Top Banner
Introduction to ICT & Computer Application OVERVIEW OF ICT What is ICT? Information technology (IT) or information and communications technology (ICT) refers to the use of electronic computers and the telecommunications network to create, store, process, send, and receive information from anywhere, anytime. Components of ICT: are computers, human beings and know-how. What is a Computer? A computer is a machine that is controlled by internally stored programs and that can perform operations without human intervention. It is a collection of hardware and software components. The hardware part consists of one or more processing units, memory units, and input and output devices. It is the equipment you see and the parts you can touch. The software is the set of instructions, called a program that tells the computer what to do, when and how to do it. Computers can be general-purpose or special-purpose: A general-purpose computer can solve any problem that can be expressed as a program and executed within the capacity of the computer, the size of the program, and the speed of program execution. Note that all the discussion in this book is about general-purpose computers. A special-purpose computer is designed to do a specific task. An example is a computer that is capable of doing only word processing. Standalone special purpose computers were popular in the 1930s and early 1940s. Nowadays, they are mostly found embedded within other devices. Many domestic and industrial devices such as mobile telephones and video recorders contain special-purpose computers. Computers embedded inside other devices are commonly referred to as microcontrollers or embedded computers. LIDI Page 1
35
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: ICT Lecture Note

Introduction to ICT & Computer Application

OVERVIEW OF ICT

What is ICT?

Information technology (IT) or information and communications technology (ICT) refers to the use of electronic computers and the telecommunications network to create, store, process, send, and receive information from anywhere, anytime.

Components of ICT: are computers, human beings and know-how.

What is a Computer? A computer is a machine that is controlled by internally stored programs and that can perform operations without human intervention.

It is a collection of hardware and software components. The hardware part consists of one or more processing units, memory units, and input and output devices. It is the equipment you see and the parts you can touch. The software is the set of instructions, called a program that tells the computer what to do, when and how to do it.

Computers can be general-purpose or special-purpose:

A general-purpose computer can solve any problem that can be expressed as a program and executed within the capacity of the computer, the size of the program, and the speed of program execution. Note that all the discussion in this book is about general-purpose computers.

A special-purpose computer is designed to do a specific task. An example is a computer that is capable of doing only word processing. Standalone special purpose computers were popular in the 1930s and early 1940s. Nowadays, they are mostly found embedded within other devices. Many domestic and industrial devices such as mobile telephones and video recorders contain special-purpose computers. Computers embedded inside other devices are commonly referred to as microcontrollers or embedded computers.

Computers have some important characteristics that make them so powerful:

Speed: Computers work at a very high speed. The speed of computers is measured in terms of milliseconds, microseconds, nanoseconds or picoseconds, i.e., one thousandth, one millionth, one billionth, and one trillionth of a second, respectively. They can process information at the speed of a few million instructions per second, called MIPS. As a result, calculations which could take years for a single person could be performed in the order of minutes with computers.

Accuracy: Computers are accurate. However, it must be remembered that they do only what they are instructed to do. If faulty instructions or wrong input are given to the computer, the result will also be wrong.

LIDI Page 1

Page 2: ICT Lecture Note

Introduction to ICT & Computer Application

Consistency: Unlike human beings, computers are highly consistent. They never get tired and are suitable to carryout repetitive and voluminous work.

Storage capacity: Today’s computers can store huge amount of data. Once recorded, a piece of information is never forgotten and any information can be retrieved almost instantaneously.

Parts of a computer

If you use a desktop computer, you might already know that there isn't any single part called the "computer." A computer is really a system of many parts working together. The physical parts, which you can see and touch, are collectively called hardware. (Software, on the other hand, refers to the instructions, or programs, that tell the hardware what to do.)

The following illustration shows the most common hardware in a desktop computer system. Your system might look a little different, but it probably has most of these parts. A laptop computer has similar parts but combines them into a single, notebook-sized package.

Desktop computer system

Let's take a look at each of these parts.

System unit

The system unit is the core of a computer system. Usually it's a rectangular box placed on or underneath your desk. Inside this box are many electronic components that process information. The most important of these components is the central processing unit (CPU), or microprocessor, which acts as the "brain"

LIDI Page 2

Page 3: ICT Lecture Note

Introduction to ICT & Computer Application

of your computer. Another component is random access memory (RAM), which temporarily stores information that the CPU uses while the computer is on. The information stored in RAM is erased when the computer is turned off.

Almost every other part of your computer connects to the system unit using cables. The cables plug into specific ports (openings), typically on the back of the system unit. Hardware that is not part of the system unit is sometimes called a peripheral device or device.

Storage

Your computer has one or more disk drives—devices that store information on a metal or plastic disk. The disk preserves the information even when your computer is turned off.

Hard disk drive

Your computer's hard disk drive stores information on a hard disk—a rigid platter or stack of platters with a magnetic surface. Because hard disks can hold massive amounts of information, they usually serve as your computer's primary means of storage, holding almost all of your programs and files. The hard disk drive is normally located inside the system unit.

