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Preface In this, the third edition of Oxford Information Technology for CSEC, we are providing new material that incorporates the recent changes to the Caribbean Examination Council’s Information Technology (IT) syllabus. Almost 20 years into the new millennium, it is clear how information and communications technology is an invaluable resource in every sector, including education.is textbook aims to support the interest of the Caribbean student in the use of ICT tools for productivity and problem solving.It will provide you with the support material to fully explore every section of the IT syllabus.e resources in the textbook are presented through topic discussion, worked examples and a wide range of questions. Our years of interacting with students and educators from across the region have helped us to design this resource material to be used eectively. For the most part, the chapters have been aligned with the sections of the syllabus. However, we have maintained the separation of Chapter 1 (Fundamentals of hardware and software) and Chapter 2 (Information processing) to provide detailed treatment of these sections for the coverage of syllabus Section 1 (Computer Fundamentals and Information Processing). Among the practical chapters is the updated Chapter 6 (Web page design), which provides material needed for the theory examination and the practical requirement for the School Based Assessment (SBA). Chapter 9 (Problem solving) and Chapter 10 (Program implementation) have continued to prove challenging to Caribbean candidates. Teachers can now choose which programming language their students can use, while the textbook continues to oer support in these areas of programming, with several examples and questions. Chapter 11 introduces Pascal programming fundamentals for those comfortable with this method of writing code, while Chapter 12 introduces Visual Basic for Applications, which can support the Microsoft applications used for word processing, spreadsheets and database management. Each chapter is subdivided into sections based on the specic objectives from the syllabus. End-of-section questions provide reinforcement on the topics covered in a section.ere are more questions at the end of each chapter which take a dierent approach; testing learning from other chapters.e intention is to familiarise students and teachers with this approach to questioning for the new exam format, using realworld examples.e appendix includes useful hints for guidance through the SBA, whether candidates are working as individuals or as a part of a group. It is our intention through this text to once again provide a supportive resource for each candidate to achieve success in their IT examination, as each candidate prepares to embrace new technologies which will inevitably arrive in years to come. CSEC IT Structure Syllabus Section Paper 1: 1 ¼ hours: 60 compulsory multiple-choice questions. 30% of final mark 35 questions – Theory 15 questions – Productivity tools 10 questions – Problem solving Paper 2: 2 hours: Four compulsory questions from all areas of the syllabus. 45% of final mark 35 marks – Theory 30 marks – Productivity tools 25 marks – Problem solving and programming Paper 3-1: School Based Assessment (SBA). One practical assignment comprising word processing, web page design, spreadsheets, database management, problem solving and programming. 25% of final mark Productivity tools Problem solving and programming Paper 3-2: Alternative to the School Based Assessment for private candidates. A theory and practical paper testing the skills required for the School Based Assessment. 25% of final mark Productivity tools Problem solving and programming
1 Fundamentals of hardware and software 1.1 Basic computer components 6 1.2 Input devices and media 8 1.3 Output devices 15 1.4 Primary memory 19 1.5 Secondary storage 21 1.6 System software 26 1.7 Data processing 27 1.8 Application software 29 1.9 User interfaces 31 1.10 Types of computer systems 34 1.11 Common computer hardware problems 36 End of chapter exam-style questions 38 2 Information processing 2.1 Data and information 40 2.2 Validation and verication 42 2.3 Automated methods of data capture 46 2.4 File organisation and access 49 2.5 Information processing 54 End of chapter exam-style questions 60 3 Computer networks and web technologies 3.1 Computer networks 62 3.2 Web technologies 70 End of chapter exam-style questions 77 4 Implications of misuse and cyber security 4.1 Computer vulnerability 79 4.2 Misuse of information 81 4.3 Data protection 84 4.4 Impact of IT in the workplace 89 4.5 Personnel in computer-related elds 94 4.6 Implications of ICT 95 End of chapter exam-style questions 101 5 Word processing 5.1 Introduction to word processing 103 5.2 Document organisation 110 5.3 Tables and columns 112 5.4 Reviewing your work 116 5.5 Combining les and importing data 120 5.6 Table of contents 122 5.7 Mail merge 124 5.8 Printing the document 129 5.9 Fillable electronic forms 130 End of chapter exam-style questions 136 6 Web page design 6.1 Introduction to web page design 138 6.2 Designing a web page 141 6.3 Creating a web page 147 End of chapter exam-style questions 150 7 Spreadsheets 7.1 Introduction to spreadsheets 152 7.2 Common spreadsheet features 154 7.3 Developing a simple spreadsheet 160 7.4 Formatting a spreadsheet 170 7.5 Searching for records 172 7.6 Charts 180 7.7 Printing a spreadsheet 185 7.8 Importing les and linking data 186 End of chapter exam-style questions 188 8 Databases 8.1 Introduction to database management 191 8.2 Common database management features 193 8.3 Joining multiple database tables 200 8.4 Capturing and entering data 203 8.5 Searching and sorting 209 8.6 Calculated elds 217 8.7 Report formats 220 8.8 Importing and linking data 225 8.9 Developing database applications 227 End of chapter exam-style questions 228 9 Problem solving and program design 9.1 Introduction to problem solving 231 9.2 Algorithm design 233 Contents
9.3 Pseudocode 235 9.4 Flowcharts 246 9.5 Arithmetic,relational and logical operators 252 9.6 Testing algorithms 256 End of chapter exam-style questions 258 10 Program implementation 10.1 Programming languages 260 10.2 Writing a program 262 10.3 Running a program 266 10.4 Testing and debugging techniques 268 10.5 Program documentation 270 End of chapter exam-style questions 272 11 Programming with Pascal 11.1 Introduction to Pascal 274 11.2 Structure of a Pascal program 277 11.3 Formatting the output of Pascal programs 280 12 Programming with Visual Basic for Applications 12.1 Introduction to Visual Basic for Applications 283 12.2 Writing in VBA 287 Appendix 1 Information Technology School-Based Assessment guidelines 292 2 Teacher guidelines for the School-Based Assessment 295 3 Guidelines for problem solving and program design 296 Answers to end of topic questions 298 Index 305 What's on the website? ♦ Answers to all End of Chapter Exam-style Questions in this book. ♦ Additional Exam-style Questions for each chapter with sample answers and examiner analysis. ♦ Interactive Paper 1 multiple choice test, Practice Paper 2, worked SBA Paper 3 with advice on online marking, SBA alternative Paper 3 ♦ Answers to all Workbook questions ♦ Comprehensive glossary of terms used in this book. www.oxfordsecondary.com/9780198437161
CHAPTE 1 FUNDAMENTALS OF HARDWARE AND SOFTWARE 6 1.1 Basic computer components Computers are an important aspect of information technology. A computer is an electronic device, operating under the control of instructions stored in its memory.Whether on its own or connected via a network (such as the Internet), it can: ◆ accept data (input) ◆ manipulate data (processing) ◆ produce results (output) from the processing ◆ store the data and results for future use (storage). ese four basic tasks of any computer represent the IPOS cycle (Fig 1.1). Data is input to the computer Data is processed into information Information is output to the user in various forms Data or information is stored for a short or long time Fig 1.1 Four basic tasks of the IPOS Cycle Components of a computer e term ‘computer’ generally refers to desktop machines and laptops but it can also include handheld games consoles as well as portable devices, such as smartphones and tablets. e basic components of a computer are categorised as either hardware or software. Hardware is is the name given to the physical parts of a computer (Fig 1.2).ere are ve general categories: 1 e central processing unit (CPU) is the brain of a computer and controls how the rest of the computer works.It includes the control unit (CU) and the arithmetic and logic unit (ALU).e CU carries out instructions in the software and directs the ow of data through the computer.e ALU performs the calculations and logic operations. 2 Input devices get data into a computer. A mouse, a keyboard and a scanner are all input devices. 3 Output devices get processed information out of a computer, for example to a printer, computer screen or even to speakers. 4 Memory enables a computer to temporarily store instructions and data. 5 Storage media include hard disks, CD-ROMs, DVDs, and USB ash memory sticks, while the storage devices include hard disk drives, CD-ROM drives and DVD drives. Most of these devices can read data whilst others, such as USB ash memory sticks, allow data to be saved as well as read. Peripheral devices are located outside the CPU but are controlled by it.at is, they can be added to a computer system.Input, output and storage devices may be peripheral devices. Software is is the name given to computer programs that tell the hardware how to work.Without software the computer hardware would do absolutely nothing, as
