Chapter One Information Technology in Perspectiveto+computers.v7+(1).pdf · Introduction to Computers. By: Rami Hodrob and Ra’fat Amarneh. 1 Introduction to Computers Chapter One

Introduction to Computers. By: Rami Hodrob and Ra’fat Amarneh. 1

Introduction to Computers

Chapter One

Information Technology in Perspective

Computers are everywhere: at work, at school, and at home. People use all types and sizes of computers.

While some computers sit on top of a desk or on the floor, mobile computers and mobile devices are small

enough to carry. Mobile devices, such as many cell phones, often are classified as computers.

Computers are a primary means of local and global communication for billions of people.

Consumers use computers to correspond with businesses, students with classmates and teachers,

and family members with friends and other family members.

People use computers to share photos, drawings, documents, calendars, journals, music, and videos.

Through computers, society has instant

From the computer, you can make a telephone call, meet new friends, share opinions or life stories, book

flights, shop, fill prescriptions, file taxes, take a course, receive alerts, and automate your home.

Computer is an Electronic device operating under the control of instructions stored in its own memory.

Information Technology= Information +technology

• Definition of Technology:

The application of scientific knowledge to the practical aims of human life.

Technology is people using knowledge, tools, and systems to make their lives easier and better

• Science deals with the study of phenomena in the natural world (physics, chemistry, geology,

• Science deals with "understanding" while technology deals with "doing“

Knowledge chain:

data --- Information --- Knowledge

Data

• Raw facts, a collection of facts from which conclusions may be drawn with different forms such as:

text, numbers, images, or thoughts.

Information

• Processed meaningful data as a result of processing, manipulating and organizing data. Information

leads to knowledge

Knowledge is the result of perception and learning and reasoning.

Information Technology (IT) refers to the integration between computer Technology and Information

processing. The implementation of different branches of technology(hardware, software, firmware, and

procedure) in information processing (acquisition, storage, manipulation, management, control, display,

switching, interchange, transmission, and reception of data).


Information Processing Cycle: The series of input, process, output, storage and communications.

Computers process data (input) into information (output). Computers carry out processes using instructions,

which are the steps that tell the computer how to perform a particular task. A collection of related instructions

organized for a common purpose is referred to as software. A computer often holds data, information, and

instructions in storage for future use.

Common Computer Hardware Devices


Computer system:

Is the integration of physical components called Hardware and none physical components called Software.

1. Hardware (H.W.): which are the touchable components and electronic devices (The physical parts of

the computer). Including: the Central processing Unit (CPU), Memory and peripheral devices as:

Keyboard, mouse, screen,…

2. Software (S.W.): The programs that run over the computer.

Hardware (H.W.):

Hardware has the following basic components:

1. Input Unit:

Devices that enter data to the computer

Examples: keyboard, mouse, scanner, camera,…………..

2. Output Unit:

The devices, that output information from the computer after processing data.

Examples: screen, printer, speaker ………...

3. System Unit

The system unit is a case that contains the electronic components of the computer

that are used to process data. It includes most of the followings:

A. Motherboard: The circuitry of the system unit usually is part of or is connected to a circuit board.

Two main components on the motherboard are the processor and memory.

The processor, also called a CPU (central processing unit).

Central Processing Unit (CPU). Memory (RAM, ROM)

Which are mainly the processor and some of the devices on the motherboard (main board).

B. CPU is the electronic component that interprets and carries out the basic instructions that operate the

computer. CPU has three components:

1- CU (Control Unit):

Controls the flow of input/output.

Used to ftch and decode instructions.

2- ALU (Arithmetic Logic Unit):

Does the logical and arithmetic operations.

3- Registers:

Very high speed storage arrears.

C. Memory (RAM & ROM, cache):

RAM is used to store programs and other data waiting for processing. Memory consists of electronic components that store instructions waiting to be executed and data needed by those

instructions. Although some forms of memory are permanent (such as ROM), most memory keeps data and

instructions temporarily (RAM), which means its contents are erased when the computer is shut off.

D. Storage Unit: devices and media that is used to store data. Such as: Hard Disk, CDs, floppies, flash

memory and tapes.

Storage Unit: consists of two parts:

1. Primary Storage:

RAM (Random Access Memory): is a volatile memory (Data will be lost when turn off the

computer).


ROM (Read Only Memory): is a non volatile memory. (it holds the instructions that boot

(startup) and prepare a computer for use).

2. Secondary Storage:

Is a part of memory of a computer where programs and data are stored when not in use, like (hard

disk, floppy disk, CD, flash memory…).

Software (S/W.): Computer programs.

Program consists of a series of instructions that tells the computer what to do and how to do it.

Types of software:

1) System Software: consists of the programs that control or maintain the operations of the computer and its

devices. System Software is needed to operate the computer such as Operating system (Programs that control

the operations of the computer, serves as the interface between the user, the application software, and the

computer’s hardware. Used to configure and setup the computer options).

A. Operating Systems (OS): is a program that acts as an intermediate between a user of a computer and

the

computer hardware.

OS is used for Managing operations, controlling the computer systems, implementing the security, &

manages the secondary storage & others.

Examples of O.S.: MS DOS (Microsoft Disk Operating System), windows (and its family: win95, win98,

win2000, NT2000 and finally win 7 and …), UNIX.

Progress of OS:

Batch processing: Only one job is done at the computer at a time.

Interactive processing: computer could respond to users while in processing.

Real time processing: Data processing keeps pace with tasks at hand so results are part of the

transactions.

Multi user system: many users use the same computer at the same time. These systems called time

sharing systems. It is consisted of one main computer connected to several terminals which is

called LAN with PC's.

Multitasking system: Many tasks are done at the same computer at the same time.

B. Utilities are Programs allow the user to perform maintenance-type tasks usually related to managing a

computer, its devices or its programs such as antivirus and disk management and Pc tools

2) Applications Software: enables the users to do special tasks (Programs designed to make users

more productive and/or assist them with personal tasks).


Examples of application software:

Communications and Internet. All programs that manages the network system and that

connects us to the web like web browsers, chatting, Email programs, dial up… etc.

Multimedia and graphics, voice and video, examples: paint shop, Adobe photo shop...

Office applications:

- Word processors (MS word, word perfect)

- Spread sheets (MS Access, Quattro pro)

- Desktop publishing (MS publisher)

- Project planning (MS project)

Home software: like Home Medical Advisor.

Games.

Educational and research software CAD (Computer Aided Design) and CAM and CBT

(Computer Based Training).

Databases are environment to store and retrieve data and to manipulate and connect data to

extract information. Examples on Database Management Systems are Oracle SQL, server2000,

Informix, access.

Web application: A software application that obtains information from the Web

A programmer, sometimes called a computer programmer or developer, is someone who develops software or

writes the instructions that direct the computer to process data into information. Programmers use a

programming language or program development tool to create computer programs. Popular programming

languages include C++, Java, JavaScript, Visual C#, and Visual Basic.