LIDI Page 3

Page 4: ICT Lecture Note

Introduction to ICT & Computer Application

CD and DVD drives

Nearly all computers today come equipped with a CD or DVD drive, usually located on the front of the system unit. CD drives use lasers to read (retrieve) data from a CD; many CD drives can also write (record) data onto CDs. If you have a recordable disk drive, you can store copies of your files on blank CDs. You can also use a CD drive to play music CDs on your computer.

CD

DVD drives can do everything that CD drives can, plus read DVDs. If you have a DVD drive, you can watch movies on your computer. Many DVD drives can record data onto blank DVDs.

Tip

If you have a recordable CD or DVD drive, periodically back up (copy) your important files to CDs or DVDs. That way, if your hard disk ever fails, you won't lose your data.

Floppy disk drive

Floppy disk drives store information on floppy disks, also called floppies or diskettes. Compared to CDs and DVDs, floppy disks can store only a small amount of data. They also retrieve information more slowly and are more prone to damage. For these reasons, floppy disk drives are less popular than they used to be, although some computers still include them.

Why are these disks called "floppy" disks? The outside is made of hard plastic, but that's just the sleeve. The disk inside is made of a thin, flexible vinyl material.

Mouse: A mouse is a small device used to point to and select items on your computer screen. Although mice come in many shapes, the typical mouse does look a bit like an actual mouse. It's small, oblong, and connected to the system unit by a long wire that resembles a tail. Some newer mice are wireless.

LIDI Page 4

Page 5: ICT Lecture Note

Introduction to ICT & Computer Application

A mouse usually has two buttons: A primary button (usually the left button) and a secondary button. Many mice also have a wheel between the two buttons, which allows you to scroll smoothly through screens of information.

When you move the mouse with your hand, a pointer on your screen moves in the same direction. (The pointer's appearance might change depending on where it's positioned on your screen.) When you want to select an item, you point to the item and then click (press and release) the primary button. Pointing and clicking with your mouse is the main way to interact with your computer.

Keyboard

A keyboard is used mainly for typing text into your computer. Like the keyboard on a typewriter, it has keys for letters and numbers, but it also has special keys:

The function keys, found on the top row, perform different functions depending on where they are used.

The numeric keypad, located on the right side of most keyboards, allows you to enter numbers quickly.

The navigation keys, such as the arrow keys, allow you to move your position within a document or webpage.

You can also use your keyboard to perform many of the same tasks you can perform with a mouse.

LIDI Page 5

Page 6: ICT Lecture Note

Introduction to ICT & Computer Application

Monitor

A monitor displays information in visual form, using text and graphics. The portion of the monitor that displays the information is called the screen. Like a television screen, a computer screen can show still or moving pictures.

There are two basic types of monitors: CRT (cathode ray tube) monitors and the newer LCD (liquid crystal display) monitors. Both types produce sharp images, but LCD monitors have the advantage of being much thinner and lighter.

Printer

A printer transfers data from a computer onto paper. You don't need a printer to use your computer, but having one allows you to print e-mail, cards, invitations, announcements, and other material. Many people also like being able to print their own photos at home.

The two main types of printers are inkjet printers and laser printers. Inkjet printers are the most popular printers for the home. They can print in black and white or in full color and can produce high-quality photographs when used with special paper. Laser printers are faster and generally better able to handle heavy use.

LIDI Page 6

Page 7: ICT Lecture Note

Introduction to ICT & Computer Application

Speakers

Speakers are used to play sound. They can be built into the system unit or connected with cables. Speakers allow you to listen to music and hear sound effects from your computer.

Modem

To connect your computer to the Internet, you need a modem. A modem is a device that sends and receives computer information over a telephone line or high-speed cable. Modems are sometimes built into the system unit, but higher-speed modems are usually separate components.

Data Processingo Data Processing cycleso Data Processing techniques ( manual, mechanical, electronically )o Data Processing operations (recording, verification, sorting, etc.)

Data processing can be done manually, where brain, paper, and pencil are used. It can be done with the aid of electro-mechanical devices such as a calculator. It can also be done electronically using a computer as a tool. In the rest of this book, data processing is assumed to be done using computers.

Data processing is the process of converting data into information. It involves three steps: input, processing, and output as shown in the following figure.

Input Processing OutputIn general, a computer gets input through an input device such as a mouse or a keyboard, processes it according to the set of instructions given to it, and generates an output.

Input: refers to anything that is given to a computer for processing. It may take various forms such as numbers for calculation, text to be printed, etc.

Processing: The computer has to be told what to do with the input. That means a computer must be programmed with the set of instructions it is required to perform.

Output: refers to the result of data processing such as a printed text. Once the computer processes the input using the instructions given to it, it produces an output using an output device such as a screen or a printer. The output may take different forms. It may be a printout of the results of students, playing music using speakers attached to the computer, etc.

There are three types of processing: batch processing, interactive processing, and real-time processing.