1.1 Basic computer components 7 there would be no instructions. Software includes the following types of program. Computer programs ese are instructions (programs) produced by programmers to create system and application software. System software is software is usually called an operating system since it controls the hardware and how all other software works.e most commonly used operating system is Windows,written by the Microsoft Corporation. System software also includes utility software.is software aims to protect and maintain the system software, just as a mechanic maintains the smooth working of a car’s engine when it is serviced.Examples of the tasks undertaken by utility software include: protecting software against damage caused by computer viruses,making copies of les (‘backing up’), and recovering les after software has stopped working (‘crashed’). Application software Application software is software that instructs a computer to carry out a specic task.Word processors, spreadsheets and databases are all application software. Questions 1 List the four basic tasks of any computer. 2 State the name of the cycle that represents the four basic tasks listed in question 1. 3 What is the general name given to the physical parts of a computer? 4 Explain what each of the following terms represent: a CPU b CU c ALU. 5 Explain the dierence between an input device and an output device. 6 What is another name for system software? 7 What is the general name given to each of the following descriptions: a computer programs that tell the hardware how to work b telecommunications equipment through which data and information can be accessed. Information and communication technology Now that we have discussed how data can be input, processed, stored and output to produce information, we introduce two important terms: Information Technology (IT) is the term used to describe the equipment (hardware and computer programs or software) that allows us to access, retrieve convert, store, organise, manipulate and present data and information.IT may also refer to the use of such equipment and programs to produce the information. Communications Technology (CT) is the term used to describe telecommunications equipment through which data and information can be accessed. Examples of CT equipment are phones, faxes, scanners, modems and computers. Output device (printer) Input devices (keyboard & mouse) Output device (monitor) System unit case containing the central processing unit (CPU) Storage device (CD-ROM) Fig 1.2 The basic categories of computer hardware
8 1.2 Input devices and media Data must be provided in a suitable form for any computer system to be able to process it. So, it is always important to think of the dierent ways of entering data into a computer, particularly since all data needs to be entered as accurately as possible. ‘Input’ means to enter data, programs, commands and user responses into the memory of a computer. erefore, an input device is any device that transfers data from the outside world into a computer. Although most input devices can be connected to desktop computers, you probably come across others and do not realise it! For example, every time you use a remote control for a television or a games console, data is entered using a special keyboard. ere are many dierent input devices and media, each one being suitable for a dierent purpose.e two general categories of input devices are manual input devices and direct data entry (DDE) devices. Manual input devices With a manual input device, you must enter or transfer data into the computer yourself. Some examples of these devices are explained next. Keyboard and keypad A keyboard has a set of alphabet keys, a set of digit keys and various function keys, so the data entered by the person operating the keyboard is in the form of individual letters, words or numbers.When you press a key on the keyboard, a number (code) is sent to the computer to tell it which key you have pressed.e keyboard has the disadvantage that it is easy to make mistakes by pressing the wrong keys. Other special keyboards designed to do just one job can be found on children’s toys, games consoles and programmable robots used in primary schools.e ‘keyboard’ could be a picture of a farmyard. Pressing on an animal would cause the computer to make the noise of the animal. A keypad is a block of buttons that contain digits, symbols or alphabetical letters. Keypads can also be found on many keyboards. Mouse You can also move data directly into a computer using a range of input devices.e most common is a pointing input device called a mouse. As you move it along a at surface,the pointer on the screen moves in the same direction.If the mouse has two buttons,the left one is Microphone Scanner Games controller Temperature sensor Mouse Musical keyboard Barcode reader Fig 1.3 Input devices: getting data into the computer
1.2 Input devices and media 9 used to ‘select’items such as text and the right one is used to ‘access’menus.e mechanical mouse has a rubber ball underneath to help it roll smoothly in all directions. e optical mouse uses light to track its movements. e cordless mouse is not physically connected to the computer, but instead uses infrared or radio waves to communicate with the computer. Document scanner A scanner allows you to transfer pictures, graphics and text to your computer.It scans the image from the top to the bottom one line at a time and transfers it to the computer. You can then take that copy and use it in a program, send it as an email attachment or print it. Microphone Data can be entered into a computer through a microphone.e computer responds to this data by carrying out instructions such as printing a document or turning the spoken words into text in a word processor.ese are called voice-activated or voice-response systems. Digitiser Digitisers convert drawings and images into data. For example, a digital camera captures still and video images and stores them in electronic format for printing or editing later. A webcam is a type of digital camera connected to a computer, typically for transmission of still or moving images over the Internet or other network. Some computer users use webcams to see each other while chatting online, or for streaming live video. Other uses of webcams include monitoring trac on highways and other surveillance. Another type of digitiser is found in a graphics tablet, that can capture drawings and handwritten signatures.It is a at, touch-sensitive drawing surface that uses a special pen called a stylus.Images from the graphics tablet are also shown on a monitor. When a transparent digitiser element of this kind overlays a screen it allows direct interaction with the screen. Touch-sensitive devices A touchscreen is another way to input data (Fig 1.4). It is a screen that is sensitive to touch, so you do not need to use a keyboard or mouse. Banks, malls and restaurants use touchscreen kiosks or touch terminals to provide information to the public.Touchscreens are also commonplace on handheld devices such as mobile phones and iPads. Fig 1.4 Touchscreens, such as the one shown here, are popular in public places as there is no need to use a mouse or a keyboard A touchpad is a at rectangular surface which also senses the movement of one or more ngers on its surface.ese devices are usually found on laptop and notebook computers and function as a mouse does to move a pointer. Pointing devices A light pen is similar to a mouse, but is rarely used since touch-sensitive devices have replaced it. A variation of the light pen is a stylus, which is a small pen-like device with a plastic or felt tip that uses pressure instead of ink. A stylus is used to draw on graphics tablets or type on touchscreens to avoid using ngers on the screen. Remote-control devices ese devices send data through signals each time a button is pressed on the device.e signal is received by another device that processes the instruction.
1 Fundamentals of hardware and software 10 Remote control devices are used to change television and radio station channels, open electronic gates and manage slide presentations. Biometric systems ese systems use some part of a person’s body to uniquely identify them.ere are two types of biometric systems that can identify someone. One is related to some aspect of the body using, for example, ngerprints, face or iris recognition (Fig 1.5), as well as the size and shape of the hand.ese characteristics are consistent and rarely change.In contrast, a person’s signature and tone or pitch of voice are related to the person’s behaviour. For example, if you are nervous, then your signature or voice may change. Fig 1.5 An electronic signature can uniquely identify a person Direct data entry (DDE) devices A direct data entry device can transfer information automatically from a document – such as a form or barcode – into the computer. You do not need to enter the information manually. ese devices are used when large volumes of data must be entered into the computer quickly. Previously, it took a relatively long time for a supermarket cashier to add up the cost of your grocery items using a cash register. Nowadays barcode systems make this task much quicker. ere are various DDE devices available. As with manual input devices, dierent DDEs are suitable for dierent purposes. Some examples are explained below. Barcode reader A barcode is a group of vertical bars of dierent widths. Barcodes are found on almost all the products we buy. Groups of bars are used to represent dierent numbers which are often printed above or below the barcode. e numbers normally included in a barcode for a product represent its country of origin, manufacturer and item code.e price is not included in the barcode. Barcodes are read into the computer using a wand or a xed scanner.ere are also camera-based barcode readers. Barcodes are not easily damaged and can normally still be read if they are creased or slightly wrinkled.ey can be printed using a normal printer and ink, and so are cheap to produce. Fig 1.6 A barcode is found on many products A barcode is used to enter data directly into a system. e data collected from barcodes is used to produce customers’ bills and to tell a store what has been sold. Goods can then automatically be re-ordered.ese systems, known as electronic point of sale (EPOS) systems, enable large amounts of data to be input very quickly and accurately. Smart card Millions of people now pay for their shopping using credit, debit or store cards.e magnetic strip on the back of such a card is ‘read’ as it is being ‘swiped’ by a salesperson.is swiping transfers account information and the cost of the goods, into the banking system. is type of system is referred to as electronic funds transfer at point of sale (EFTPOS).
