be understood by the computer system. %ight bits grouped togetheras a unit are called a byte. & byte represents a single character in thecomputer.

CHARACTER CODES

There are three character codes to representcharacters which are &$C**, %1C+*C and nicode.%ach byte contains eight bits. & byte pro#ides enoughdifferent combination of Ks and 2s to represent 3H5characters.

The combinations of Ks and 2s are defined by patterns. These patterns are

called coding scheme. The 3H5-character capability of &$C** and %1C+*C istoo small to handle the characters that are used by other languages such as&rabic, Japanese and Chinese.

The nicode coding scheme is designed to sol#e this problem. *t uses two

bytes A25 bits) to represent one character. nicode will ha#e more than5H,KKK different characters. This can co#er all the world0s languages.

LESSON /1

INTRODUCTION TO BINARY CODING

COMMUNICATION CODES

$moke signals, orse code and semaphore are some of the communicationcodes used by people in the early days. *n the information digital era, peoplesend information #ia electronic de#ices such as through the computers.

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Computers use binary codes to communicate. ne of the widely used binary

codes is the A$"#ca& S(a&+a"+ C*+ !*" I&!*"$a(#*& I&("c?a&;=ASCII)4

HISTORY OF CHARACTER CODES

1efore people used binary codes such as &$C** to communicate #ia

computers, character codes were widely used as a medium ofcommunication. Bet0s look at some of the character codes used prior to the

use of &$C**.

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WHAT IS ASCII

&$C** pronounced as Nask-keyN stands for the &merican $tandard Code for

*nformation *nterchange and was proposed by &$& A&merican $tandard&ssociation) in D54 and was finalised in 2D5.&$C** is a standard of ;-bitcode used to represent characters, which include letters, numbers andpunctuation marks.

; bits allow the computer to encode a total of 23 characters for the

numbers K-D, uppercase and lowercase letters &-O and a few punctuationsymbols. !owe#er this 23 bit code only suitable for english languagespeaking users.

*1 and &pple expanded the amount of space reser#ed for the character

codes to -bits, eui#alent to 2 byte.

FUNCTIONS OF ASCII

&$C** was established to achie#e compatibility

between #arious types of data processingeuipment making it possible for the

components to communicate with each othersuccessfully.

&$C** enables manufacturers to produce components that are assured to

operate correctly in a computer.

&$C** makes it possible for humans to interact with a computer. *t also

enables users to purchase components that are compatible with theircomputer configurations.

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HOW ASCII WORKS IN A COMPUTER SYSTEM

When you press a key, for example the letter + on

your keyboard, the electronic signal is sent to the C"for the computer to process and store in memory.

%#ery character is con#erted to its correspondingbinary form. The computer the processes the letter asa byte., which actually a series of on and off of

electrical states. When the computer is finishedprocessing the byte, the software installed in the system con#ert the byteback which is then displayed in the screen. *n this example, the letter + iscon#erted to K2KKK2KK.

LESSON /.

DATA MEASUREMENT

Why is 2K3P bytes Q 2G16

KILOBYTE =KB) 3KQ 2*n mathematics, 2 G1 Q 2KKK bytes. 32Q 3

*n computer, 2 G1 Q 2K3P bytes or 33Q P

can be said as: 34Q

3PQ 25

1 KB @ .15b%(' 3HQ 43

35Q 5P

This is how we get the calculation for 2K3P

bytes.

MEGABYTE =MB)

2 1 Q 2 KP H;5 bytes or it can be said as:

1 MB @ ..5b%('

GIGABYTE =GB)

2 E1 Q 2 K;4 ;P2 3P bytes or it can be said as:

1 GB @ ./5b%('

TERABYTE =TB)

2 T1 Q 2 KDD H22 53; ;;5 bytes or it can be said as:

1 TB @ .05b%('

79

3;Q 23

3Q 3H5

3DQ H2332KQ 2K3P

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LESSON //

CLOCK SPEED MEASUREMENT

EVOLUTION OF COMMUNICATION

When people talk about a computer0s RspeedS, theymean how fast it can process data. *n other words,this means the speed the computer can turn data intoinformation.

%#ery microprocessor contains a system clock. The system clock controls the

speed of all the operations within a computer. The speed of the clock ismeasured by how many cycles per second the clock makes.

HERT AND SECONDS

The clock speed unit is measured in hert8. & hert8 is one cycle per second.

MEGAHERT =MH)

ega is a prefix that stands for million. Thus, megahert8 A!8) euals to

one million cycles of the system clock. & computer that operates at D44 !8Amegahert8) has D44 million clock cycles in one second.

GIGAHERT =GH)

Eiga is a prefix that stands for billion.Eigahert8 AE!8) euals to one billion

cycles of the system clock.*n relation with megahert8,2.K E!8 is eui#alentto 2KKK !8.

/or example, a microprocessor that runs at 3KK E!8 executes 3KK billion

cycles per second. This is what they are talking about if they say a computeris a 3.P E!8 machine. *ts clock rate is 3.P billion cycles per second.

E!8 is most often used as a measurement of a "C processor chip and power,with bigger numbers meaning more speed and higher price.

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PROCESSING SPEED

The system clock is one of the ma'or factors thatinfluence the computer speed. & C" with a higherclock speed can process more instructions per secondthan a C" with a lower clock speed. /or example, a2 E!8 C" is faster than a C" operating at KK !8.

The speed of the system clock affects only the C". *thas no effect on peripherals such as a printer or disk

dri#e.

MICROPROCESSOR SPEED

ne way of comparing the performance of personal computers is bycomparing their microprocessor speeds. icroprocessor speeds aredetermined by their clock speed and are usually expressed in gigahert8AE!8), billion of machine cycles per second.

/or example, a personal computer that is listed at 3.3 E!8 has a processor

capable of handling 3.3 billion machine cycles per second. & top speedpersonal computer can be much faster, with newer ones exceeding 4.K E!8.+irect comparison of clock is meaningful between identical microprocessor.

Thus, it is accurate to say that a "entium P running at 3.P E!8 is

approximately one-third faster than a "entium P running at 2. E!8.

SPEED AND PATH

The combination of speed and number of paths determines the totalprocessing speed or channel bandwidth. This is because different processorsoften use different architectures. /or this reason, a 2.P E!8 "entium Pperforms better than a 2.P E!8 "entium 4, but it is not as fast as a 2.P E!8"ower "C EP processor.