Computers are classified into categories according to their computing capabilities:

1. Personal computers (PC): is a computer that can perform all of its input, processing, output, and

storage activities by itself. A personal computer contains a processor, memory, and one or more input,

output, and storage devices. Personal computers also often contain a communications device.

The CPU is on a single chip (one CPU).

Used at homes, schools.…

Is a single-user.

Two types of personal computers are desktop

computers and notebook computers.

A mobile computer is a personal computer you can carry from place to place. Similarly, a mobile device is a

computing device small enough to hold in your hand.

A notebook computer, also called a laptop computer, is a portable, personal computer often designed to fit

on your lap.

Tablet PC is a special type of notebook computer that allows you to write

or draw on the screen using a digital pen.


smart phone is an Internet-enabled phone that usually

also provides personal information management

functions and allows you to send and receive e-mail

messages and access the Web.

PDAs A PDA (personal digital assistant)

provides personal information management

functions such as a calendar, an appointment

book, an address book, a calculator, and a notepad.

2. Server: controls access to the hardware,

software, and other resources on a network and

provides a centralized storage area for programs,

data, and information.

3. Mainframes: is a large, expensive, powerful

computer that can handle hundreds or thousands

of connected users simultaneously. Mainframes

store tremendous amounts of data, instructions,

and information. Most major corporations use

mainframes

for business activities.

High storage capacity.

High-speed processing.

Used in commercial establishments.

Multi-user.

4. Workstations:

Is a middle-range machine between a mainframe and a PC.

Used for scientific & engineering applications.

5. Supercomputers: is the fastest, most powerful

computer — and the most expensive. The fastest

supercomputers are capable of processing more than

one quadrillion instructions in a single second. It can

store more than 20,000 times the data and information

of an average desktop computer.

Very large storage.

Very high speed.


Contains many CPU's & called Parallel computers.

Used in technical areas that deals with large numbers such as in weather forecasting.

6. Embedded computer is a special-purpose computer that functions as a component in a larger product. Embedded

computers are everywhere - at home, in your car, and at work.

Information system comprises of hardware, software, data, people, and procedures.

Doctors, nurses, technicians, and othermedical

staff use computers and computerized devices to

assist with medical tests.

This handheld navigation device gives users

turn-by-turn voice-prompted directions to a

destination.


Chapter 3

Inside the Computer

Analog and Digital

Analog signals are continuous wave forms where there is no abrupt change.

Example: everything in nature acts analog like our voice.

Digital signals: discrete signals where everything is described in two levels (high and low) (0 and 1).

Example: computers are digital devices.

When sound is saved in computer, it has to be converted from analog to digital (digitized).

Binary Bits

In order to run S.W. applications, computers must translate S.W. code into binary form and then must

translate it from binary form into a language you can understand. Computers operate with electronic switches

that are either "on" or "off", corresponding to 1 or 0.

Computers don't think in the decimal number system as humans do, because electronic devices are structured

in such a way that binary numbering is natural – computers have to translate in order to use decimal

numbering. Computers can only understand and process data that is in a binary format, which is represented

by 0s and 1s. These 0s and 1s represent the two possible states of an electronic component and are referred to

as binary digits (bits).

Binary codes: ASCII & EBCDIC – the special coding scheme (The binary number representation of many keyboard and

control characters is shown in the ASCII)

ASCII: American Standard Code for Information Interchange.

ANSI: American National Standards Institute.

EBCDIC: Extended Binary Coded Decimal Interchange Code.

Example:

EBCDIC representation of word Mom:

11010100 10010110 10010100

M o m

Unicode

The ASCII code is 7 bits (128 characters) (27) is sufficient for English language (see table below).


The ANSI code is 8 bits (256 characters) (28).

But what is about the other languages?

The Unicode is 16 bit (65536 characters) (216

) is the new coding

system, which includes most the languages of the world.

Bits are binary digits; they are either 0s or 1s. In a computer they are represented by the presence or absence

of electrical charges.

Example:

Binary 0 might be represented by 0 volts of electricity (0 = 0 volts).

Binary 1 might be represented by +5 volts of electricity (1 = +5 volts).

A group of 8 bits equal 1 byte, which then can represent a single character of data, as in an ASCII code. Also,

for computers, 1 byte represents a single addressable storage location.

The Base 10 (Decimal) system

A number system consists of symbols, and rules for using those symbols; many number systems exist. The

number system most frequently used, and the one with which you are probably most familiar, is the decimal,

or Base 10 number system. It is called Base 10 because it uses ten symbols, and combinations of them, to

represent all possible numbers. The digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9, make up the Base 10 system.

A decimal number system is based on powers of 10. Each symbol, or digit, represents the number 10 (base

number) raised to a power (exponent), according to its position, and is multiplied by the number that holds

that position. When you read a decimal number from right to left, the first position represents 100 (1), the

second position represents 101 (10 x 1= 10), the third position represents 102 (10 x 10 x 1=100), 10

6 (10 x 10

x 10 x 10 x 10 x 10 x 1= 1,000,000).

Example:

2134 = (2x103) + (1x10

2) + (3x10

1) + (4x10

0)

The Base 2 (Binary) system:

Computers recognize and process data using the binary (Base 2) numbering system. The binary system uses

only two symbols – 0 and 1 – instead of the ten symbols used in the decimal numbering system. The position,

or place, of each digit represents the number 2 – the base number – raised to a power (exponent), based on its

position (20, 2

1, 2

2, 2

3, 2

4, etc.)

Example:

10110 = (1 x 24) + (0 x 2

3) + (1 x 2

2) + (1 x 2

1) + (0 x 2

0)

= (1 x 16) + (0 x 8) + (1 x 4) + (1 x 2) + (0 x 1)


= (16 + 0 + 4 + 2 + 0)

= 22.

If you read the binary number (10110) from left to right, you see that there is a 1 in the 16s position, a 0 in the

8s position, a 1 in the 4s position, a 1 in the 2s position, and a 0 in the 1s position, which adds up to decimal

number 22.

Conversion from Decimal to Binary:

There are two basic ways to convert decimal numbers to binary numbers. One of them is called the remainder

method. This method uses repeated divisions using the base number of the system. In this case it is Base 2.

Example:

Convert the decimal number 192 to a binary number.

192/2 = 96 with a remainder of 0








Write down all the remainders, backwards, and you have the binary number 11000000.

Converting Binary numbers to Decimal numbers:

You can convert binary numbers to decimal numbers by multiplying the binary digits by the base number of

the system – Base 2 – raised to the exponent of its position.

Binary Decimal Multiply by power of 2

Example 1:

Convert the binary number 01110000 to a decimal number. (Note: Work from right to left. Remember that

anything raised to the 0 power is 1; therefore 20 = 1.)

