Introduction To Computer System

Introduction

What is the Computer ?The Computer is a set of independent physical components and devices (Hardware), which have a specific job to do for each one and working together by Software to make up the computer system.

Computer perform three main operations:

Hardware

Hardware

Input Devices (Used to accept data)

1. The MouseA small hand-held device which has the shape of mouse.As it is moved a rolling bal on the underside transmitsinformation to the computer which moves the cursor

2. The KeyboardThe keyboard is still the commonest way of entering information intoa computer

3. Tracker Ballsan alternative to the traditional mouse and often used bygraphic designers

Hardware

Input Devices (Used to accept data)

4. ScannerA scanner allows you to scan printed material and convert it into a fileformat that may be used within the PC

5. Touch PadsA device that lays on the desktop and responds to pressure

6. Light PensUsed to allow users to point to areas on a screen

7. JoysticksMany games require a joystick for the proper playing of the game

Hardware

Hardware

Output Devices

2. PrintersThere are many different types of printers. In large organizations laserprinters are most commonly used due to the fact that they can print veryfast and give a very high quality output.

Kinds of Printers1- Dot-Matrix.2- Daisy Wheel3- Inkjet4- Laser

3. PlottersA plotter is an output device similar to a printer, but normally allows you toprint larger images.

4. SpeakersEnhances the value of educational and presentation products.

5. Speech synthesisGives you the ability to not only to display text on a monitor but also to readthe text to you

Hardware

Hardware

Main Memory

1. Ram (Random Access Memory): where the system software and otherapplications are loaded. It is volatile memory.

2. Rom (Read Only Memory): it is a part of main memory that keepsinstructions which make the computer work when turning it on.Those instructions can not be updated.

3. Cash Memory: it linked to the CPU and keeps the frequently used dataand instructions. It is faster than main memory. So it helps toincrease the speed of the computer.

Hardware

Data Representation in the memory

Binary System is a numbering system that use only two digits 0 and 1. It’sbase is 2. It is used by the computer system. (examples : convert from Bin to Dec & from

Dec to Bin systems ).

Measurements for memory capacity

1. Bit All computers work on a binary numbering system,i.e. they process data in one's or zero's. This 1 or 0 level of storage iscalled a bit.

2. Byte consists of eight bits.

3. Kilobyte (KB) consists of 1024 bytes (210 byte)

4. Megabyte (MB) consists of 1024 kilobytes (220 byte)

5. Gigabyte (GB) consists of 1024 megabytes (230 byte)

Hardware

Secondary Memory

Internal Hard Disks

Speed:Very fast!The speed of a hard disk is often quoted as "average access time" speed, measured in milliseconds. The smaller this number the faster thedisk.

Capacity:Enormous! Often in excess of 10 Gigabytes. A Gigabyte is equivalent to 1024 Megabytes.

Cost:Hard disks costs are falling rapidly and normally represent the cheapest way of storing data.

Hardware

External Hard Disks

Speed:Normally slower that internal disks, but more expensive versions offerthe same performance as internal hard disks.

Capacity:Same as internal disks.

Cost:More expensive than internal disks.

Hardware

Diskettes (Floppy Disks)

Speed:Very slow!

Capacity:Normally 1.44 Mbytes.

Cost:Very cheap.

Hardware

CD-ROM Disks

Speed:Much slower than hard disks. The original CD-ROM speciation is now given a value of 1x speed, and later, faster CD-ROMs are quoted as a multiple of this value.

Capacity:Around 650 Mbytes.

Hardware

DVD Drives

Speed:Much faster than CD-ROM drives but not as fast as hard disks.

Capacity:Up to 17 GBytes.

Cost:Slightly higher than CD-ROM drives.

Software

1- System Software (O.S.)It is special type of program that loads automatically when you

start your computer.

•Dos: Provides non Graphical User Interfaces (GUIs). It provides only

Blank screen to type the command (s).

•Windows: Provides Graphical User Interfaces (GUIs) such as Menu,

Commands, List Box, Tools … etc. So it depends on using mouse.

Software

2- Application SoftwareAll applications (programs) that may be installed in the computer system

if the user want them.