1.2 Input devices and media 11 To gather information from the card, it is swiped through a machine which quickly and accurately reads the magnetic pattern.If the magnetic area on the card is scratched or gets soiled, then the information stored on the card can be corrupted. Such a card is used by businesses to reward loyal customers. A card that does not rely on a magnetic strip is also now appearing.It has a built-in electronic circuit and a set of gold-coloured contacts. Putting the card in a special reader inputs the information held in the circuit. Such cards are called smart cards.ey are more sophisticated than magnetic swipe cards. Although smart cards are often called input devices, they are actually simple storage devices.When the card is put into a machine, data can be read from the card or written onto it. A smart card can store much more data than a magnetic strip. Smart cards, unlike magnetic-strip-based cards, can carry all necessary functions and information on the card.erefore, they do not require access to remote databases at the time of the transaction. Fig 1.7 Smart cards have a built-in electronic circuit and a set of gold-coloured contacts Optical mark recognition (OMR) ere are various ways of inputting letters,words and numbers automatically into a system. For example,when you buy a lottery ticket, you ll in the slip by putting lines through sets of numbers on a grid (Fig 1.8).is slip is then fed into a machine that reads the marks. e computer system turns each set of marks into numbers and enters them into the draw.is method of entering data is called optical mark recognition (OMR) and relies on precisely positioned marks on a form being read by a special scanner.is data is then processed by the system. If you have multiple-choice tests as part of your examinations, you will probably have to answer them on an OMR form.ese answer sheets will be passed through a scanning system to mark your answers.is way of inputting data is fast and accurate. OMR is therefore used to read the data that has been added and then all the data can be transmitted to the computer automatically.e nal information can then be produced without any need for human intervention. Fig 1.8 Data can be entered into a computer in dierent ways. Lottery slips are an example of optical mark recognition (OMR) Optical character recognition (OCR) Another way of entering handwritten or printed text into a computer system is to scan the text using an optical character recognition (OCR) program.e scanned text is turned into a le that can be edited,reformatted and reprinted by a word processor. e accuracy of OCR is variable and can be poor, particularly if the original pages to be scanned are of poor quality. OMR and OCR are often used together in a turnaround document. A turnaround document is one which has some unique information printed on it by a computer with other information which needs to be added to it by a human.It is then fed back
1 Fundamentals of hardware and software 12 into a computer a second time to transfer the added information to the computer. Magnetic ink character recognition (MICR) Banks process millions of cheques each day.Every cheque has the cheque number, account number and branch code printed on it using magnetic ink (Fig 1.9).A magnetic ink character reader (MICR) reads this information along with the amount of the cheque into the banks’ information systems,so that the cheques can be cashed. MICR readers can only read one special font, which includes only numbers and a few punctuation marks. ey can read characters very quickly and with 100% accuracy. Information printed in magnetic ink is also very secure since it is not possible to change the information by writing over it with a pen.e magnetically printed numbers are also not damaged by folding the cheque (as often happens). Both the reader used by MICR and the magnetic ink are expensive. Fig 1.9 Magnetic ink symbols printed on the cheque Sensors e music industry uses musical instrument digital interface (MIDI) systems. Here, data is input through a piano-type keyboard or by sensors that respond to being struck. A wide variety of sounds can then be generated from one keyboard or set of pads. Sensors are available which respond to a wide variety of signals.ey can be used to collect data automatically into a system. For example, the Meteorological Oce has weather forecasting systems that collect data from sensors around the world and in space.ese sensors collect data on temperature, wind speed and direction, hours of sunshine and humidity.is data is processed to help meteorologists to predict the weather. As we know, the forecast is not always accurate, but large amounts of precise data are collected. Information systems use sensors to input data so that the systems can decide what to do.When you approach an automatic door, a sensor tells the system you are there and makes the door open. Burglar alarms use sensors to inform the system when doors or windows have been opened or broken.is causes an alarm to sound or the police to be alerted automatically. Table 1.1 Input devices: advantages and disadvantages (continued) Input device Application Advantages Disadvantages Manual input devices Keyboard (touch) Converts key strokes into binary digits. Carries out the commands of function keys such as ‘End’ and ‘PgUp’ ◆ Used to manually input text into the computer ◆ Used to type commands and instructions to computer systems ◆ Most common means of entering text ◆ Relatively inexpensive ◆ Continued use can cause repetitive strain injury ◆ Errors in transcription are common ◆ Speed of input depends on the user’s experience Mouse (touch) Sends positional information to the computer, by clicking or scrolling of mouse buttons ◆ Acts as an interface between the user and the computer ◆ Used to issue commands directly to the computer ◆ Commands can be given directly to the computer (e.g. page down) ◆ Can activate commands by selecting icons directly ◆ Hand-to-eye coordination can be a problem ◆ Shifting between keyboard and mouse can be confusing
1.2 Input devices and media 13 Input device Application Advantages Disadvantages Joystick (touch) Similar to a vehicle gear shift, but with buttons for different commands ◆ Generally used in game playing ◆ Ideal for games such as car racing and combat ◆ User has to become skilled at the sensitive movement of the joystick Touchscreen (touch) Allows the user to press parts of the screen to activate different functions ◆ Are located in public places such as restaurants and shopping malls where transactions can be made and information given ◆ Easy way to input options and choices ◆ Can be used by children and the physically challenged who are unable to use other input devices ◆ A limited number of values can be displayed on one screen at a time ◆ More expensive than a standard monitor Scanner (light) Used to capture an image in hard-copy and create a digital copy of the image ◆ Conversion of hard-copy imagesto soft-copy can be used to import and export documents and images across different applications ◆ Relatively cheap and easy to install ◆ Depending on use, flatbed or handheld scanners can be chosen ◆ The quality of the image depends on the quality of the hard-copy, scanner and scanner software Graphics tablet (machine-readable) Used to input lines and shapes through pressure and movement of a stylus on the tablet ◆ Captures input like handcreated drawings and signatures ◆ Resulting images can be displayed on a monitor ◆ Allows artiststo sketch detailed digital drawings more easily than by using a mouse ◆ Can be used to capture signatures as a biometric ◆ Requires some practice ◆ More expensive than a mouse Voice-recognition system (sound) Data that is input in audio form. The input is analysed for commands which are then processed ◆ Allows users to dictate text or give commands directly to the computer ◆ The user can speak normally for dictation ◆ Must be trained to recognise voice patterns ◆ Software cannot interpret all English meanings Direct data entry devices Barcode reader (light or laser) Barcodes are groups of bars of different widths and are found on almost every product you buy. The codes are read into the computer using a wand or a fixed scanner ◆ Different groups of barsrepresent different numbers. These numbers represent the product's country of origin, manufacture and item code ◆ Data can be input much faster than it takesto be keyed in ◆ Not easily damaged ◆ Can be printed using a normal printer and ink and so cheap to produce ◆ The order of the data stored cannot be changed easily Electronic Point of Sale (EPOS) (laser) Data collected from thebarcodes is used to produce information and update the database ◆ Used to record transactions and track inventory ◆ Prices of products can be easily updated ◆ Items can be easily scanned ◆ Depends on a reliable Internet connectivity Optical Character Recognition (OCR) (light) Text and graphics are scanned as soft copy ◆ Can be used to input large blocks of typed text ◆ Can speed up the typing process ◆ Accuracy of the text can be poor (continued) Table 1.1 Input devices: advantages and disadvantages (continued)