01110000 = 0 x 20 + 0 x 2

1 + 0 x 2

2 + 0 x 2

3 + 1 x 2

4 + 1 x 2

5 + 1 x 2

6 + 0 x 2

7

= 0 + 0 + 0 + 0 + 16 + 32 + 64 + 0

= 112

Example 2:

100101 ????? 1*20 + 0*2

1 + 0*2

2 + 1*2

3 +0*2

4 + 1*2

5 = 37

Binary base 4

Since base 2 is implied in base 4 as a power of 2, every 2 binary bits form 1 digit of base 4 starting from the

right side.

11 01 11 01 10 11 11 00 01(2)

3 1 3 1 2 3 3 0 1(4)

(Bits)


base 4 binary :

The reverse way: Each digit is equivalent to 2 bits

3 1 3 1 2 3 3 0 1(4)

11 01 11 01 10 11 11 00 01(2)

Base 2 base 8:

every 3 binary bits equivalent to 1 digit base 8

Base 2 Hexadecimal:

Every 4 binary bits equivalent to 1 hex digit.

11 0111 0110 1111 0001(2)

3 7 6 F 1(10)

Unit Definition Bytes Bits Examples

Bit

(b)

Binary digit,

A 1 or 0 1 bit 1 bit On/off; Open/closed

+5 Volts or 0 Volts

Byte

(B)

Usually 8 bits 1 byte 8 bits Represent the letter "X" as

ASCII code

Kilobyte

(KB)

1 Kilobyte

= 1024 byte 1000 byte

= 210

byte

8,000

bits Typical Email = 2 KB

10 - page report = 10 KB

Early PCs = 64 KB of RAM

Megabyte

(MB)

1 Megabyte

= 1024 Kilobyte

= 1,048,576 bytes

1 million bytes

= 220

byte

8

million

bits

Floppy disks = 1.44 MB

Typical RAM = 32 MB

CDROM = 650 MB

Gigabyte

(GB)

1 Gigabyte

= 1024 Megabytes

= 1,073,741,824 bytes

1 billion bytes

= 230

byte

8

billion

bits

Typical Hard Drive = 4 GB

Terabyte

(TB)

1 Terabyte

= 1024 gigabytes

= 1,099,511,627,778

bytes

1 trillion bytes

= 240

byte

8

trillion

bits

Amount of data theoretically

transmittable in optical fiber

in one second

Example1:

How many Bytes in 15 Kbytes?

15 KB = 15 * 210

= 15 * 1024 = 15360 Bytes.

Example2:

How many Bits in 25 MB?

25 MB = 25 MB * 1024 *1024 * 8

= 25 MB * 220

* 8

=209715200 Bits.


Personal Computer: The PC System Unit:

The computer System Unit contains:

• The motherboard: main electronic components.

• The power supply: Transformer to provide computer with power.

• The drives:

CD drive

Hard disk

Floppy disk


The Motherboard of a PC is the main circuit board that provides a path of communication between the

processor, memory, and other devices (peripheral).

• Carrier of main computer components

• provides each component with power and transportation bus

• Holds the following elements

• One or more microprocessor.

• A basic input/output system chip (BISOS) or ROM.

• Memory (RAM) slots.

• The chipset.

• The level 2 cache.

• The expansion slots (graphics sound, video, network . . .).

• Peripheral component interconnects (printer, mouse, keyboard, . . .).

• CMOS or NVRAM unit.

• IDE or EIDE disk controllers.

Peripheral device is a device that is not a part of CPU.

Peripheral devices can be external such as (a mouse, keyboard, printer, monitor, external drive or scanner) or

internal such as (a CD-ROM drive, CD-R drive or internal modem).

The motherboard chipset controls the flow of information between system components. It determines the type

of the processor and memory.

Attached to the motherboard are:

Microprocessor.

Electric circuitry

Memory chips

Expansion slots to add expansion boards such as modems, soundcards, Network Interface Cards and

others.

Microprocessor (CPU – Central Processing Unit):

Control Unit (CU): It has three primary functions:

o Read and interpret program instructions.

o To direct the operation of the internal processor components.

o To control the flow of programs and data in and out of RAM.

Arithmetic Logical Unit (ALU):

Performs all computations (addition, multiplication, subtraction…) and logical operations (AND, OR,

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NOT…).

Registers:

High-speed storage area within the CPU. All data must be represented in a register before it can be

processed. For example, if two numbers are to be multiplied, both numbers must be in registers, and

the result is also placed in a register. (The register can contain the address of a memory location where

data is stored rather than the actual data itself.)

There are three major features that distinguish processor (CPU)

1. Word size:

Word is a number of bits that are handled as a unit during processing or when transferred over the

system Bus.

2. Processor speed: The pace of the system clock is called the clock speed, and is measured in gigahertz

(GHz) (The speed in Mhz or Ghz is the number of pulses generated per second.)

- Mhz is used to measure the speed of the personal computers (PC's).

1 Mhz = 1 million cycles per second.

- Million Instructions Per Second (MIPS): used for workstations and mainframes.

- Floating-Point Operations Per Second (FLOPS): used for supercomputers.

3. Memory capacity:

Measured in Kilobyte or MB or GB…

Most processor chips nowadays are multi-core processors. A multi-core processor is a single chip with two

or more separate processor cores. Two common multi-core processors are dual-core and quad-core.

Machine Cycle:

For every instruction, a processor repeats a set of four basic operations, which comprise a machine cycle :

(1) fetching, (2) decoding, (3) executing, and, if necessary, (4) storing.

Fetching is the process of obtaining a program instruction or data item from memory.

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Memory: consists of electronic components that store instructions waiting to be executed by the processor,

data needed by those instructions, and the results of processing the data.

Main Memory:

Random Access Memory (RAM) (Volatile).

Memory chips are installed on a thin plat (printed circuit board) that comes in two ways:

Single In-Line Memory Module (SIMM)

- 32 bit wide bus

Dual In-Line Memory Module (DIMM)

- 64 bits wide bus.

There are two types of RAM:

SDRAM (Synchronous Dynamic RAM).

- enabling data transfer at more than twice the speed of RAM.

RDRAM (Rambus Dynamic RAM).

- which is six time faster than SDRAM.


Cache Memory:

Is a random access memory (RAM) that a computer microprocessor (CPU) can access more quickly that it can

access regular RAM.

The CPU processes data looks first in cache memory, and if finds the data there, it does not have to do the

more time-consuming reading of data from larger memory (RAM).

Bus:

Is a collection of wires through which data is transferred from one part of the computer to another?

There are generally two buses within a computer:

Internal buses: connect internal components to the CPU and main memory

Expansion buses (input/output busses): connects expansion boards to the CPU and boards, (allows

various motherboard components (USB, serial, and parallel ports, hard drives, CD-ROM and CD-RW

drives, etc.) to communicate with one another. It is mainly used to add new devices using what are

called expansion slots connected to the input/output bus.)

