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Chapter1Introduction to

Computers

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Computers are electronic devices that can follow instructions to accept input, process the input and then produce information. It is a machine that manipulates data according to a set of instructions.

What are computers?

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HARDWARE

SOFTWARELook inside the computer

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Computers are made of

1. HARDWARE 2. SOFTWARE

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Hardware

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Hardware

The parts of computer itself (tangible objects ) including :

CPU (or Processor) and Primary memory (or Main Memory)

Input devices i.e the keyboard and mouse

Output devices Storage devices

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The Case (System Unit or System Cabinet)

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Hardware

1. Central Processing Unit (CPU)2. Input units3. Output units4. Memory (Main or Primary

Memory & Secondary or Auxiliary Memory)

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Components of a Computer System

Central Processing Unit (CPU)Central Processing Unit (CPU)

control unit (CU)

ArithmeticlogicUnit (ALU)

RAM

ROM

MemoryMemory

Inputunits

output units

AuxiliaryMemory

Data

Information/Knowledge

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Hardware Organization

motherboard

CPU

memory

hard drive

Input Devices ...

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Input Devices

• Translate data from form that humans understand to one that the computer can work with

• Most common are keyboard and mouse

Selector Buttons

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Examples of Input Devices

1. Keyboard (QWERTY keyboard, ATMs keyboard)ATM: automatic teller machine

2. Mouse 3. Scanner 4. Pre-storage Devise 5. Optical mark recognition (Light

Pin , Bar code scanners) 6. Microphone 7. Joystick .

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8. Point and Draw devices 9. Trackball10. Touchpad11. Touch screen 12. Magnetic stripes and smart

cars. 13. Digital Cameras

Examples of Input Devices(2)

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Hardware Organization

CPU

memory

hard drive

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RAM

Mother-Board (or Main Board)

CPU

ROM

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Hardware Organization

motherboard

CPU

memory

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Central Processing Unit (CPU)

• A specific chip or the processora CPU's performance is determined by the rest of the computers circuitry and chips.

• The Central Processing Unit (CPU) performs the actual processing of data

• The speed (clock speed) of CPU measured by Hertz (MHz)

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The CPU consists of :

Control Unit (CU) Arithmetic and Logical Unit

(ALU) Some Registers

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Central Processing Unit (CPU)Central Processing Unit (CPU)

Control Unit (CU)

Arithmetic Logic Unit (ALU)

This is CPU Only:

Registers

Central Processing Unit (CPU)

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The Control Unit (CU) :

coordinates all activities of the computer by:

• Determining which operations to perform and in what order to carry them out.

• The CU transmits coordinating control signals to other computer components.

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The ALU :consists of electronic circuitry to

perform:

• Arithmetic operations (addition, subtraction, multiplication and division)

• Logical operations (and, or, not, …) and to make some comparisons (less-than, equal, … etc.)

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Hardware Organization

motherboard

CPU

memory

hard drive

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Primary Memory

• Memory (fast, expensive, short-term memory): Enables a computer to store, at least temporarily, data, programs, and intermediate results.

• Two general parts:1.RAM 2.ROM

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RAM (Main Memory)• its a primary storage or random access memory

(RAM).• it temporarily holds data and programs for use

during processing (volatile)• Any information stored in RAM is lost when the

computer is turned off. • RAM is the memory that the computer uses to

temporarily store the information as it is being processed. The more information being processed the more RAM the computer needs.

• RAM consists of locations or cells. Each cell has a unique address which distinguishes it from other cells.

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Main Memory

Address Memory locations

1

2

3

n

Memory Cell

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Main Memory

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ROM: Read Only Memory

ROM is part of memory Programmed at manufacturing time Its contents cannot be changed by users It is a permanent store

Q: Mention some examples of ROM?A: (PROM & EPROM )

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Other Kind of Memory

PROM: Programmable Read Only Memory.

EPROM: Erasable Programmable Read Only Memory

Cache Memory Registers: not part of the main memory.

Q : Registers are part of “ …… ” ?