1 Fundamentals of hardware and software 14 Input device Application Advantages Disadvantages Magnetic ink character recognition (MICR) (magnetic) Data is printed as special characters using magnetic ink. This data is translated into text or values ◆ Used by banks to process cheques, by printing additional bank details (branch, account number) ◆ Is quick and highly efficient ◆ Both humans and machines can interpret the data ◆ Not easy to forge ◆ Has limited applications ◆ As the use of cheques becomes obsolete, its use is in decline Optical Mark Recognition (OMR) (light) Relies on the presence or absence of precisely positioned marks on a form being read by a special scanner. This data is then processed by the system ◆ Popular with lotteries and multiple-choice question sheets issued by examination boards ◆ Data input is very fast and accurate ◆ There is a limit to the number of responses ◆ Incorrect or inconsistent marking on the sheet may result in the data being rejected Smart card (magnetic) A magnetic strip containing encoded data about the owner of the card is placed on a plastic card ◆ Used to store data on debit, credit, loyalty, phone and other cards ◆ Can be used to store financial transactions ◆ Transactions are fast ◆ Saves the user from carrying cash ◆ Can be damaged ◆ May soon be replaced by embedded microchips Musical Instrument Digital Interface (MIDI) (sound) Can be used by musicians to create, manipulate and store sounds in a computer ◆ Used to store music from instruments or voice for editing ◆ Once stored, the data can be arranged in many ways ◆ Special software must be used to translate the music into a musical score Table 1.1 Input devices: advantages and disadvantages (continued) Questions 1 What is the general name for each of the following devices: a transfers data from the outside world into a computer b a at rectangular surface which also senses movement of a nger on its surface c a system that uses some part of a person’s body to uniquely identify them d transfers pictures, graphics and text to a computer e transfers information automatically from a document, such as a form or barcode into the computer f relies on precisely positioned marks on a form being read by a special scanner g a document which has some unique information printed on it by a computer, but other information needs to be added to it by a human before it is fed back into the computer. 2 What is the general name for each of the following processes: a data is entered or transferred into the computer by hand b to send data at a distance through signals each time a button is pressed on the device.
15 Output devices 1.3 To get processed information out of a computer, you may need an output device. ‘Output’ means to show, print or store the results of processed data.e most common types of output are: ◆ Soft copy: this is not permanent.It includes output from a computer monitor, audio (sound) from speakers, electrical signals and output from one computer to another. ◆ Hard copy: this is also called permanent output since it is printed for you to review away from the computer. Examples are printed reports and pictures. Display devices Computers usually display output on a screen or monitor. Some monitors are separate and need to be plugged into the computer’s system unit. Others, such as laptops and mobile devices, have their screens integrated to the system unit and keyboard. Televisions can also be used as computer monitors with some additional connections. Other display devices include interactive whiteboards (also called smartboards) used for teaching or presentations. ese large touch-sensitive plastic boards respond to input either directly by connections to a computer or through other devices such as a projector, tablet or magnetic pen. e most common types of display device include LCD (liquid crystal display) atscreens and LED (light-emitting diode) screens on handheld devices and laptops. A monitor contains a matrix or array of bright dots of red, green and blue (known as RGB).ese can be blended to display millions of colours. Mapping the location and colour information of each bit of data creates a computer image.is is known as a bitmap (bmp).e bitmapped image seen on a monitor is made up of thousands of pixels. Pixel stands for picture (pix) element. Features of a computer screen include its size and resolution. Fig 1.10 Various types of devices with displays Features of a computer screen Size is is the dimension of the screen which shows the output. Common desktop screens are from 14 inches to 19 inches measured diagonally. Larger sizes are now available. Resolution is determines how clear and detailed the output on the screen can be. Pictures on a screen are made up of tiny dots (one dot = 1 pixel).e more pixels per inch, the clearer and more detailed the graphic. Colour e number of colours displayed can vary from 16 to 256 to 64 thousand to 16.7 million.e more colours, the smoother the graphics appear, especially photos. Cursor/pointer e cursor is a symbol that shows where you are working on the screen.It may appear as for text and for the mouse pointer location. Scrolling is allows the text or graphic to be moved or up or down or brought into view on the screen.
1 Fundamentals of hardware and software 16 Printing devices No matter how simple or complex the data-processing operation is, the nal result must be made available in a user-friendly form, and usually in the form of a permanent record. Printers are devices which output a hard copy of your work.e choice of printer depends on the speed, quality and quantity you want, and the cost. Some printers also perform the functions of a scanner, a photocopier and fax machine.Two main categories of printer are impact and non-impact. Impact printers Impact printers strike through a carbon or inked ribbon, like a typewriter.ey are noisy and do not usually print acceptable graphics. However, they are useful for printing multiple copies using carbon paper, and printing payroll or nancial reports that require continuous sheets of paper perforated to tear into individual sheets if necessary.Impact printers are largely obsolete now. However, there are still some dot-matrix printers in existence. Dot-matrix printer A dot-matrix printer uses pins to print a pattern of dots on paper.e main advantage of using dotmatrix printers is for printing multiple copies using carbon paper.e main disadvantage is the relatively poor quality of printing, which can be read but cannot be used for reproduction or for business letters. Non-impact printers ese printers do not involve actually striking the paper.Instead, ink spray or toner powder is used.e characters are then xed onto the paper by heating, for example. Because the printing element is simple and has no moving parts, these printers are inexpensive to manufacture and print quickly and quietly. Inkjet printers It is now possible to buy low-priced, good quality printers that can print in both black-and-white or colour.e quality of printout can be nearly as good as that of a laser printer, but inkjet printers are slower depending on what is to be printed. Speeds of 4 to 6 pages per minute may be achieved.eir cartridges need to be replaced more frequently than the toner cartridges of laser printers. Colour inkjet printers are ideal for use at home, where small-quantity output is required for greeting cards, photographs and school work. Ordinary paper can be used. Laser printers Laser printers produce attractive documents at a high resolution and are much faster than inkjets.ey are used in many workplaces because they are quiet, print quickly, can be stocked with a large number of sheets of paper, and produce very high quality documents. e printout from most laser printers tends to be 300 to 1200 dots printed per inch (dpi). Many lines are printed simultaneously, and speeds of 8 to 12 pages per minute can be attained. Colour laser printers are also available.ey are far more costly to buy than colour inkjet printers, but produce higher quality images and are cheaper to run. Thermal printers ermal printers use heat on chemically treated paper to form characters. Many automatic banking machine (ABM) receipts, debit or credit card slips and even some ultrasound scanned images are printed using thermal printers.ese printers are quiet and more recent ones print quickly. However, the paper is expensive, and the print eventually fades if exposed to light or heat. 3D printers ree-dimensional (3D) printers are similar to inkjet printers, but instead a 3D model is created layer by layer, from the bottom upward.e model is created over many hours, as each layer is printed on top of another. However instead of using ink as with the inkjet, the 3D printer uses melted plastic that sticks each layer to the previous one.