All buses consist of two parts:

The address bus: Transfers information about where data should go.

The data bus: Transfers instructions coming from or going to the processor. (Transfers actual data).

The control bus: Transports orders and synchronization signals coming from the control unit and

traveling to all other hardware components.

The number of bits that can be transmitted at a time determines the size of a bus known as its width, its

important because it determines how much data can be transmitted at one time.

For example, a 16-bit bus can transmit 16 bits of data, whereas a 32-bit bus can transmit 32 bits of data.

Each Bus has a clock speed measured is Mhz. (1 Mhz = 1 million cycle/second)

Types of Expansion buses:

The Industry Standard Architecture

(ISA). Oldest and slowest.

The Enhanced ISA bus (EISA) buss.

Peripheral Component Interconnect

(PCI) bus.

Accelerated Graphics Port (AGP).

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The PCs and their compatibles are classified according to their processors (mainly Intel microprocessor) as

follows:

Name Date Transistors Microns Clock

Speed

Data

Width

MIPS

8008 1974 6,000 6 2 MHz 8 bits 0.64

8086 1979 29,000 3 5 MHz 16 bits,

8-bit

0.33

80286 1982 134,000 1.5 6 MHz 16 bits 1

80386 1985 275,000 1.5 16 MHz 32 bits 5

80486 1989 1,200,000 1 25 MHz 32 bits 20

Pentium 1993 3,100,000 0.8 60

MHz

32 bits,

64-bit

100

Pentium II 1997 7,500,000 0.35 233

MHz

32 bits,

64-bit

~300

Pentium III 1999 9,500,000 0.25 450

MHz

32 bits,

64-bit

~510

Pentium 4 2000 42,000,000 0.18 1.5

GHz

32 bits,

64-bit

~1,700

A dual-core processor is a single chip that contains two separate processors

A multi-core processor is a chip with two or more separate processors


Ports:

Is the interface between the computer and the out world

Types of ports:

1. Serial Port: allows the serial transmission of data:

One bit at a time, connecting modem…

2. Parallel Port: allows the parallel transmission of data:

Several bits at a time, connecting printer…

3. Small Computer System Interface (SCSI):

Faster data transmission that serial and parallel.

4. Universal Serial Bus (USB):

High speed device interface.

5. Mouse and keyboard ports:


Basic Personal Computer System

Modern Personal Computer:


Chapter 4

Mass Storage and files

Programs and information are stored in RAM and permanent mass storage such as magnetic disks and tapes.

A file is a collection of information that has a name called filename. Each file name has an extension that

distinguishes file types. So the filename is on the form fname.ext example: letter.doc is a document file

A folder (or directory) is a special file used to organize other files. I mean programs and information files

are placed in folders (directories).

Programs and information (text, image, audio, video) are stored:

Temporarily in RAM

Permanently in Mass Storage (magnetic disk and tape)

Mass storage means, the permanent storage media.

Data are retrieved from mass storage and stored temporary in RAM.

Types of mass storage devices and media:

1. Magnetic disk.

2. Magnetic Tape.

3. Optical Laser Disk.

Data is stored on the media as files.

File is a collection of information that has a name called file_name and each file name has an extension that

distinguishes the file type. File_name . Extension_name

Example: rafat . txt

Types of files: (most popular file types)

1. ASCII file: a file that consists of ASCII characters, no images, equations and special formats. The

name format is *.txt

2. Data file: Contains data organized into records. Records are composed of fields each of wich

contains one item of information. For example the MS Access data file name has the format

*.mdb. The extension depends on the software used to create the file.

3. Document file: can contain texts, images, and other formatted text. The most common is the MS

Word document *.doc

4. Spreadsheet file: contains rows and columns of data. For example MS Excel files *.xls


5. Web page file: Compatible with the Internet browsers. *.htm or *.html. The extension html stands

for Hyper Text Marking Language.

6. Source program file: contains program instructions. In C language *.c in Fortran language the file

name is on the format *.f

7. Executable program file: To execute (run) a computer program, one must be compile it by a

computer language compiler like C compiler, Pascal Compiler, and others. The Compiler encodes,

checks the program for errors (grammar errors), and produces the executable program in the

machine language. The executable file *.exe can be executed to produce the results.

8. Graphic file: Contains digitized images (the binary code of an image). There are different formats

of such files, among them, the bmp, gif, and jpeg files.

9. Audio file: contains digitized sound. Examples wav and MP3 files. There are several software

available to compress audio files to save space and to be able to send and receive them over the

internet. For example, real audio files *.ra and other formats are used for live broadcast over the

internet.

10. Video file: contains digitized video frames and when played (25 frames/sec for PAL system)

produces motion video. For example the Video Interleave (AVI). A software and hardware can be

used to compress video file to produce smaller video files. One the latest technology in video

compression is the Moving Pictures Experts Group (MPEG).

Examples of Types of files

1. ASCII file (Text file): a file that consists of ASCII characters, no images, no equations and no special

format. Example: *.txt (Notepad program)

2. Data file: That contains data organized into records. Example: *.mdb (MS-Access program)

3. Document file: That contains text, images and other formatted text. Example: *.doc (MS-Word program)

4. Spread sheet file: That contains rows and columns of data. Example: *.xls (MS-Excel program)

5. Web file: That can be opened by internet browsers. Example: *.htm (Internet explorer program)

6. Source program file: That contains program instructions. (source code of program) Example: *.cpp (C++ program)

7. Executable program file: To execute (run) a computer program. Example: *.exe , *.com

8. Graphics file: That contains digitized images (the binary code of the image). Example: *.bmp , *.gif

9. Audio file: That contains digitized sound. Example: *.wav , *.mp3

10. Video file: That contains digitized video frames and when played produced motion video.


Example: *.avi , *.mpeg

There are several software available to compress audio, video and graphics files to save space and to be able

to send and receive them over the internet.

Magnetic Disks

Two types of magnetic disks: Interchangeable and fixed (hard) hard disks. The disk is the media were the data

is stored and the drive is the device that reads/writes the disk. Binary digits are represented by the presence

and absence of electronically magnetized dots.

A. Interchangeable magnetic disks. There are several types. Among them:

1. The floppy disk or the diskette. It is a 3.5” disk. The standard capacity is 1.44 MB for high-

density diskettes.

2. The super disk has the same physical size as the floppy but its capacity is 120 MB. The density

is different from the floppy and it needs special drive. The super drive can read a floppy disk

but the floppy drive can’t read super disks.

3. The zip disk has a capacity of 100 MB-250 MB and it needs a special zip drive.

Most PC’s comes with a floppy drive.

B. The hard disk.

Two features distinguish hard disks from each other: the capacity and the speed of transferring data

from and to the hard disk. Usually hard disks are fixed in the system unit, but it can be a separate unit.