LIDI Page 7

Page 8: ICT Lecture Note

Introduction to ICT & Computer Application

Batch Processing

Batch processing refers to a way of using a computer such that processing is carried out one program at a time without any user intervention. There is no interaction with the user while the programs are being executed. The series of programs (or ‘jobs’) are done one after another. The major benefit of batch processing is controlling the load placed on the computer by careful scheduling. For example, a long batch process could be timed to run overnight. Batch processing is particularly useful for operations that require the computer or input/output devices for an extended period of time. Once a batch job begins, it continues until it is done or until an error occurs. Although the use of batch processing reduced with the move to personal computing and the drop in the price of computers, it is still used a lot by many large businesses for some tasks. An example is the way the Ethiopian Telecommunications Corporation processes bills of customers. The customer does not receive a bill for each separate call but one monthly bill for all of that month’s calls. The bill is created through batch processing, where all of the data are collected and held until the bill is processed as a batch at the end of the month. In many companies, the batch jobs would be scheduled on a timetable, for example 'end of day' and 'end of quarter'.Tip: The original computers worked only in batch processing mode. Each task was at that time called a job. Although the term job is now outdated, it is sometimes used to express the batch processing capabilities of computers.

Interactive Processing

Interactive processing refers to a way of using a computer in which users interact with the computer. The computer accepts input from users, for example, data or commands, and does what the user requests it to do. Input devices such as a mouse and a keyboard are used to interact with the computer. Some examples of interactive processing are word processing and playing computer games. Most data processing activities these days are based on interactive processing.

Real-time Processing

Real-time processing refers to a data processing system where the processing must be carried out within a specified period of time, i.e., the system must quickly respond to the occurrence of certain events.An operation performed after the time limit has no value. This is useful when continuous monitoring is required. Examples are rocket guidance and heat monitoring in a factory. If we take the heat monitoring example, the computer will be programmed to take action when the heat level reaches a certain maximum value.The action could be to start an alarm so that technicians could do something or shut down one or more machines. If an action is not taken immediately, the result will be catastrophic. For example, the factory could be destroyed by fire if the heat level continues to rise.Some real-time systems do not have such a constraint on delay as long as input data can be processed rapidly enough so that no data accumulates. An example is a computerized airline seat reservation system. In such a system, a passenger goes to a ticket office to reserve a seat to a destination on a given travel date. The sales person at the ticket office communicates with a central computer using a computer network to find out if there is a vacant seat. If there is, a seat is reserved for the passenger. In this case, the seat reservation system must respond immediately. Otherwise, you might have two people book the same seat on a flight.

Basics of Computers

Generation of computers

LIDI Page 8

Page 9: ICT Lecture Note

Introduction to ICT & Computer Application

With the above background, recent computer history is usually divided into generations. Depending on the kind of technology they use, computers are classified into four generations. The following are the common improvements that were made from one generation to the next.

enhanced power in terms of the speed at which computers process data, the amount of data they could store, and the range of activities they could accomplish

more convenient to use,

better reliability,

reduced physical size,

less expensive.

First Generation (1945-1955)

Computers in this generation were characterized by the use of vacuum tubes as the main component. As a result, they were very big, filling up entire rooms with tens of thousands of vacuum tubes. However, they were slow, unreliable (with a high failure rate) and expensive. They required extensive air conditioning to dissipate the heat generated by the large number of vacuum tubes. Programming was done by wiring up plug boards to control the machine’s basic functions using sequences of only 0 and 1.

Second Generation (1955-1965)

The transistor was introduced in the mid-1950s and replaced vacuum tubes. As a result, computers ecame smaller in size, faster, and more reliable. These machines could be controlled using high level programming languages such as COBOL (COmmon Business Oriented Language) and FORTRAN (FORmula TRANslator). These programming languages allow the use of Englishlike statements to write programs. Magnetic tapes were also introduced in this generation as storage devices.

Third Generation (1965-1975)

Integrated circuits (ICs) also called chips replaced transistors. In ICs, several transistors are held in a silicon chip, whose size and power requirement is very small. As a result, computers became faster, smaller, and more reliable than before. Magnetic disks took the place of magnetic tapes as storage devices.

Tip: Magnetic tapes are also used today, but only as backup devices because of their cheap price and high storage capacity. Backup means to copy the data from the hard disk into a tape as a precaution. If the disk is damaged, we will not loose the data if a copy is available.

ICs are classified into four groups based on the number of transistors contained in a single chip, called the level of integration: Small-Scale Integration – SSI (contains tens of transistors), Medium-Scale Integration –MSI (contains hundreds of transistors), Large-Scale Integration – LSI (contains tens of thousands of transistors), and Very Large-Scale Integration – VLSI (contains hundreds of thousands of transistors and more).

The first three levels of integration were achieved in the third generation while VLSI is a feature of the fourth generation.

Fourth Generation (1976 - Present)

LIDI Page 9

Page 10: ICT Lecture Note

Introduction to ICT & Computer Application

The development of VLSI technology helped to manufacture computers that are small in size, cheaper in price, more powerful, efficient, and reliable. Microprocessors were developed as a result of VLSI technology.

A microprocessor, also called the Central Processing Unit (CPU), is a tiny device which houses the major components of a computer such as the Arithmetic and Logic Unit (ALU), registers, and the control unit.