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Secondary StorageSecondary Storage

Stores data and programs permanently: its retained after the power is turned off

Examples•Hard Drive (Hard Disk)

Located outside the CPU, but most often contained in the system cabinet

•Floppy Disk•Optical Laser Discs

CD-ROM, CD-RW, and DVD

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Kinds of Disk DrivesDrives

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Common Secondary Media

• DiskettesDiskettes– Data represented as magnetic spots on

removable flexible plastic disks– Most common size is 3 1/2 inches, in a rigid

plastic case – Disk drive holds the diskette, reads or

retrieves the data and writes or stores data

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Common Secondary MediaCommon Secondary Media• Hard drive

– Data is represented magnetically as with diskettes

– Normally more than one rigid platterplatter in a sealed unit

– These disksdisks are not removablenot removable– Significantly more capacity and faster

operating than diskettes

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Hard drive

Common Secondary MediaCommon Secondary Media

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Hardware Organization

motherboard

CPU

memory

hard drive

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Optical Laser Discs• CD ROM & DVD’s

• Data is represented as pits and lands• Some kinds are read only (CD-ROM) and

some Kinds are rewritable (CD-RW)• Significantly more capacity and faster

operating than diskettes

Common Secondary MediaCommon Secondary Media

DVD: Digital Video Disk

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Disk sizeAmount of storageApproximate printed 8.5 x 11 inch pages

5.25 low density360 Kb180 pages

3.5 low density720 Kb360 pages

5.25 high density1.2 Mb600 pages

3.5 high density1.44 Mb720 pages

CD700 MBa small library

DVD8.5 GBa feature length movie

Common Secondary MediaCommon Secondary Media

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• tapes• Panasonic's LS120 3.5 inch diskettes3.5 inch diskettes• Iomega's Zip & Jazz disks• VCR tape (Video Cassette Recorder )• Flash USB disks• MMC (Multi Media Card )• SD

Common Secondary Media

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The benefits of secondary storage can be summarized as follows:

• Capacity. Organizations may store the equivalent of a roomful of data on sets of disks that take up less space

• Reliability. Data in secondary storage is basically safe, since secondary storage is physically reliable.

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• Convenience. With the help of a computer, authorized people can locate and access data quickly.

• Cost. It is less expensive to store data on tape or disk (the principal means of secondary storage) than to buy and house filing cabinets.

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Hardware Organization

CPU

memory

hard drive

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Output Devices

Pieces of equipment that translate the processed information fromfrom the CPU intointo a form that humans can understand.

CPUPr

oces

sed

info

rmat

ion

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Output Devices

MonitorsPrinters

Dot matrix printers Ink jet printers Laser printers

Sound Blasters (Sound Card By Creative Lab)

Controlling other devices

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Software

The instructions that tell the computer what to do

1. Application Software - helps end-users perform general purpose tasks

2. System Software - enables application software to interact with the computer

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System Software

The most important

System Software is the

Operating SystemOperating System

Examples of operating systems:Windows XP, DOS, Apple, UNIX

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System Software

• The software that controls everything that happens in a computer.

• Background software, manages the computer’s internal resources

Resources examples : CPU, RAM , I/O devices, …

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All hardware and software are under All hardware and software are under the control of the operating systemthe control of the operating system.

Among other things, the operating the operating systemsystem::1. Determines how valuable RAM is allotted to

programs.2. Performs tasks related to file management.3. Sets priorities for handling tasks.4. Manages the flow of instructions, data and

information to and from the processor (CPU).

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Examples ofExamples of Microcomputer Operating System Software

• DOS - original standard for IBM compatibles

• Windows - a graphical operating environment Windows VISTA, XP, millennium,

2000, 98, and 95

Continue …Continue …

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• Windows NT - for powerful workstations & networks

• OS/2 - competitor to Windows 2000• Macintosh Operating System• Unix - originally for minicomputers, now

used on microcomputers and Internet servers

QuestionQuestion: List some examples of operating systems ?

Examples ofExamples of Microcomputer Operating System Software

ContCont..

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Application SoftwareApplication Software

• Packaged - “off the shelf”, pre-written programs ( General purpose)

• Custom - written for an organization’s specific purpose (Special purpose)

Packaged Custom

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Application SoftwareApplication Software – Basic Tools – Basic Tools

• Word processors– example: example: Microsoft wordMicrosoft word

• Spreadsheets-- example: example: Microsoft ExcelMicrosoft Excel

• Database managers-- example: example: Microsoft AccessMicrosoft Access

• Graphics-- example: PhotoshopPhotoshop

Spreadsheets: Computer software that allows the user to enter columns and rows of numbers in a accounting book like format.

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Units of Measurements

Bit (Binary Digit)(takes two values: 1 or 0) Byte = 8 bits

KB (Kilo-byte) = 1024 bytes MB (mega-byte) = 1024 KB GB (giga-byte) = 1024 MB TB (Tera-byte) = 1024 GB

Remark: 1024=210

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1. Microcomputers

Four Kinds of Computers

3. Mainframe computers

2. Minicomputers

4. Supercomputers

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ComparisonComparison between the previous kinds of computers may made based on :

• Price• Processing Speed • Storage Capacity• Powerful• Single-user or Multi-user• Supporting hundreds (or thousands) of users simultaneously• Computer Size• Companies size• …etc.