Also you can buy a hard disk frame with a drawer and install it in the system unit then you can add the

hard disk to the drawer and when done take back your hard disk. This is convenient for people who

work on sensitive data where the hard disk can be placed in a safe place.

There are two types of Hard Disks:

1. Permanently installed hard disks: The capacity varies. The most common in the local market is

hundreds of GBs. It contains:

i. Several platters (disks) where data can be recorded on both sides of each platter.

With 4 platters, there 8 surfaces for recording.

Example: 4 platters = 8 surfaces, data stored in 6 surfaces (8 – 2) = 6.

ii. Flying read/write heads for each surface mounted on access arms. The flying

heads are so close to the surface that a particle of smoke will not fit between the

head and the surface. Access arms works together. They move as a one unit.

2. Interchangeable hard disks: as an example is the Jaz Cartridge which is similar to a video tape.

A Jaz drive reads and writes to the Jaz cartridge. The capacity is over 1 GB.

The smallest and lightest hard-disk drive is the Microdrive by IBM. The platter fit into an egg. The

capacity is 340MB. It is perfect for palmtop PC’s.

Disk: is the media were the data is stored.

Drive: is the device that read / write the disk.


Magnetic Disk Organization:

Data and programs are stored on interchangeable disks and hard disks in similar way.

The surface is formatted as follows:

Magnetic Disk Organization: Data and programs are stored on interchangeable disks and hard disks in similar way. The surface is formatted

as follows:

a. Tracks are concentric (circles with the same center). The number of tracks varies from one disk to

another. It can be as few as 80 tracks for diskettes and in thousands for hard disks. The number of

Tracks Per Inch (TPI) is used to measure the spacing of tracks.

b. A cylinder is the same-numbered tracks on each recording surface

c. Tracks are divided into sectors. The sector is the smallest unit that can be accessed on a disk. The

number of sectors depends on the density of the disk. Typically, the storage capacity of each sector in

a track is 512 bytes. A bad sector is a sector that can’t be accessed.

d. A cluster is a number of adjacent sectors. Typically the cluster size ranges from 8 to 64 sectors. For

512-bytes sectors, the size of a cluster ranges from 4096 bytes = 4 Kbytes to 32,768 bytes = 32

Kbytes.

The cluster is the smallest unit of disk space that can be allocated to a file. Therefore, every file saved

to the disk takes up one or more clusters. Each cluster has a number or address. The number of the first

cluster allocated to a file is the disk address of the file. The address gives the physical location of the

file on the disk. In general, more than one cluster is allocated to the same file (depends on the size of

the file). Clusters allocated for the same file need not be adjacent but must be linked. When write to a

file, the write head points to the disk address of the file and writes the first cluster, then it searches for

another cluster that is not allocated to other files, records the address of the next cluster at the end of

the first one and so on until the all file is written. To read the file, the read head, controlled by the

program, points to the disk address of the file and reads the first cluster and the address of the next

cluster allocated to the file then it points to the address of the second cluster. The process is continued

until the last cluster, which shows that no more clusters are allocated to the given file.

Sometimes, the operating system marks a cluster as being used even though it is not assigned to any

file (usually as a result of power interruption). Such a cluster is called lost cluster. There are utilities

that search for lost clusters and mark them for use. You can try Scandisk in windows: start –

accessories – system tools – scan disk

e. The File Allocation Table (FAT)

This is a table where information about files stored. When a request for a particular file is made, the

operating system (like windows) searches the FAT for the disk address of the file and then perform the

task as explained above.

In Windows 95, 16-bit addresses are used and the FAT is called FAT16. Windows 98 and 2000

FAT32 is used that means 32-bit addresses. FAT32 increases the number of bits used to address

clusters and allows more clusters to be addressed (have unique addresses) which results in smaller

clusters. A 33KB file being stored on a disk with 32KB clusters takes up 2 clusters = 64KB. 31KB in

the second cluster are unused. If the disk has 16KB clusters, the 33KB file will take up 3 clusters or


3x16 = 48KB with 15KB of unused space. Now, Large clusters may improve the overall system

performance because files consist of less number of scattered clusters but with large portion of unused

disk space. On the other hand, smaller clusters save disk space but can slow the system.

f. Defragmentation: Rearranging Clusters to Enhance performance:

Due to frequent use of files (create, modify, move, and delete), a single file that takes up several linked

clusters that can be scattered all over the hard disk. The linked clusters of a file are called

fragments. For example a 5 MB file may require thousands of linked clusters that can be scattered

all over and the read/write head must move many times across the surface of the disk to access a

single file, which slows down the PC. The greater the fragmentation of files the slower the PC. To

enhance performance, fragments must be rearranged so that files are stored in contiguous clusters.

Such a process is called defragmentation. Many utility programs can be used to defragment the

hard disk. One comes with windows, which is disk defragmenter: start – accessories - system tools

– disk defragmenter.

Partitioning: divide hard disk into separate areas called partitions; each partition functions as if it were a

separate hard disk drive.

g. Formatting: The process of preparing the disk to be used (read/write). It erases the FAT, test the disk

for bad sectors and corrects them, and create new FAT. There are two types of disk format: The high-

level format that most users use and the low-level format. The high-level format does not erase the

data, just the FAT. The low-level format erases all data.

Types of Format:

Low-level format- organizes both sides of each platter into tracks and sectors to define where

items will be stored on the disk.

High-level format defines the file allocation table (FAT) for each partition, which is a table of

information used to locate files on the disk.


Floppy disk organization is shown in figure below:

FAT: (File Allocation Table): is a table of informatio7n about files stored.

Backup 1. Backup is to copy files to a second medium (disk or tape) as precaution in case of a failure (or loss) of

the first medium. Usually backup files are compressed to save space. There are several backup

utilities (software). One comes with windows. To use it go to start – programs – accessories – system

tools – backup. If you can’t find the backup program, then you must install it from the windows CD.

Have the CD ready and go to start – settings – control panel then choose add/remove programs then

windows setup then double click on system tools and choose backup and follow the instructions.

2. Compression utilities: you can find several. A popular one is WinZip.


3. Type of Backup Methods a. Full backup. All files and programs are copied

b. Selective backup. Here a number of file are selected for backup

c. Modified backup. Here only modified files are copied.

Magnetic Tapes (Tape Backup Unit TBU):

Magnetic tape looks like recording cassette. The tapes now are 24GB and 40 GB,… capacities.

They are used only for Backup purposes.

Backup methods:

1. Full backup: copies all files on the HD to the table.

2. Selective backup: copies only user selected files.

3. Modified files backup: copies the modified files only.

Optical Laser Disks

4.72-inch diameter CDs take 650 MB, 700 MB

CD: Compact Disk.

DVD: Digital Versatile Disk or Digital Video Disk.

The CD-ROMs store data in single track that spiral from the center to the outside edge

The speed of the CD drive 24X, 32x, 40x, 48x, 52x are representing the spin speed times the speed of the

original CD standard.