Personal computers (PCs) were developed using microprocessors. Because of their low price and user-friendliness, PCs started to be used in homes, smaller offices and schools. Until the mid 1980s, the user could give commands to the computer by typing them using a keyboard, called command-driven interface. Later on commands could be given to the computer by clicking on images displayed on the screen using a mouse, called Graphical User Interface (GUI). This made computers user-friendly. The concept was first developed in 1973 by Xerox Corporation’s Palo Alto Research Centre (PARC) with a prototype called Alto that uses GUI. In 1984, the Macintosh computer from Apple Computer brought the user-friendly interface to many PC users.

Types of computers

Different types of computers are used by different organizations and individuals depending on their finances and their needs. This section discusses the different computer types. In general, computers can be categorized into four types based on their processing power (capability), expected use, cost, and size. These are microcomputers, minicomputers, mainframe computers, and supercomputers.

Microcomputers

Microcomputers (also called personal computers or PCs for short) are the smallest and the cheapest category of computers. Microcomputers come in various forms for a variety of purposes. They can be grouped into three: Desktop, Laptop, and Palmtop computers:

Desktop computer: are the most widely used type of computers by most offices, organizations, and individuals, including in our country. Unlike laptop and palmtop computers, desktop computers have detachable parts.

Laptops: also called notebooks, are smaller versions of microcomputers. They contain most of the input devices (such as a keyboard) and output devices (such as a monitor) and the computer itself, all in a battery-operated package slightly larger than an average book. Despite their size, laptop computers have as high capacity and processing speed as the desktop computers.

Palmtops: are more commonly known as Personal Digital Assistants (PDAs). They are the smallest microcomputers, about the same size of a pocket calculator. These computers usually do not have keyboards but rely on touch screen technology for user input.

Palmtops are typically used for a limited number of functions, such as maintaining a personal calendar, a name and address files, or electronic worksheets. A slightly larger and heavier version of the palmtop is the handheld computer as shown on the left.

Minicomputers

LIDI Page 10

Page 11: ICT Lecture Note

Introduction to ICT & Computer Application

Minicomputers are mid-range computers that are larger and more powerful than microcomputers but are smaller and less powerful than mainframe computers. Minicomputers cost less to buy and maintain than mainframe computers. Minicomputers are used for a large number of business and scientific applications. They are popular in scientific laboratories, research centers, universities and colleges, engineering firms, industrial process monitoring and control, etc. The term minicomputer is largely obsolete these days.

More modern terms for such machines include midrange systems, workstations, and servers.

Mainframes

In the early days of computing, mainframes were huge computers that could fill an entire room or even a whole floor. The term “mainframe” originated during the early 1970s with the introduction of smaller, less complex computers which became known as minicomputers. The industry and users then coined the term "mainframe" to describe larger, earlier types (previously known simply as "computers").

Mainframes were expensive in price and were mainly owned by government institutions and large companies. They were used for large operations such as industry/consumer statistics, and bank transaction processing. As the size of computers has fallen while the power has increased, the term mainframe has fallen out of use. The term that is mostly used nowadays is enterprise server instead of mainframe. However, you will still hear the term being used by some, particularly in large companies to describe the huge machines processing millions of transactions every day.

Supercomputers

The term supercomputer has been coined to describe a category of extremely powerful computers designed for high-speed processing. A supercomputer is generally characterized as being the fastest, most powerful, and most expensive computer. Although some supercomputers are single computer systems, most are comprised of multiple high performance computers working together as a single system. Uses of such computers include research organizations, military defense systems, national weather forecasting agencies, large corporations, aircraft manufacturers, etc.

Exercise

I. Write True or False

______1. Most of the computers nowadays are special-purpose.______2. A Computer takes information as input and generates data as output.______3. Computers get faster and powerful from one generation to the next.______4. LSI refers to integrating hundreds of thousands of transistors and more in a square centimeter of silicon.______5. A computer is said to be a supercomputer in relative terms, i.e., the one that is the most powerful in its time.______6. In elections, the voting process cannot be conducted using computers.______7. Computers can be used to find out to which person a fingerprint belongs.

II. Choose the correct answer(s)

LIDI Page 11

Page 12: ICT Lecture Note

Introduction to ICT & Computer Application

1. Which one or more of the following may not involve interaction of a computer with the user in data processing?

a. Batch processingb. Interactive processingc. Real-time processing

2. One of the following is not a benefit of computer networks.a. Sharing resources b. Exchanging informationc. Duplicating documents d. Connecting branch offices

3. Microprocessors were developed as a result of which technology.a. LSI b. VLSIc. MSI d. SSI

4. One of the following is not a name used instead of the outdated term “minicomputer”.a. Enterprise server b. Serverc. Midrange system d. Workstation

5. In the health sector, for which tasks can computers be used?a. Disease diagnosis b. Managing drugs and other materialsc. Patient appointment d. All of the above

6. One of the following is not a benefit of teleworking.a. Reduced office space requirement b. Solution to traffic congestionc. Access to employment information d. Increases employability of some groups

III. Fill in the blank spaces.

1. A computer is a collection of ____________________ and _______________components.2. The three steps of data processing are ____________________,________________________, and ______________________.3. The three methods of data processing are ____________________,________________________, and ______________________.4. Computers can be categorized into the following four based on their processing power, expected use, cost, and size: ____________________,__________________, ____________________, and ___________________.5. A slightly larger and heavier version of a palmtop computer is called a ____________________ computer.