1.3 Output devices 17 Fig 1.11 3D printers create a model layer by layer Plotters Car designers, architects and engineers who wish to print accurate charts, diagrams and 3D drawings, output not to a laser printer but to a plotter. A plotter uses coloured pens or toner to draw an image on paper (Fig 1.12).e paper is handled in dierent ways depending on the type of plotter. Flatbed plotters hold the paper still while the pens move. Drum plotters roll the paper over a cylinder, while pinchroller plotters are a mixture of the two.e advantage of a drum plotter is that it can produce very large drawings. Fig 1.12 A plotter can produce very large drawings Audio devices Most computers sold to homes and schools include a sound card.is allows both the recording (input) and playback (output) of sound. Microphones record sound while loudspeakers can play sound to a group of people (Fig 1.13), however, headphones are more popular for users who wish to listen to the sound without disturbing anyone around them (Fig 1.14).ese devices are small speakers that need to be placed close to one or both ears. Earphones or earbuds are very small headphones that t inside the ear. A headset is a set of headphones, which has a microphone attached to allow you to speak and listen at the same time. Fig 1.13 Microphones record sound while loudspeakers play back sound Fig 1.14 Headphones, headsets and earbuds are more popular for users who wish to listen to the sound without disturbing anyone Sound may also be output from a digital le or as music from a CD. Some software applications will allow word-processed text to be read back to the user. is can be very important to young children or the visually impaired.
1 Fundamentals of hardware and software 18 Questions 1 State three general types of output devices. 2 What is the general name for each of the following descriptions: a tiny dots that make up the pictures on a screen b devices which output a hard copy of your work c type of printer that is useful for printing multiple copies using carbon paper d type of printer that uses heat on chemically treated paper to form characters e a printer that uses melted plastic that sticks each printed layer to the previous one f very small audio output devices that t inside the ears. Modem COMPUTER Speakers Inkjet printer Monitor Plotter Robot Headphones Laser printer Traffic lights Dot-matrix printer Fig 1.15 Output devices: getting data out of a computer
19 Primary memory 1.4 Some of the data you put into a computer will be needed right away for processing,while other data may not be needed for long periods of time.erefore, dierent methods of storage are appropriate for dierent uses. e main purpose of the CPU is to process instructions as quickly as possible. Main memory is located directly on the computer’s main circuit board so that data can travel quickly to and from the CPU to be processed. Main memory is located directly on the computer’s main circuit board so that data can travel quickly to and from the CPU to be processed. Data stored at a specic memory location (called an address), can have its address contents accessed to be read from, written to or processed.e largest amount of data which can be moved together to be processed is called a word ere are dierent types of computer memory. Let us look at some examples of computer memory and their features. Types of memory Random-access memory (RAM) Inside a computer you will nd one or more memory chips called RAM (random-access memory).ese hold the temporary operating instructions for the computer, its programs and the data.is is the place where the CPU receives the instructions and data it needs to do its job. e advantage of RAM is that the computer can access data held in RAM almost immediately.e major disadvantage is that RAM is volatile – data held in RAM is lost when a computer is turned o or malfunctions.is is why we need to use other media to store data. As computer programs and operating systems have become more complex, the size of RAM has increased. Most computers come with 2 to 8 GB of RAM as standard. Fig 1.16 Random-accessmemory (RAM) – a close-up of a RAMmemorymodule Read-only memory (ROM) When a computer is made, basic input/output instructions are put on ROM (read-only memory) chips.ese instructions can be read, but not changed (non-volatile), and are available every time the computer is switched on. Hybrid memory Recently, as memory technology develops, the line between RAM and ROM has become blurred. Now, several types of memory combine features of both. ese devices do not belong to either group; they are called hybrid memory devices. Hybrid memories can be read and written as desired, like RAM, but maintain their contents without electrical power, just like ROM. Flash memory is a variation of a ROM device that is typically used to store code.
1 Fundamentals of hardware and software 20 Questions 1 Describe the main purpose of the CPU. 2 What is the general name for each of the following types of memory: a holds the temporary operating instructions for the computer b instructions can be read, but not changed, and are available every time the computer is switched on c can be read and written as desired, but maintains its contents without electrical power. 3 State the name given to the smallest chunk of information or piece of data that a computer can work with. How data is represented Everything that the computer does results from the turning on and o of dierent combinations of microelectronic switches called transistors or bistable devices.e ‘o ’ and ‘on’states of the transistors are used to represent the zeros (0) and ones (1) that make up the binary number system.ese zeros and ones are known as bits (binary digits). A bit is the smallest chunk of information or piece of data that a computer can work with – either binary 0 or binary 1.e more bits a processor can use, the faster it can compute (work things out) and the more memory it can access easily.When you use a computer, millions of switches are continually being switched on or o by an electric current. A popular range of processors is the i5 or i7 series produced by Intel.e chip shown in Figure 1.17 is made up of over 27 million tiny switches (transistors) mounted on a slice of silicon. Fig 1.17 A close-up of an Intel i7 core processor If you think of all of the programs on a computer, plus all the les that are saved, you can see that on each computer disk there are millions of bits. Computer memory and storage size is therefore given in bytes (8 bits make 1 byte), kilobytes (kB), megabytes (MB), gigabytes (GB) or terabytes (TB). ‘Kilo’ normally means a thousand, or 10 3 . However, 1 kilobyte is 1024 bytes.is is because computers count by twos (binary) and powers of 2 and not in tens like humans.erefore, 1024 is 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2, that is 2 multiplied by itself ten times. Table 1.2 Units of computer data storage 1 kilobyte (kB) = 2 10 = 1024 bytes 1 megabyte (mB) = 2 20 = 1024 kilobytes = 1024 × 1024 bytes = 1 048 576 bytes 1 gigabyte (GB) = 2 30 = 1024 megabytes = 1024 × 1024 kilobytes = 1024 × 1024 × 1024 bytes 1 terabyte (TB) = 2 40 = 1024 gigabytes = 1024 × 1024 megabytes
21 Secondary storage 1.5 Secondary storage refers to the media and methods used to keep programs, data and information available for later use. Secondary storage saves programs and data permanently, whereas primary storage uses main memory, which is temporary. Devices and media Secondary storage media keep data, instructions and information on the physical hardware of a computer for future use. Examples are hard disks, compact disks and tapes. Storage devices record and retrieve data, instructions and information to and from storage media. Examples are hard disk drives, compact disk drives and tape drives. So hard disks are storage media whereas hard disk drives are storage devices. It is very important to have media and methods to store data and programs when a computer is turned o. Secondary storage can be generally grouped into local storage and cloud-based storage. Local storage Local storage involves users having storage devices or media with data in their possession or generally knowing of their location.ese local storage devices include: ◆ magnetic media such as magnetic tape and hard disks ◆ optical disks such as CD-ROM, CD-R, DVD and Blu-ray ◆ ash memory. Magnetic media e cheapest way to store and back up data is on magnetic media, such as magnetic tape and hard disks. Magnetic tape Backing up to tape is vital for computer networks and organisations or businesses which need to store important and large amounts of data for a long time. Magnetic tape is a narrow strip of plastic coated with ferrous oxide.e data is recorded along the length of the tape, with each symbol encoded in binary form across the width of the tape. It is unique since data can only be retrieved in the same order in which it was stored.erefore, retrieving the 50th piece of data means accessing 49 pieces that precede it.e tape drive winds the tape from one reel to another by passing the tape over a magnetic head to read, write or erase the data as it moves (Fig 1.18). Magnetic tape is used primarily as a back-up storage medium since access to data is not as rapid as with other storage devices. Since creating a tape backup is a slow process it is often done at night or at the end of a working day. Fig 1.18 Backup tapes such as this are used to make copies of large amounts of data on computer networks Hard disks Another common device that stores data is a magnetic disk known as a hard disk (Fig 1.19). Although it is possible to add external hard drives, most are inside computers, protected by rigid cases. Technically, the hard drive is the machinery that controls the motion of the hard disks which contain the data. But most people use ‘hard disk’ and ‘hard drive’ interchangeably.