DVDs are double sided and can take up to 18 G Byte.

Optical Laser Devices as shown below:

Optical Laser Technology types:

1. CD-ROM (read only)

2. CR-R (Recordable)

3. CD-RW (Re-writable)

4. WORM (Write Once Read Many)

5. DVD (Digital Video Disk)


Optical Laser Disks

1. History of Compact Disk (CD) recording. It all started in 1980 to record music. First the analog

sound of music is digitized and then it is recorded on a 4.72-inch laser disk that can hold up to 74-

minutes of music called Audio CD. It takes the player 74 minutes to read a full CD. The binary digit is

represented by the presence or absence of pits. A pit is a tiny reflective bump that is burned in by a

laser beam while the land is a flat area separates pits.

2. Computer industry used the technology for data, text, voice… etc.

3. CD organization: on a CD data is represented by a sequence of pits and land in a single spiral track,

which is divided into sectors.

4. A CD-ROM is a Read Only Memory. A CD-ROM has capacity of 650-700MB. The speed at which

the drive reads the CD is measured in X, for example 24X, 32X, or 52X. Here X means the speed at

which the original CD is read (74 minutes means slow speed). 2X means double the speed or 74/2 =

37 minutes to read a full CD. 4X means 74/4 = 18.5 minutes. A 52X speed means the drive reads a full

CD in 1.4 minutes.

5. Multi CD-ROM player/changer. A player that reads several CD-ROMs changing forms one to

another. These players are sometimes called Jukeboxes. The can hold hundreds of CD’s.

6. Digital Video Disk (DVD)

Both DVD and CD technology use laser beams to read microscopic pits in layers. The difference between a

DVD and a CD is that the DVD uses shorter wavelength laser to read more densely packed pits.

The capacity of a DVD is much higher than that of a CD because pits are dense on the surface of

the DVD. Since both the CD and DVD use red laser, the DVD drive can read a CD. The DVD can

have single layer (a coating) or dual layers. Also, the DVD can be single sided or double sided

which means both sides of the DVD are used. In case of dual layers, the top layer is clear

(transparent) and the DVD drive has 2 laser detectors one for the top layer, the other for the bottom

layer. As of summer 2001, the highest capacity of a double sided, dual layer DVD has a capacity

of 17GB. This means it can hold an 8-hours high quality movie.

7. Creating CD-ROMs

a. Mass production. A CD is pressed

b. CD recorder drives: These are affordable recorder. They come in different speeds and can

record once on the medium (the CD). Just 3-4 years ago, a blank CD used to cost 15JD. Now

the cost is less than a dollar. This drive also reads the CD.

c. CD rewriter’s drives. These drives have the ability to read, write, and erase. They need

special medium (CD). The latest with the highest speed as of summer 2001 is from Yamaha. It

reads at speed 40X, writes at speed 20X (writes a full CD in less than 4 minutes) and erase at

speed 10X.

d. CD-Label: Several programs (software) can be used to create CD labels. There are three

labels: The CD label, a circular one, the front cover label, and the back cover label. Usually the

software detects the structure of the files on the CD and creates the contents for the front or

back label. You can try: CDBoxLablerPro, CD-Cover, CDLabler, Cool Label, and CDRLabel.


8. Flash Memory Cards: These are solid state without any moving parts or spinning disks. The size is

about the size of an Identification Card. The highest capacity of flash memory in summer 2001 is

512MB and it sells for less than $600, about $1 per MB. Typical use of flash memory is in digital

cameras, palm computers, cellular phones…etc.

Characteristics of storage media

4- Floppy disk

1. Slow

2. Portable.

3. Low capacity

4. Low cost

5- Hard disk

1. High capacity

2. High speed

3. Fixed

4. More safe.

5. High cost

6- CD

1. Medium to high capacity

2. Medium transfer rate speed

3. Portable

4. Low price

7- Tape

1. High capacity

2. Low speed

3. Sequential reach

4. Portable

5. Low price


Viruses

Virus is a program or piece of code that is loaded onto your computer without your knowledge and runs

against your wishes.

Most viruses can replicate themselves.

All computer virus are manmade.

Types of computer viruses:

There are many types of computer viruses:

Viruses that erase files and programs once they infect the computer.

Viruses that sleep until a given time/date.

Viruses that replicate themselves creating more and more copies of themselves taking the whole

memory and halting the system.

Viruses that infect the FAT, for this type an expert can recover the lost data.

Viruses that runs the hard disk at its highest speed for hours to get overheated and physically damaged.

Viruses that is capable of transmitting themselves over networks.

Viruses that send a copy of themselves to each address in your address book. (email)

Source of Viruses:

Interchangeable magnetic disks

The internet

Local computer networks

Protection:

There are many utilities called Anti Viruses such as kaspersky, Norton 2002 that help you check for infected

files or programs and auto protect your PC from viruses.

An antivirus has a database of all known viruses. Each time you can check a single file or the hard disk for

viruses, the anti-virus checks the file and compare with the definition of viruses in its database. The database

of the definitions of viruses must be updated regularly.

The auto-protects options if enables, checks files when created, open, or saved and it checks the programs

when executed.

Some of the most popular anti viruses are:

a. Norton 2001

b. McAfee

c. PC-Cillin

An antivirus has a database of all known viruses. Each time you scan a single file or the hard disk for

viruses, the anti-virus checks the file and compare with the definition of viruses in its database. When

a virus is found, usually you are asked what to do (clean or delete the infected file or program). The

database of the definitions of viruses must be updated regularly (typically every two weeks). Updates

are available online when you purchase the utility.

The auto-protect options if enables, checks files when created, opened, or saved and it checks the

programs when executed.


Chapter 5

Input and Output Devices

Input devices: Devices that translates data from the out world of the computer into a form that the computer can understand. (Transfer input from human or machines to the computer).

Output devices: Devices that outputs information from the computer into a form that we can understand.

Traditional Input devices:

We mean by traditional, the primary input devices found on all PCs, workstations and each computer system.

Keyboard:

It is the most common device for transferring user input to the computer system.

Two types of keyboard:

a. Alphanumeric keyboards: consists of the alphanumeric keys and other special functions.

b. Special Function keyboards: keyboards that are designed for specific applications. As: ATM.

Point and Drawing Devices:

By the existence of Graphical User Interface (GUI) environments, the pointing devices became the most

important input device for pointing, clicking, dragging drawing,…….etc, which makes the computer usage

easier and faster.

There are many shapes of the pointing devices like:

a- Mouse: in Macintosh computer, the mouse is of one button, but in the pc compatible, the mouse is of

two or even three buttons.

b- Track ball: it is the mouse used in some of the lab tops.

c- Track pad: A small touch-sensitive pad used to move the mouse cursor in some of the lab tops.

d- Track point used also in the lab tops.

e- Digitizer tablet and pen: It is a pen with a sensitive tablet.

f- Joystick: It is a vertical stick with buttons to move the mouse cursor (especially in games).