IV. Answer the following questions.

1. State and describe three of the characteristics that make computers so powerful.

2. What are the uses of a computer in the home?

LIDI Page 12

Page 13: ICT Lecture Note

Introduction to ICT & Computer Application

Peripheral Devices

A peripheral device is any computer hardware that is plugged into the computer, i.e. not the motherboard, the CPU, main memory, power supply or the expansion cards. We can split peripheral devices into three categories - input, output and storage. In the following sections, some of the most common peripheral devices will be discussed.

Input Devices

Input devices are the part of the computer hardware through which the computer gets data and instructions from the outside world. Keyboard, light pen, graphics tablet, barcode reader, mouse, scanner, digital camera, and microphone are some examples of input devices.

Keyboard

Keyboard is the most common input device. It is similar to a typewriter and is used to enter information and instructions into the computer. In addition to letter keys, most keyboards have number pads, function keys and other special purpose keys that make the computer easier to use.

Mouse

A mouse is a small device with buttons on the top (see the left figure below) and a ball on the bottom (see the right figure below). As you move the mouse across a surface (such as a mouse pad), a pointer on the screen moves in a way which corresponds to the direction and speed the mouse was moved. There is also an optical mouse that tracks the motion of the mouse by reflecting light off of a special mouse pad.

One major innovation in mouse buttons is the scroll wheel: a small wheel, which can be rotated as shown on the right. Usually, this input is translated into "scrolling" up or down within the currently selected window. This is especially helpful in navigating a long document.

LIDI Page 13

Page 14: ICT Lecture Note

Introduction to ICT & Computer Application

Tip: There are also other pointing devices such as a trackball, touchpad, pointing stick, light pen, joystick, head pointer, eye tracking devices, various kinds of digitizing tablets which use a stylus, and even a special "data glove" that translates the user's movements to computer gestures.

Scanner

A scanner is a device that converts visual information into digital data. Its most common use is to put pictures into a computer so they can be used for different documents. There are many types of scanners, the most common ones being flatbed and sheetfed scanners:

Flatbed Scanners: The most common desktop scanners resemble photocopy machines, in that the item being scanned rests on a glass plate while the scanning head moves underneath it. These flatbed scanners are versatile because they can scan flat originals of various sizes, and they can even scan small three-dimensional objects.

Sheetfed Scanners: These scanners are more like a fax machine than a photocopier, because they move the page being scanned past the scanning head, rather than the other way around. Some sheetfed scanners come with built-in document feeders that can scan multiple-page documents unattended.

Digital Camera

A digital camera is a camera that does not use film, but instead stores the photographs in the memory of the camera. These images can then be downloaded to a computer. Some digital cameras can also store images in plug-in cards, or on disks. There are different types of digital cameras. The following are some of the types of digital camera:

Video cameras: used to capture full motion video. Still cameras: used to capture still (motionless) images.

Webcams: are digital cameras attached to computers, used for video conferencing or other purposes. Webcams can capture full-motion video as well, and some models include microphones or zoom ability.

Output Devices

Output Devices are parts of the computer that are designed to receive output from the computer and provide it to the user. Examples of output devices are monitors, speakers, and printers.

Monitor

A monitor is an output device similar to a television screen that receives video signals from the computer and displays the information for the user. It is the most commonly used output device for

LIDI Page 14

Page 15: ICT Lecture Note

Introduction to ICT & Computer Application

displaying text and graphics from a computer. Today's monitors have much better quality displays than any TV. There are two main types of monitors:

CRTs (Cathode Ray Tubes): have a large part at the back and are most common on desktop computers.

LCDs (Liquid Crystal Displays): are flat screens and are commonly used on laptops and some desktop systems.

Monitors differ in several ways. However, the major differences are the resolution and the number of colors it can produce at those resolutions.

Resolution refers to how clear the image on the monitor is. It is a width times height measurement of computer monitor display capabilities in pixels. Pixels are individual dots that are used to display an image on a computer monitor. The more pixels a screen can show, the higher the quality.

Tip: A monitor is commonly called a screen. You can use either term.

A monitor that displays information only in black and white is called a monochrome monitor while the one capable of displaying color is called a color monitor.

Printer

A printer is a device that produces a paper copy, sometimes called a hard copy, of data stored in a computer.//*- Broadly speaking, there are two types of printers: impact printers and non-impact printers.

Tip: Hard copy refers to information printed on paper while soft copy means information stored on a secondary storage device.

Speaker

A speaker is an output device that allows you to hear voice, music, and other sounds from your computer. There are usually two of them and they come in various sizes.