1 Fundamentals of hardware and software 22 Fig 1.19 Structure of a hard drive Hard disks are popular for use with computers and laptops since they store a large amount of data. Hard disks ranging from 700 GB to 1 TB in capacity are now common. External hard disks are now available in capacities and speeds similar to internal disks. Optical disks Optical disks can store much more data than most magnetic media.ere are three basic types of optical disk. Compact disk drives are also known as optical disk drives because they use lasers to store and read data. You will already be very familiar with one type of compact disk – the audio CD that plays your favourite music.ere is, though, another type of CD that is used only with computers.is is known as the CD-ROM (Compact Disk Read-Only Memory). e CD-ROM allows you to access up to 650 MB of stored data. Many computers with CD-ROM drives can play audio CDs, but the term CD-ROM is always taken to mean any CD format which stores data, rather than audio tracks. CD-ROMs are read-only media, which means that you can only use the data on the disks. CD-ROMs that contain software or programs are of the Write Once Read Many (WORM) variety.ey cannot be changed once they are created.is is where the ROM part of their name comes from. e major advantage of optical drives such as CDROMs is that they can store signicant amounts of data. However, they can be easily damaged during handling and from exposure to light, heat or dust. Compact Disk Recordable (CD-R) and Compact Disk Rewritable (CD-RW) are types of CD that allow data to be written to (stored on) disks. However, the data on CD-RWs can also be erased. Many personal computers are sold with CD-R drives so that you can regularly back up data saved on hard disk. Digital Versatile Disks (DVDs) are used for storing any kind of digital data and gaming software.ey can store much more data than CD-ROMs, enough that full-length feature lms can be put on DVD.ey are known for replacing the VHS cassette tapes which were used to distribute movies, and as a result, DVDs are often referred to as digital video disks. A DVD-Video holds video programs and is played in a DVD player linked to a TV or monitor. DVDROM, like CD-ROM, holds computer data and is read by a DVD-ROM drive linked to a computer. e massive storage capacity of DVDs, coupled with the fact that digital technology produces better pictures, are the main reason DVDs replaced videotapes. Blu-ray Disks (BD) were designed to replace the DVD by storing several hours of video using a storage capacity of up to 100 GB. Its main use is for distribution of video game software and feature lms that can be viewed in high-denition resolution. Flash memory USB (Universal Serial Bus) ash memory drives are also known as jump drives, memory sticks or ash drives, and can be convenient alternatives to
1.5 Secondary storage 23 Flash memory cards ese cards are inserted into digital cameras, video games consoles, laptop computers, MP4s, digital cameras, mobile phones and other music players. Mobile phones, for example, contain a Subscriber Identity Module, also called a SIM card, that stores the phone’s unique number, along with data such as contact numbers and text messages.ese cards vary in size, and their storage capacity ranges from 2 GB to 1 TB.e various devices, however, dictate the appropriate type and size of memory card it uses, so many are not interchangeable. Fig 1.22 Flash memory cards vary in shape, size and capacity and can be used in a range of devices Cloud-based storage Cloud-based storage involves storage of data by users on multiple computers anywhere in the world.e exact location of this data is not known by its owners. If you have used Facebook,Twitter,Instagram or YouTube, have an email address with Gmail or have used a mobile app, then you have probably used cloudbased storage already. e cloud is an unlimited and powerful remote network of interconnected specialised computers. You can store your data such as school work, photos, email messages and videos at any time, from anywhere, once you have access to the Internet.is saves you from deleting data from your secondary storage device or Fig 1.20 Optical disks can store large amounts of data and typically used for storing digital data, movies and gaming software hard drives.eir storage capacity is typically 8 to 256 GB, although there are larger capacities available. ey can be used for storage and data backup, but are mostly used for transfer of computer les, since they can store and transfer data faster than the CD and can be read by many devices. Flash memory drives combine the best features of the memory devices described thus far.ey store large amounts of data, are low cost, non-volatile, fast (to read, but not to write), and electrically reprogrammable.ese drives have become increasingly common since they use a standard-type USB connection with computers and laptops. Fig 1.21 Memory sticks provide additional storage, and are non-volatile and faster than most magnetic and optical storage media
1 Fundamentals of hardware and software 24 transferring it to other storage devices to free space. When you use cloud-based storage, the data is not stored on a single remote computer somewhere in the world, but on lots of dierent computers.If one computer stops working, your data is still stored on another one. Some cloud-based storage is free. For example, Dropbox and Google Drive give users access to about 15 GB of storage. However, businesses pay to have their data stored in the cloud for easy access and backup purposes. Users pay for the data storage, which can change as the amount of their data increases. You may never know where your data is stored, but you can access it using your computer or other devices and applications. With cloud-based storage, millions of people from anywhere in the world can interact with the application at the same time. Access to data is immediate once they have access to the Internet. As with any type of storage, there is always the risk of your data becoming accessed, deleted, stolen or corrupted, whether as an error or a deliberate act. Users with similar email addresses can receive each other’s messages. Storing sensitive data in the cloud can also be a security concern. Table 1.3 Storage devices: advantages and disadvantages Storage Advantages Disadvantages Magnetic media Hard drive Storage capacity: many gigabytes and getting larger ◆ Stores and retrieves data quickly ◆ External hard drives are portable ◆ Internal hard drives are not portable Tape Storage capacity: many terabytes ◆ Used to back up data on hard disks ◆ Low-cost storage ◆ Not generally used with desktop computers ◆ Slow – so only used for network back-ups Removable hard drives Storage capacity: many gigabytes and getting larger ◆ Removable and portable ◆ Relatively cheap ◆ Can be misplaced, or damaged since they are portable ◆ Need specific cable to connect to computer or device Flash memory Storage capacity of USB memory stick: typically 8 GB to 256 GB Storage capacity of memory card: 2GB to 1 TB ◆ Compact shape ◆ Operates faster than an optical disk ◆ Can hold more data than an optical disk ◆ USB memory stick requires a USB port ◆ Some do not have write-protection ◆ Can be easily misplaced or stolen Cloud-based storage Storage capacity: 15 GB for individual users of some applications. Limitless for others who pay for the service ◆ Users from anywhere in the world can interact with the application at the same time ◆ Data can be accessed, deleted, stolen or corrupted (continued)
1.5 Secondary storage 25 Storage Advantages Disadvantages Optical storage CD-ROM (Compact disk read-only memory) Storage capacity: 650 MB ◆ Very cheap to produce, particularly on a large scale ◆ Good way of distributing software ◆ As CD is read-only, data cannot be changed or deleted ◆ Slower access times than hard drives CD-R (Compact disk recordable) Storage capacity: 650 MB ◆ Possible to add data (write) to the CD-R in more than one session ◆ Good for backing up files ◆ Should have a CD-R recorder to write to a disk ◆ CD-R software has varying capabilities CD-RW (Compact disk rewritable) Storage capacity: 650 MB ◆ CD-RW can be erased and reused as many times as required ◆ Good for backing up files ◆ Should have a CD-RW recorder to write to a disk ◆ CD-RW does not work in all CD players DVD (Digital versatile disk) Storage capacity: 4.7GB up to 17 GB ◆ Excellent for showing video ◆ As with CD-R and CD-RW, there is a range of ways of writing (storing) data on DVD ◆ Has replaced CDs, producing better quality videos than CD-ROMs ◆ DVDs do not work in CD-ROM drives Blu-ray Storage capacity: 25GB up to 100 GB ◆ Blu-ray was intended to replace the DVD. Main use is for distribution of feature films and video games ◆ Can be viewed in a high-definition resolution ◆ Requires a Blu-ray player or optical drive ◆ More expensive than CDs and DVDs Table 1.3 Storage devices: advantages and disadvantages (continued) Questions 1 State the general name for the type of storage that saves programs and data permanently. 2 List three categories of local storage. 3 What is the main use of magnetic tape? 4 What type of secondary storage is most suitable for use in digital cameras and mobile phones? 5 Explain one advantage of, and one concern associated with using cloud-based storage.