Other input devices and input processing:

Because of the large of data, new devices are designed for data entry are replacing traditional keyboard.

1. Scanners:

Read and interpret information on a printed matter.

a. Image scanner:

Scan a picture or text into image. Uses laser technology to scan and digitize an image.

The picture is divided into elements or dots called picture elements (Pixels). The quality of the


image is measured in dots per inch (dpi).

dpi is the number of dots per horizontal or vertical inch.

b. Flatbed scanners: scan document and pictures.

c. Stationary label scanner: read special labels on products and process them.

d. Handheld label scanner: these devices read data on a price tags, shipping labels, Book ISBN,…

Optical Character Recognition (OCR):

This is a software that translates scanned text images into text file or word document where you

can edit the text.

Most scanners come with OCR software.

Barcodes:

These codes consist of vertical bars with different thickness representing the numeric.

Scanner can detect the barcode and interpret it.

Image processing:

The picture scanned, you can edit it, save it, send it to others and embed it in a document file slide

show or web page.

2. Smart card:

Small electronic device about the size of a credit card that contains electronic memory.

Used for a variety of purposes:

- Storing digital cash.

- Storing patients medical records.

3. Digital Camera:

Store images digitally rather than recording them in a film.

You can download the picture to the computer. The big advantage of digital camera is making photos

both inexpensive and fast because there is no a film processing,

4. Magnetic stripe: like ATM machines and student cards.

5. Microphones: to enter voice to the computer.

6. Touch screen: used in a special computers.

7. TV cards with video capturing.


Output Devices:

Translate bits and bytes into a form we can understand.

These devices include: screen, printer, …

Categories of output devices:

Softcopy: cannot be physically transferred

Hardcopy: can be displayed out of the machine such as printer.

1. Monitors (Screen) and Graphics Adapter:

The common output device is the monitor (screen) which displays alphanumeric and graphic output.

Monitors are characterized by:

Graphics adapter: the electronic link between the processor and the monitor.

Size: diagonal dimension of the display screen.

Resolution: depends on the number of pixels can be displayed, number of bits used to represent

each pixel.

Pixel is the smallest addressable point on the screen.

Display quality.

Graphic adapter is the electronic device that links the monitor to the processor and mother board.

Graphics adapter can be inserted into an expansion slot on the motherboard. Nowadays, most of the

motherboards have graphics adapter built in.

Most graphics adapters have their own video RAM (VRAM) where they prepare images for display.

VRAM is important because it determine the number of possible colors and resolution of the display.

AGP graphics adapter is better performance by using the PC system RAM directly.

Dot Pitch: is the distance between the centers of the adjacent pixels.

o CGA: colored graphics Adapter.

o EGA: Enhanced graphics Adapter.

o VGA: Visual Graphics Adapter, where screen is divided into 640X480 pixels.

o Super VGA (SVGA) in which screen has 800X600 or 1024X768 pixels.

o XGA: Extended Graphics Array, in which screen has more than SVGA. Example 1600X1200.

Number of colors in VGA was 8 bit (28=256 colors) In SVGA and XGA number of colors reaches

16 bit (65536 colors), 24 bit & 32 bit and last two are called true colors.

Some of the monitors are flat-panel, Most of the flat monitors are LCD (liquid Crystal Display) which is

active or passive matrix of transistors (three for each pixel). Active matrix is better than passive matrix

monitors.

2. Printers:

Printers produce hard copy output.

Printers can be chooses according to the price, size (and weight), speed, quality of out put, color

requirement and even noise level.

1. Dot matrix printers (character printers):

- It is the oldest technology in printers.

- The technology stands on a matrix of pins (8X8, 24X24) that forms a shape wanted to

be printed and hits an ink ribbon.

- It prints one character per hit.

- Low resolution

- Slow.


2. Ink-jet printers (line printers):

- Its resolution is good and equals (in average) 600X600 dpi(dot per inch).

- There are huge ink-jet printers, like “large Format Ink Jet printers” they are used by

Architects, Engineers, Graphics artist, City planners, and others. It can print roll feed

paper up to 4 feet width to 50 feet in length.

- Line printer.

3. Laser printers (page printers):

- High speed.

- High resolution printers.

- It is passed on laser technology.

- Different prices: The shades of gray printers are of popular prices, but colored laser

printers are of high price and their price going down. Popular laser printers are of

1200X1200 dpi, and it, may reach 2000X2000 dpi. Speed of printing reaches 32

pages per minute (ppm).

- Page printer.

Multifunction devices:

Nowadays, there are machines that handle multi functions in paper related tasks like: printing, fax,

scanning, and copying (duplicating), they are called multifunction peripheral Devices.


Chapter Six Computer Networks

Computer network is a group of two or more computer system linked together.

Computers on a network are sometimes called nodes.

Computer networks are used to exchange data using shared resources such as: printers, CD-ROM and files.

Benefits of computer networks

1- Resource sharing.

2- Time saving

3- Communication.

Data Communication Hardware:

Data communication hardware used to transmit digital information between terminals and computers

or between computers and other computers or nodes.

hardware devices are needed as:

1. Network Adapter Card (NIC) or modem.

◦ NIC: enables and controls the exchange of data between the nodes in a LAN.

◦ Modem: modulate demodulate. Digital to analog to digital.

2. Cables for wired connection.

3. Telephone line, satellite, hub or switch.

Data Communication Software:

The software needed by the computers on a network to communicate.

Most Networks are classified as:

Local Area Networks (LANs): located in single buildings or campuses.

Wide Area Networks (WANs): WANs cover a large geographical area, and connect cities and

countries

Local Area Networks (LANs):

Consist of computers, network interface cards, networking media, network traffic control devices, and

peripheral devices.

LANs make it possible for businesses that use computer technology to share, efficiently, such items as

files and printers, and to make possible communications such as email.


LANs are designed to do the following:

Operate within a limited geographic area.

Allow many users to access high-bandwidth media.

Provide full-time connectivity to local services.

Connect physically adjacent devices.

Wide Area Networks (WANs):

WANs interconnected LANs, which provided access to computers of file servers in other location.

Because WANs connected user networks over a large geographical area, they made it possible for

businesses to communicate with each other across great distances.

WAN could communicate with each other to share information and resources, as well as to access the

internet.

Digital bandwidth measurements:

Bandwidth used to describe the LAN and WAN capabilities.

Bandwidth is the measure of how much information can flow from one place to another in a given

amount of time.

“Bits per second” is a unit of bandwidth.

Network Media:

1. Shielded Twisted-Pair cable (STP):

Combines the techniques of shielding, cancellation, and twisting of wires each pair of wires is

wrapped in metallic foil.