Secondary Storage Devices

The term storage or secondary storage refers to the parts of a computer that retain data permanently, even after turning off the computer. Examples of storage devices would be floppy disk, hard disk, Compact Disk (CD), Digital Versatile Disk (DVD), and magnetic tape. Commonly used secondary storage devices can be grouped as magnetic or optical. Magnetic devices use magnetic technology to write and read data from the storage surface. This category includes hard disk, floppy disk, and magnetic tape. On the other hand, optical storage devices use laser technology. CD and DVD fall under this second category.

LIDI Page 15

Page 16: ICT Lecture Note

Introduction to ICT & Computer Application

Magnetic Storage Devices

Floppy Disk------------------------------------------------

A storage medium that is made from a disk of flexible plastic (the "floppy" part) covered with a magnetic material. The floppy disk is many decades old. The standard floppy disk can hold 1.44MB of data and has 3.5 inch diameter. Floppy disks are slow, unreliable and can hold much less data than the other storage devices. A floppy disk refers to the disk itself and a floppy drive refers to the slot that is used to read and write data onto the floppy disk.

Hard Disk

A hard disk contains both the disk and the drive (the slot) that is used to read and write data on the disk. A hard disk uses rigid turning disks to store data and programs. They have read/write heads which can read data from the hard disk and write data to the hard disk. The hard disk drive is sealed. This protects the hard disk drive internals from dust, condensation, and other sources of contamination. Hard disks can store much more data than floppy disks, and access and transmit it faster.

Currently an average hard disk can store 60 to 80 GB of data.

For both hard disks and floppy disks, data is stored on the surface in sectors and tracks. As shown in the figure, tracks are concentric circles, and sectors are pie-shaped sections on a track.

Magnetic Tape

A tape drive, also known as a streamer, is a device that reads data from and writes data to a magnetic tape. It is typically used for archiving or backing up of data stored on hard disks. Magnetic tapes are long lasting and inexpensive storage media.

Optical Storage Devices

LIDI Page 16

Page 17: ICT Lecture Note

Introduction to ICT & Computer Application

Optical storage is a newer storage technology using a high-power laser beam to burn small holes in a disk's surface coating. Data is represented by the presence and absence of holes in the disk’s surface.

Optical media are more durable than tape and less vulnerable to environmental conditions. On the other hand, they tend to be slower than typical hard disks, and hold less data.

Compact Disk (CD)

A compact disc (CD) is an optical disk used to store digital data. It was originally developed for storing digital audio

Types of CDs

The different types of CDs include: CD-ROM, CD-R, and CD-RW:

CD-ROM (Compact Disc – Read Only Memory): is a version of the CD that allows the information to be stored so that the user can only read from the disks. Once data is recorded on a CD-ROM, new data cannot be stored and the disc cannot be erased. Although CD-ROMs look like music discs, they can only be used with a computer equipped with a CD-ROM drive.

CD-R (Compact Disc - Recordable): refers to compact disks that can be recorded only once, but read many times. If the recorded content is no longer wanted, additional material can be recorded only on the remaining space on the disk. The disks themselves are constructed differently from ordinary CDs.

CD-RW (Compact Disc - Rewritable): is an extension of CD-R whereby you can rewrite data or audio to the same CD many times. Not all CD drives can read CD-RWs.

Digital Versatile Disc (DVD)

DVD is an optical disc storage media that can be used for storing data, including movies with high video and sound quality. DVDs resemble CD: their physical dimensions are the same – 12 cm or the mini 8cm - but they are encoded in a different format. This enables DVDs to store more data than that of CDs. A typical DVD can often hold more data than 6 CDs. DVDs can store an entire movie, or several hours of audio.

Common Types of DVDs

DVD-ROM: These DVDs are read-only disks. They are accessed using a special DVD drive attached to a personal computer. They are often used for movies (which are more specifically referred to as DVD-Video) and computer games.

DVD-R: It offers a write-once, read-many times storage format similar to CD-R, but can hold more information than a CD-R.

DVD-RW: A recordable DVD format similar to CD-RW.

LIDI Page 17

Page 18: ICT Lecture Note

Introduction to ICT & Computer Application

Applications and Systems Software

Software is a term for computer programs. A program is a set of instructions that enables a computer to operate or instructions that tell the computer how to perform a specific task.

Programming Languages

Programs are written by computer programmers using a programming language. There are three categories of programming languages: machine language, assembly language, and high level programming language.

Machine Language

A computer has a defined set of basic instructions. Machine instructions inside the computer are represented by 0s and 1s, called binary digits. The programming language that uses such binary instructions is called machine language. For example, to tell the computer to add the numbers 3 and 4, we may write: 00001111 00000011 00000100.

Assembly Language

Writing programs using machine language is very difficult since it is difficult to read and find errors using 0s and 1s. Assembly languages use symbolic codes, called mnemonics, to write programs. Instead of a sequence of 0s and 1s, they use words such as MUL, ADD, etc. Such programs must be converted to machine code to be understood by the computer. A program that converts assembly languages into machine code is called an assembler. For example, to tell the computer to add the numbers 3 and 4, we may write: ADD 3, 4.