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• Microcomputer =>Personal Computer => PC

• There are 3 types of the Microcomputers :1.Laptop2.Desktop3.Workstation

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• Personal Computer: A small, single-user computer based on a microprocessor.

• Workstation: A powerful, single-user computer. A workstation is like a personal computer, but it has : a more powerful microprocessor and, in general, a higher-quality monitor.

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Minicomputer, Mainframe, and Supercomputer

• Minicomputer: A multi-user computer capable of supporting up to hundredshundreds of users simultaneouslysimultaneously.

• Mainframe: A powerful multi-user computer capable of supporting many hundredshundreds oror thousandsthousands of users simultaneouslysimultaneously.

• Supercomputer: An extremely fast extremely fast computercomputer that can perform hundreds of millions of instructions per second.

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• Small enough for a desktop, but not easily portable

• Personal computers (PC’s) run general purpose software and are employed by a wide spectrum of users

Desktop Computer

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• WorkstationsWorkstations are powerful machines, running more advanced software, for technical, scientific, or data-intensive tasks

• These distinctions, however, are blurring

Desktop Computers Cont.

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• Easily transported from one place to another

Portable Computers

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Portable Computers

• Four categories1. Laptops2. Notebooks3. Sub-notebooks4. Personal Digital

Assistants (PDA)

Q: list all portable computer categories?

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PDA

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• Desk-sized• More processing speed

and storage capacity than microcomputers

• General data processing needs at small companies

• Larger companies use them for specific purposes

Minicomputers

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• Larger machines with special wiring and environmental controls

• Faster processing and greater storage than minicomputers

• Typical machine in large organizations

Mainframe Computers

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• The most powerful of the four categories

• Used by very large organizations, particularly for very math-intensive types of tasks

Supercomputers

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Supercomputers

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1- Store a large amount of data and information for a long period of time.

2- process data and information in high accuracy level .

3- Speed in processing data information.

4- Sharing of information / network.

Characteristics of Computers

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UnderstandingUnderstanding the difference between Data, Information and Knowledge:

ComputerComputerData

Knowledge

Information

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DataData: is the name given to basic facts such as names and numbers.

InformationInformation: is data that has been converted into a more useful or intelligible form.

KnowledgeKnowledge: arrangement of information and classifying information of the same type or the same topic.

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Data: are details of various types of transactions and details relating to specific situations, which are input to a data processing system (e.g. computer) for processing in a prescribed way. Examples of data relating to students are student-number, student-name and grades.

Data

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• e. g.

-2 4 0 -3 10 (datadata) | | sort \ / -3 -2 0 4 10 (informationinformation)

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Data

• Document files

• Worksheet files

• Database files

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Information

Information: the result of processing data.

Information: Must serve a useful purpose Must be of an acceptable level of accuracy Must be available at the right time Must be relevant to the enterprise, person,

… etc.

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Knowledge

• Putting a number of information with the same type or same topic would be a knowledge.

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Processing data produces information, and processing information produces knowledge.

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Computer VirusesComputer Viruses

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Computer Viruses

•A computer virus are small software programs that are designed to spread from one computer to another and to interfere with computer operation.

A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.

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Examples of Viruses

• Win32/Conficker• INF/Autorun• Win32/PSW.OnLineGames• n32/Agent

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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

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Types of Computer Viruses• Macro Viruses A macro virus, often scripted into common application

programs such as Word or Excel, is spread by infecting documents.

• Network Virusesrapidly spreads through a Local Network Area (LAN), and sometimes throughout the internet.

•Trojan HorsesThe Trojan virus once on your computer, doesn't reproduce, but instead makes your computer susceptible to malicious intruders by allowing them to access and read your files. Making this type of virus extremely dangerous to your computer's security and your personal privacy.

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Types of Computer Viruses

• Logic Bombsa piece of code that are inputted into a software system. When a certain and specific condition is met, such as clicking on an internet browser or opening a particular file, the logic bomb virus is set off.

• Companion Virusestakes advantage of MS-DOS. This virus creates a new file with typically the .COM extensions, but sometimes the .EXD extension as well.

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Types of Computer Viruses

• Boot Sector Virusesgenerally hide in the boot sector, either in the bootable disk or the hard drive. Unlike most viruses, this virus does not harm the files in the hard disk, but harm the hard disk itself.

• Multipartite Virusesspreaded through infected media and usually hides in the memory. Gradually, the virus moves to the boot sector of the hard drive and infects executable files on the hard drive and later across the computer system.

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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

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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

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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.

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Some tips that will help minimize your Some tips that will help minimize your vulnerability to viruses:vulnerability to viruses:

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.