26 1.6 System software System software is the name given to the software that controls hardware and how all other software works. Examples of system software include operating systems and utility software. Operating system e most commonly used system software is called an operating system.Without an operating system, a computer would not work. Popular operating systems include Microsoft Windows 10, Apple’s Mac OS X and many versions of LINUX. Popular mobile operating systems include Apple iOS and Google Android. Fig 1.23 Common operating system logos: from left to right they are Apple, Windows, Linux and Android Booting e process of starting a computer is known as booting.e rst thing a computer does when you turn on the power button is to check that it is working properly by following certain instructions held on a ROM chip known as the BIOS.It will then look for an operating system to tell it what to do next.e operating system is loaded from disk to the computer’s random-access memory (RAM). Hardware control e operating system supports tasks like accepting input and transferring data between primary and secondary memory or displaying output.It also sets the rules for controlling hardware resources such as peripheral devices like keyboard and mouse, the amount of memory used, CPU time allocation and disk space used. Software control e operating system controls how all software applications, games or other programs work on the computer. Memory management When a program or data is too large to t into main memory, a method called virtual memory can be used to split the program into manageable blocks.e required blocks are swapped between main memory and secondary storage to accommodate the program or data. Input/output management Since each device has a program called a driver that allows the device to communicate with the computer, the ow of information among devices must be managed and coordinated. Process management Process management allocates time for processes to use the CPU, checks on processes waiting to use the CPU, and signals when the CPU is available. File management Files need to be saved, copied, renamed and deleted. A le manager checks the amount of memory needed to perform these tasks and manages the organisation of the les in secondary storage. Utility software Utility software is specialised software that tries to protect and maintain the system software. Examples include protecting software against damage caused by computer viruses, backing up les and recovering les after software has stopped working (crashed). Questions 1 Explain the purpose of system software. 2 Name one computer operating system and one mobile operating system. 3 State the name of the term that matches the following descriptions: a the process of starting a computer b a method used to split a program into manageable blocks.
27 Data processing 1.7 Data must be processed by the most suitable means. It can then be transferred to one or more computer systems for more processing, for output or for storage. Batch processing A batch processing system is one where data is collected together in a batch before processing starts. Batch processing is most suitable for tasks where a large amount of data is processed on a regular basis. When a batch job begins, it will continue until it is completed, or until an error occurs. Examples of batch processing systems include those that process utility bills such as water and electricity, payroll systems and examination report card systems. Credit card companies also process billing in batches.e customer does not receive a bill for each separate credit card purchase but one monthly bill for that month’s purchases.e bill is created through batch processing, where all the data is collected and held until the bill is processed as a batch at the end of the billing cycle. Advantages ◆ Once the data is submitted for processing,the computer may be left running without human interaction. ◆ Jobs can be scheduled for a time when the computer is not busy. Disadvantage ◆ ere is always a delay before work is processed and returned since batch jobs are usually stored up over a period of time. Time-sharing A time-sharing system allows many users to share time on a single computer. Each user is given a slice of CPU time by the computer.e computer works so fast that each user seems to be the sole user of the computer. One example of a time-sharing system is a bank’s bankcard system, which allows hundreds of people to access the same program on the mainframe at the same time. Other operating system controls include: ◆ multi-tasking: allowing more than one program to run (work) at the same time: for example, using a desktop publishing program while a graphics program is still running ◆ multi-processing: executing programs using two or more processors simultaneously ◆ multi-programming: executing two or more programs at the same time using only one processor ◆ multi-user: allowing more than one user on a computer network to access the same le at the same time. Online and real-time processing Computers and peripheral devices are online when they are connected to a main processor and turned on, so that the operator can interact with them. Printers are online, for example, when they are ready to receive data from the computer to print. Most printers have an online button you can press to turn the machine on. If it is turned o, then you are oine. You can also be online if you are connected to, say, the Internet through a modem or network. A real-time processing system processes data without signicant delay, making it always up-to-date. Since a processing system must be connected to one or more computers to process data, then it must also be online. However, note that online does not necessarily imply that processing is real-time since there may be some delay with an online system. Examples of real-time processing systems include aeroplane landing control systems, electronic fund transfer systems and ticket reservation systems. Advantages ◆ No signicant delay for response. ◆ Information is always up-to-date.
1 Fundamentals of hardware and software 28 Disadvantages ◆ e computer must be dedicated solely to the task. ◆ e computer must be continually online. Data transfer Most computer users will, at some time or another, need to transfer les between computers. School students may need to transfer their work from a computer at home to the school network via cloudbased storage, by using a secondary storage device such as a ash memory stick or by emailing the work to themselves to retrieve when they are at school. Uploading data involves transferring data from your computer to another computer on the network or the Internet, while downloading involves receiving data to your computer from another computer on the network or the Internet. Updates to software packages, such as Microsoft Oce, are downloaded from the Internet using le transfer protocol (FTP) (see section 3.2). Before transferring data, it is also sometimes necessary to reduce the le size.e process of reducing the size of a le for storage, or for sending via the Internet, is known as le compression.WinZip and Winrar are popular programs for compressing les.ey can also be used to group les together into a single le for easier transmission. File compression is important because some les can take up a large amount of disk storage space. e larger the le size, the longer it takes to send via the Internet. Users of the Internet will also know that web pages containing pictures can take a long time to load. Some popular le formats give smaller le sizes than others because they are a compressed le type (Table 1.4). Table 1.4 File compression Type of data to be compressed Compressed le format Graphics ◆ JPEG (Joint Photographic Experts Group): a common image file found on computers and the Internet ◆ PNG (Portable Network Graphic): a common image file format to find on a computer and the Internet Music ◆ MP3: a digital audio file for listening to music on computers and digital media devices Video ◆ Versions of MPEG (Moving Pictures Experts Group): MP4 files can also contain audio, video, images, and text data Questions 1 State the most suitable type of processing mode for each of the following examples: a printing 400 cheques for employees’wages b a computer that can access the Internet c a printer is plugged in and turned on. 2 State the most suitable term for each of the following descriptions: a transferring data from another program to the one you are using b the process of reducing the size of a le and/or combining les for storage or transmission. 3 Suggest the most suitable compressed format for each of the following les: a a picture of a family b a video of a birthday party c a recording of a song by a school choir.