High Level Programming Language

High Level Programming Languages use English like statements to write programs. For example, to tell the computer to add the numbers 3 and 4, we may write: x = 3+4. Such programs must be converted to machine code to be understood by the computer. A program that converts high level language programs into machine code is called a compiler. There are a number of high level programming languages, each designed to suit some applications. A few examples are BASIC, FORTRAN and Java. "A program written in assembly language or high level programming language is called a source program (or source code). The one that is converted to machine code (by an assembler or a compiler) is called an object program (or object code). Software is divided into two major classes: systems software and applications software.

Applications Software

LIDI Page 18

Page 19: ICT Lecture Note

Introduction to ICT & Computer Application

Applications software allows a user to accomplish one or more specific tasks. Typical applications software include office suites, business software, educational software, databases and computer games. Following are examples of application software:

Word processing: WordPerfect, OpenOffice, AmiPro, and MS-Word. Desktop Publishing: MS-Publisher, QuarkXPress, and Adobe InDesign.

Spreadsheet: Lotus 1-2-3, MS-Excel, and Corel Quattro Pro.

Database management: MS-Access, MySQL, and Oracle.

Presentation: MS-PowerPoint, Freelance Graphics, and Adobe Persuasion.

Bespoke and Off-The-Shelf Software

Whatever type of software system you are considering for your business, you will need to decide whether to develop it from scratch or to buy the software off-the-shelf. MS-Office, which contains MS-Word, MS-Excel, MS-Access, MS-PowerPoint, and MS-Publisher, can be taken as an example of off-the-shelf software.

Tip: MS stands for Microsoft and is used as a prefix to products developed by the Microsoft Corporation. You can also leave out the prefix and use names such as Excel, Word, etc.

Generally speaking, off-the-shelf software have features that most people would want and, for more complex applications, you may be able to customize them. Bespoke systems are tailored exactly to the requirements of the customer in question. In addition, the software can evolve in step with your requirements providing an ongoing perfect fit. However, this benefit has to be weighed against the cost, which can be much higher than off-the-shelf software.

Systems Software

Systems software includes the computer's basic operating system. The term also usually covers any software used to manage the computer and the network. Thus we can say that systems

LIDI Page 19

Page 20: ICT Lecture Note

Introduction to ICT & Computer Application

LIDI Page 20

Page 21: ICT Lecture Note

Introduction to ICT & Computer Application

operating systems, device drivers, programming tools, utilities and more.

Operating Systems

An operating system is the most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks,

LIDI Page 21

Page 22: ICT Lecture Note

Introduction to ICT & Computer Application

such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.

For large systems, the operating system has even greater responsibilities and powers. It is like a traffic policeman - it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.

As of 2005, the major operating systems in widespread use have consolidated into two main families: the Unix-like family and the Microsoft Windows family.

The Unix-like family is commonly used to refer to many operating systems, which resemble an operating system called Unix.

The Microsoft Windows family contains operating systems such as Windows 9x, Windows 2000, and Windows XP.

Operating systems provide a software platform on top of which other application programs can run. The application programs must be written to r

un on top of a particular operating system. Your choice of an operating system, therefore, determines the applications you can use.

Units of Data Measurement and Representation

This section discusses how data is represented in the computer system. It also deals with measuring units of the size of memory and storage devices.

The Binary Number System

LIDI Page 22

Page 23: ICT Lecture Note

Introduction to ICT & Computer Application

Digital computers store data using two state components. With two such states, we can represent exactly two different values. These two values correspond to the two digits used by the binary number system. As such, the computer employs the binary number system.

The binary number system works just like the decimal number system, with two exceptions: the binary number system allows only the values 0 and 1 (rather than 0-9), and the binary number system uses powers of two rather than powers of ten.

Bits, Bytes, KB, MB

A bit (short for binary digit) is the smallest unit of data; it represents one binary digit (0 or 1). However, computers usually do not operate on single bits, rather they store and manipulate a fixed number of bits. Most often, the smallest unit or number of bits a computer works with is eight bits. These eight bits make up a byte.

A byte is a group of eight bits that usually make up a single character - letter, number, or special character.

Most coding standards use eight bits, and the eight bits represent a single character, such as the letter “A” or the number “7”. Thus, the computer can store and manipulate an individual byte (a single character) or a group of bytes (several characters, a word) at a time. These individual bytes, or groups of bytes, form the basic unit of memory. The memory size can be measured in Kilobytes (KB), Megabytes (MB), Gigabytes (GB), etc. The common units are shown in the following table:

Unit Equivalent Quantity

1 Byte 8 bits = 1 character 1 Kilobyte (KB) 210 = 1,024 bytes

1 Megabyte (MB) 220 = 1,048,576 bytes

1 Gigabyte (GB) 230 = 1,073,741,824 bytes

1 Terabyte (TB) 240 = 1,099,511,627,776 bytes

Tip: A group of related bytes in memory that are treated as a single addressable unit or entity make up a word. " Storage space (disks, CDs, memory, etc.) is measured using the above units.