Specified for use in Ethernet network installations, STP reduces electrical noise,

STP affords greater protection from all types of external interference, but is more expensive and

difficult to install than UTP.

2. Unshielded Twisted-Pair cable (UTP):

It is a four – pair wire medium – composed of pairs of wires-used in a variety of networks.

Each of the 8 individual copper wires in the UTP cable is covered by insulating material.

UTP cable is more prone to electrical noise and interference than other types of networking media,

and the distance between signal boosts is shorter for UTP than it is for coaxial and fiber optic cables.


3. Coaxial Cable:

Coaxial cable consists of a hollow outer cylindrical conductor that surrounds a single inner wire made

of two conducting elements.

used as a high-frequency transmission line to carry a high-frequency or broadband signal.

The shielding reduces interference from external electromagnetic fields.

Used in TV and video sets and other high frequency application.

Not any more used in Networking as it is replaced by twisted pairs.

4. Optical Fiber:

Fiber optic cable is a networking medium capable of conducting modulated light transmissions.

Clear glass or plastic fiber strands, each approximately the thickness of a human hair.

It is more expensive.

It is not sensitive to electromagnetic interference and is capable of higher data rates than any of the

other types of networking media.

Better than coaxial cable or twisted pair, more secure, used in greater distances.

More secure.


5. Wireless Communication: Wireless signals are electromagnetic waves, which can travel through the vacuum of

outer space and through media such as air.

No physical medium is necessary for wireless signals A common application of wireless data communication is for mobile use. Some examples of mobiles use

includes:

People in cars or airplanes

Satellites

Space shuttles and space stations

Anyone/anything/anywhere/anytime that requires network data

Communications, without having to rely on copper or optical fiber.

Network Topologies:

Topology means the physical shape of the network.

Physical topology should not confuse with logical topology.

Logical topology: is the method used to pass information between computers (nodes).

1. Star Topology:

Each node connected directly to a central hub or switch.

Data passes through the hub (switch) before continuing to its destination.

Advantages:

1. Easy to install.

2. Easy to detect faults and to remove parts.

Disadvantages:

1. Require more cable.

2. If the hub (switch) fails, nodes attached are disabled

3. More expensive than other topologies


2. Bus Topology:

All of its nodes connected directly to one link.

Advantages:

1. Easy to connect nodes to a linear bus.

2. Require less cable length than other topologies.

3. All nodes are connected to each others.

Disadvantages:

1. Entire network shutdown if there is a break in the main cable.

2. Difficult to identify the problem if the entire network shutdown.

Bus topology enables every networking node to see all signals from other devices.

1. This is advantage: if you want all information go to all nodes.

2. This is disadvantage: because traffic problems and collisions are common

3. Ring Topology:

A ring topology is a single closed ring consisting of nodes and links

Each node connected to only two adjacent nodes.

Each node must pass the information to its adjacent nodes.


Chapter Seven

Internet

History of the internet:

The Internet was the result of some visionary thinking by people in the early 1960s who saw great potential

value in allowing computers to share information on research and development in scientific and military

fields. The first proposed a global network of computers in 1962, and moved over to the Defense

Advanced Research Projects Agency (DARPA) in late 1962 to head the work to develop it. Lawrence

Roberts of MIT connected a Massachusetts computer with a California computer in 1965 over dial-up

telephone lines. It showed the feasibility of wide area networking. Roberts moved over to DARPA in 1966

and developed his plan for ARPANET.

The Internet, then known as ARPANET, was brought online in 1969 under a contract let by the renamed

Advanced Research Projects Agency (ARPA) which initially connected four major computers at

universities in the southwestern US (UCLA, Stanford Research Institute, UCSB, and the University of

Utah).

What is the Internet:

- Internet is a world wide collection of interconnected networks.

- Internet has no central computer that controls.

- To avoid conflict between internet addresses an organization founded by the US National

Foundation of science is responsible for regulating the internet like registering unique domain

names.

Intranet: can be LAN or WAN.

Is a private network and is accessible only by its owners.

Example: banks with branches.

Internet connection:

Internet connection can be established via one of the following:

- Connection Information Service Gateway.

- Connect via an Internet Service Provider (ISP):

Dialup connection: using modem and telephone line.

ISP: is a company that provides individuals and organization with access to the internet.

- Network connection:

Via LAN that connected to the internet using one of the following:

1. ISDN (Integrated Service Digital Network). 128 k bps (bit per second)

2. ADSL (Asymmetric Digital Subscriber Line). 9 M bps.

3. T-1 line: 1.544 M bps.

4. T-3 line: 44.736 M bps.


Internet Protocol (IP):

Protocol: set of rules and signals used when computers of the networks communicate.

Example: TCP/IP (Transmission Control Protocol/ Internet Protocol)

TCP/IP Protocol:

- TCP/IP (Transmission Control Protocol/ Internet Protocol).

- TCP/IP is a communication protocol that permits data transmission over the internet.

- The software for this protocol comes with the system as: windows…

- Each message sent divided into packets.

- Packet is a piece of a message transmitted over the network.

- One of the key features of the packet is that it contains the source address, destination address and

the data.

Internet Browser:

- Application software that present you with a Graphical Interactive Interface (GUI) for searching,

viewing and managing information over any network.

- Examples: Internet Explorer and Netscape communicator.

Domain Name:

- each computer on the internet is identified by its unique numeric address which consists of 4

numbers separated by dot with no spaces.

Example: 176.16.1.4 or 206.28.104.10

- the IP of the computer is not easy to remember then alphanumeric addresses are used as

www.aauj.edu or www.yahoo.com

- to translate Internet addresses to their numeric values there is a server called DNS (Domain Name

Server) is used. This is a program (software) that euns on the computer server of LAN.

Domain Types:

- com: commercial

- edu: educational

- gov: government

- org: organization

- net: network.

Access methods:

- HTTP: Hypertext Transport Protocol.

- FTP: File Transfer Protocol:

Protocol used on the internet to transfer files. (send and receive).

It differ from http in that it not open the file to be transferred.

URL: (Uniform Resource Locator)

- consists of the access method (http, ftp) followed by a colon, double slashes, domain name,

domain type and any path to the page domain.

Web server:

- Is a server that host web pages.

- When you design a web page you need to publish it on the internet so other can access it, this can

be done y saving your web page on a web server.

http://www.aauj.edu/

http://www.yahoo.com/


Email address:

- Consists of two parts separated by @.

- Example: user_name@domain_name.domain _type

[email protected]

Telnet:

- A terminal program for TCP/IP network.

- It connects a pc to a server on the internet where the commands are executed as if you are on the

server.

- You need an account (user_name and password) to be able to login to the server.

mailto:[email protected]

Documents

Chapter One Information Technology in Perspectiveto+computers.v7+(1).pdf · Introduction to Computers. By: Rami Hodrob and Ra’fat Amarneh. 1 Introduction to Computers Chapter One