1. Introduction To Computer System

2. 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:

6. Hardware

7. Input Devices (Used to accept data) 1. The Mouse A small hand-held device which has the shape of mouse. As it is moved a rolling bal on the underside transmits information to the computer which moves the cursor 2. The Keyboard The keyboard is still the commonest way of entering information into a computer 3. Tracker Balls an alternative to the traditional mouse and often used by graphic designers

8. Hardware Input Devices (Used to accept data) 4. Scanner A scanner allows you to scan printed material and convert it into a file format that may be used within the PC 5. Touch Pads A device that lays on the desktop and responds to pressure 6. Light Pens Used to allow users to point to areas on a screen 7. Joysticks Many games require a joystick for the proper playing of the game

9. Hardware

10. Output Devices 2. Printers There are many different types of printers. In large organizations laser printers are most commonly used due to the fact that they can print very fast and give a very high quality output. Kinds of Printers 1- Dot-Matrix. 2- Daisy Wheel 3- Inkjet 4- Laser 3. Plotters A plotter is an output device similar to a printer, but normally allows you to print larger images. 4. Speakers Enhances the value of educational and presentation products. 5. Speech synthesis Gives you the ability to not only to display text on a monitor but also to read the text to you

11. Hardware

12. Main Memory 1. Ram (Random Access Memory): where the system software and other applications are loaded. It is volatile memory. 2. Rom (Read Only Memory): it is a part of main memory that keeps instructions 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 data and instructions. It is faster than main memory. So it helps to increase the speed of the computer.

13. Hardware Data Representation in the memory Binary System is a numbering system that use only two digits 0 and 1. It’s base 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 is called 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)

14. 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 the disk. 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.

15. Hardware External Hard Disks Speed: Normally slower that internal disks, but more expensive versions offer the same performance as internal hard disks. Capacity: Same as internal disks. Cost: More expensive than internal disks.

16. Hardware Diskettes (Floppy Disks) Speed: Very slow! Capacity: Normally 1.44 Mbytes. Cost: Very cheap.

17. 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.

18. 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.

19. 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.

20. Software 2- Application Software All 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)

21. 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)

22. 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.

23. 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 CPU and 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.

24. 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

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

26. Computer Viruses

27. – 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)

28. Examples of Viruses n Monkes n ABC n Crabs n CIH

29. 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 help Anti-virus programs can help

30. 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)

31. 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.

32. 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

33. 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

34. 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

35. 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.

36. 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 periodically 6. 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:

37. 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.