Data Representation

Data representation refers to the methods used to represent information stored in a computer. Computers store many different types of information such as numbers, text, graphics of several varieties (still image, video, animation), and sound. All types of information are stored in a computer in the same simple format: 0's and 1's. How can 0's and 1's represent things as diverse as your photograph, your

LIDI Page 23

Page 24: ICT Lecture Note

Introduction to ICT & Computer Application

favorite song, a recent movie, and your letter? It all depends on how we interpret the information. Computers use numeric codes to represent all the information they store. The codes used by computers are based on the binary number system instead of the more familiar decimal number system.

Computers use a variety of different codes. Some are used for numbers, others for text, and still others for sound and graphics.

Text Representation

Text can be represented easily by assigning a unique number for each symbol used in the text. For example, the widely used ASCII code (American Standard Code for Information Interchange) has 128 different symbols (all the characters found on a standard keyboard, plus a few extra), and gives each a unique numeric code between 0 and 127. In ASCII, an "A" is 65 (which is equivalent to 1000001 in binary)," B" is 66, "a" is 97, "b" is 98, and so forth. There are also other standards such as BCD, EBCDIC, and UNICODE that represent characters differently.

Graphics Representation

Graphics that are displayed on a computer screen consist of pixels: the tiny "dots" of color that collectively "paint" a graphic image on a computer screen. The pixels are organized into many rows on the screen. In one common configuration, each row is 640 pixels long, and there are 480 such rows. Another configuration can be 800 pixels per row with 600 rows, which is referred to as a "resolution of 800x600."

both pixel has two properties: its location on the screen and its color. A pixel's color is represented by a binary code, and consists of a certain number of bits. In a monochrome (black and white) image, only 1 bit is needed per pixel: 0 for black, 1 for white, for example. A color image would need more bits. For example if you used 2 bits for each color, there would be 4 different possibilities: 00,01,10 and 11 and each could be given a color.

Exercise

1. Write true or false.

1. ______CD is a magnetic storage media. 2. ______A floppy disk stores data in sectors and tracks.

3. ______CD-ROM is a writable storage media.

4. ______The physical dimensions of a DVD are greater than that of a CD.

5. ______To each surface of a hard disk, there is a separate read/write head.

6. ______In a hard drive, it is the read/write head that rotates 360 degree at a constant speed.

LIDI Page 24

Page 25: ICT Lecture Note

Introduction to ICT & Computer Application

II. Answer the following questions

7. Put the following storage media in an increasing storage capacity: CD, DVD and Floppy Disk 8. Why is the hard disk sealed?

9. What was the original purpose of optical storage devices?

10. Discuss the difference between CD-R and CD-ROM.

11. Why do DVDs have more data storage capacity than CDs?

12. What are the main purposes of using a floppy disk?

13. Discuss the difference between disk and disk drive?

14. What is the reason for the usage of the binary number system when data is represented in a computer system?

15. Suppose your computer’s hard disk capacity is 20GB. What will be this capacity in

a. Megabytes (MB) _____________________?

b. Kilobytes (KB) ______________________?

c. Bits _______________________________?

16. When using ASCII code, the number of bits that are used to represent a character is ___________.

17. How do you represent graphics in the computer system?

18. A 64 color image requires __________ bits per pixel.

When ASCII code is used, the corresponding binary value for the letter “A” will be 01000001 which is equivalent to the decimal number 65. In the same way “B” is represented as 01000010. How can you represent the text “ABEBE” using ASCII code? The answer is as started below and try to finish it: 10000011000010 … Hint: First try to get the ASCII code for the letter “E”.

Review Questions

I. Write True or False

1. ______The computer software is the physical component of the computer system. 2. ______The processor is the largest circuit board in the computer system.

3. ______Control unit is part of the processor.

LIDI Page 25

Page 26: ICT Lecture Note

Introduction to ICT & Computer Application

4. ______Memory unit is responsible for the execution of instructions.

5. ______Computer peripherals can be categorized as input units, output units and storage units.

6. ______Webcams are digital cameras that are often used for video conferencing.

7. ______The usage of LCDs by desktop computers is common.

8. ______A monitor with 600X800 resolution has better display quality than the one with 250X400.

9. ______Multimedia speakers have a built-in amplifier.

10. ______Floppy disks are more reliable than hard disks. II. Choose the correct answer(s)

11. Which of the following will not be in the chassis of the computer? a. Processor b. Hard disk c. Power supply unit d. Monitor

12. Which of the following is not true regarding RAM?

a. Volatile

b. Has less size than hard disk c. Also called memory d. Stores data permanently

13. One of the following is not an input device.

a. Light pen b. Mouse c. Speaker d. Microphone

14. Which of the following uses tracks and sectors to store data

a. Floppy disk b. Hard disk c. Compact Disk d. a and b

15. Which of the following storage units store data by forming pits on the surface of the media?

a. Floppy disk b. Hard disk c. Compact Disk d. a and b

LIDI Page 26