•Word processing (WinWord)

•Spreadsheet (Excel)

•database (Access)

•Presentation (PowerPoint)

•Web Designer (Front Page)

•Games (Fifa2000)

•Multimedia (Encarta)

•Desktop Publication (Adobe Photoshop)

Type of Computers

1- Main Frame:•Room Sized

•Expensive

•High Speed

•Very Powerful

•Large Storage Capacities

•They are used in Banks, Government department and large organization.

• Connected to a large No. of terminals (dumb or intelligent terminal)

Type of Computers

2- Mini Computers:•Do the same jobs as mainframe but in smaller scale

3- Personal Computers (PCs):•They are not expensive therefore they are very popular.

4- Laptop Computers :•It is small

•Briefcase Sized

•It has small screen and a small keyboard•It is powerful as PC but more expensive.

Computer Networks

1- Networked Computers•Computers are Linked together by cables so that files can be transferred.•If there is a server which stores the common files, then these files can be shared. Each computer has its own hard disk it can work independently.

2- Network Computer•A server is connected to small PCs called Client or terminal.•Client is a monitor with keyboard and small box which is contain CPUand Main memory.•It has not hard disk so it can not work independently.•A Client load applications and data from the server into memory•Any changes which are made will be made stored in the server.

Information Technology (IT)

A set of tools that are used to : receive, process and transmit

information in an electronic form through computers. These

forms can be text, sound, picture or video

Computer Uses

1- Supermarkets: Use a bar code reader.2- Libraries: Use computers to search for books; to record bookslending and return ….3- Banks: Enable customers to access their accounts via ATM.4- Plastic Cards: Used in computer system to facilitate customerslife (mobile, telephone and credit cards)5- Electronic Commerce: Uses Internet in business forpurchasing, payment, or reservations.6- Touch Screens: Allow unskilled customers to accessinformation easily.7- Hospitals: Use computers to store records of patients and tohelp in the diagnosis and analysis of the treatment.8- Cars: Computers are used to display maps and giveinstructions to the driver.

Computer VirusesComputer Viruses

Computer Viruses

– A computer virus is an application program designed and written to destroy other programs.

– It has the ability to: Link itself to other programs Copy itself (it looks as if it repeats itself)

Examples of Viruses

Monkes ABC Crabs CIH

Viruses and Virus Protection

A virus program– Infects programs, documents,

databases and more …– It is man-made– It can hide and reproduce– It can lay dormant (inactive)

and then activate

Anti-virus programs can helphelp

A variety of highly contagious “viruses” can spread from computer to computer, much the way biological viruses do among human beings. Just as a virus can infect human organs, a

computer virus can infect programs and databases. It can also hide duplicates of itself within legitimate programs.

Viruses and Virus Protection (2)

Viruses and Virus Protection(3)

These viruses, which are programs, reside on and are passed between magnetic disks.

Most people who write and circulate virus programs fall into two groups.

1. The first group uses viruses to show off for their peers.

2. The second, and far more dangerous group, creates viruses with malicious intent.

Types of Computer Viruses

Macro viruses – Written into the program macro– Shuts down functions

Worm– A program that makes copies of itself – It will interfere with normal operations

Sources of Computer Viruses

Three primary sources– The Internet

Via downloads and exchanges

– Diskettes Exchanging disks

– Computer networks Can spread from one network to

another

How do you know if you have a virus?

Lack of storage capability Decrease in the speed of executing programs Unexpected error messages Halting the system

Virus Protection

• The software package distributed with new PCs always includes an antiviral program. The best way to cope with viruses is to recognize their existence and use an antiviral, or antivirus program.

1. Delete e-mails from unknown or suspicious, untrustworthy (unreliable) sources, especially those with files attached to an e-mail.

2. Never open a file attached to an e-mail unless you know what it is, even if it appears to come from a friend.

3. Download files from the Internet only from legitimate and reputable sources.

4. Update your antivirus software at least every two weeks as over 200 viruses are discovered each month.

5. Backup your files periodically6. Traditionally virus protection has been at the PC or

client level. However, this may change as companies look to network and Internet service providers for more services.

Some tips that will help minimize your vulnerability to viruses:

Computer Ethics

You shall not use a computer to harm other people. You shall not snoop around in other people's computer files. You shall not use a computer to steal. You shall not use other people's computer resources without

authorization or proper compensation. You shall always use a computer in ways that show

consideration and respect for your fellow humans.