29 Application software 1.8 You have seen that an operating system such as Windows is essential for a computer to work. Most of the software we use regularly has been created to do specic tasks – for example, word processing or desktop publishing.e term for software such as this is application software or an application program. Application software is dened as any program that enables the computer to carry out one or more specic tasks. General-purpose software e most popular applications are those that are not specic to any organisation or business and can be used by anybody.e programs you use at school or home – for word processing, databases, spreadsheets, presentations, drawing and painting – will be such programs.ese programs are known as generalpurpose software, because the user decides what to use the software for. For example, you might want to use a word processor to write a letter, or to design a poster for a school play. number of years and is generally error (bug) free. Some applications are even available online, where information can be accessed anywhere or updated by multiple users at the same time. Popular examples of application programs (software) are given in Table 1.5. Customised and custom-written software Customised software is general-purpose software that has been modied to perform specic tasks for the user.Word-processing, spreadsheet and database programs are examples of general-purpose software that can be customised by automating certain parts of the software or writing and adding programming modules to perform specic tasks. In contrast, custom-written software, which is also known as bespoke or tailormade software, is software written for use in specic organisations such as the military, in hospitals for medical equipment, or in banks and other nancial institutions.It also involves specic training,since users need to be able to use it eciently. Other examples of tailormade software include that used by air trac controllers, who manage the ights of thousands of aircraft; accounting software; airline reservation software; and computer-aided design.ese are not general-purpose,since the users of these kinds of software (for example, accountants and engineers) are trained in a particular eld of expertise. Since this software is specic to an organisation or business it can be very costly to create and may take a long time to write before it can be used. Specialised software Specialised software is written solely for a specic task rather than a range of functions. Examples include the software on your mobile phone for your camera.It will only allow you to manipulate and share the photos. Another example would be an online card game, which would only allow you to play that particular game. Fig 1.24 Data in online applications such as Google docs, sheets and slides can be updated in real time and shared with multiple users General-purpose software is much cheaper because it has been used by millions of people over a
1 Fundamentals of hardware and software 30 Integrated software Many computers are sold with integrated software already installed.Integrated software is the term for a program that includes all the major types of application (for example, word processing, spreadsheet and database) and brings them together into a single software package. Microsoft Oce and Adobe Creative Suite are examples of integrated software. e large software companies such as Microsoft sell their main application programs together in one package. Although packages such as these are sold as integrated software, it is not true integrated software, as the programs are also still separate applications. Choosing software should be no dierent from choosing any tool for a job. Just as in construction, you decide whether to use a drill or a hammer to carry out a particular task, so with software you need to decide what it is you actually need to produce, and then choose the most appropriate program.is is very important when choosing programs to use for your coursework. Table 1.5 Popular application programs Type of software Examples of application programs Purpose Word processing Microsoft Word, Google Docs Writing letters, reports and other documents Desktop publishing Microsoft Publisher, Google Slides, Adobe PageMaker Producing newsletters, leaets and posters Databases Microsoft Access Searching and sorting data Spreadsheets Microsoft Excel, Google Sheets Commonly used for nance, budgeting and so-called‘number crunching’. Also used for creating models, simulations and‘What if?’ queries Graphics Microsoft Paint, Adobe Photoshop, Adobe Illustrator, Adobe InDesign Painting and drawing Computer-aided design (CAD) AutoDesk AutoCAD, DesignCAD Producing detailed plans or models, often in 3D. Used by engineers and architects, e.g. for plans of buildings or in the design of cars Integrated software Microsoft Oce, Adobe Creative Suite All the major application programs – word processing, spreadsheet and database – are closely related and the output from the various programs can be transferred or embedded into each other with minimal errors Presentation software Microsoft PowerPoint, Prezi Delivering slideshows and presentations to an audience – normally using a large screen Questions 1 State the most suitable term for each of the following descriptions: a software that is written for use in specic organisations b software that is written solely for a specic task rather than a range of functions c a program that includes all the major types of application. 2 Name two applications that can be used online and shared among users. 3 What type of application software would you use for: a creating presentations b monitoring weather patterns for the Meteorological Oce.
31 User interfaces 1.9 User interfaces are found wherever digital technology exists. How you interact with and use this technology is controlled by the computer–user interface, also known as the human–computer interface (HCI). A user interface involves various ways of capturing or transferring data between a user and the computer system.e interface therefore can be graphical, text-based, or even audio–video-based, depending on the application, meaning that it can be a hardware interface, software interface or a combination of both. Since a user interface helps the user to interact with a system, it should: ◆ have an attractive design ◆ be simple to use ◆ have a quick response time ◆ have instructions that are easy to understand ◆ have a consistent layout if there are multiple screens. Hardware interfaces Hardware interfaces such as touchscreens, sensors, digital cameras and special keyboards are input devices that were discussed earlier in the chapter. An example of a hardware device with a user interface is a games controller (Fig 1.25).e layout of the buttons, touchpad, joysticks and hand grips together form the user interface that carries out the various functions. Fig 1.25 Hardware interfaces include games controllers with buttons that perform various functions Software interfaces Software interfaces are available after the computer has booted up and the operating system has been loaded, allowing the user to interact with the computer or device through an interface. Software interfaces include online forms for data entry, dialogue interfaces such as navigational systems in some vehicles and Amazon’s Alexa on their talking Echo speaker unit. ere are four main types of software interface: ◆ command-line interface ◆ menu-driven interface ◆ graphical user interface (GUI) Command-line interfaces Command-line interfaces require you to type in commands using a special language.is special language makes command-line interfaces dicult to use, especially for new computer users.In recent versions of Windows, it is called Windows PowerShell (Fig 1.26). Fig 1.26 An example of a Windows PowerShell command-line interface Menu-driven interfaces A menu is a list of options from which you can choose what you want to do. Application programs use menus as an easy alternative to learning program commands. Menu-driven interfaces were developed to try to
1 Fundamentals of hardware and software 32 make the interface friendlier and easier to learn. You can control the computer by choosing commands and available options from a menu, using the keys on a keyboard or a mouse. For example, depending on your choice, another set of options may appear on the screen for you to make another choice (Fig 1.27).is continues until you reach your nal selection. Fig 1.27 Menus allow you to make a series of choices from a list which produces another list until your nal selection Menu-driven interfaces can also be verbal rather than visual.An example is an automated answering service, where you press 1 on the keypad for a department, 2 for another department, or 0 for the operator.ese interfaces can be easy to follow but can become confusing as the number of menu options increase and you need to retrace your previous options. Graphical user interfaces All computers are now supplied with a graphical userinterface (GUI) installed because it is presently regarded as the type of user interface which is easiest to use.e main features of a GUI include its ease of use for beginners, and ability to cut and paste or ‘drag and drop’ data and les among applications. However, GUIs require a lot of memory,which can slow processing time. Sometimes simple tasks take longer than necessary because of the number of functions or steps required. A GUI comprises Windows,Icons,Menus and Pointers also called WIMP.Figure 1.29 shows an example of a GUI with icons and menus on the computer desktop. Windows A window is a part of the screen that holds its own document or message. Most computers now use window-based programs (Fig 1.28). A window can take up the whole screen or can be resized, moved or shrunk (minimised). Each time you open a folder, you see its contents in a new window. More than one window can be open at the same time.is is particularly useful if you want to move from one window to another or to copy les from one window to another. Fig 1.28 An example of two window-based programs (word processor and spreadsheet program) that are open at the same time Icons An icon is a tiny picture of an object that is displayed on screen (Fig 1.29). Normally, you can use the icon in some way. For example, by using the mouse to double click on the icon of the Microsoft Excel spreadsheet program, you will start the program. Fig 1.29 Icons allow you to easily recognise programs in a graphical user interface (GUI)
1.9 User interfaces 33 Icons are designed to make things easier for computer users.Instead of having to remember commands, all you have to do is remember what the icons look like. Icons are not just for programs.ere are icons for folders, the recycle bin (wastebasket), disk drives and printers. Menus An advantage of using menus in Windows or on a Mac is that, for most programs, the rst few menus are always in the same order.ey also carry out the same functions, no matter which program you are using. For example, the le menu is rst and enables you, among other things, to create, save and print a document. Pull-down menus are activated by clicking on the menu item (such as ‘File’) using the left mouse button. e menu pulls down just below the menu item, and you can scroll down through the various items. More complicated pull-down menus can produce additional pull-down or pop-up menus. Pop-up menus (Fig 1.30) are activated by clicking anywhere on the document screen using the right mouse button. Some standard commands and options are available on these menus,including the cut, copy and paste commands. Pointers e most common pointing device is a mouse. As the mouse is moved, a pointer moves around the screen. e pointer is a very important part of a GUI, as it enables you to control the computer and to choose window items, to select text in a document or cells in a spreadsheet, and to create drawings and shapes. Other pointing devices include, graphics tablets, joysticks and digital pens for use with touchscreen devices. Improving interfaces Software companies spend a great deal of time and eort trying to improve the interface so that the computer is easy to use. An important part of this is to design the system software and application programs so that they work exactly the same way each time they are used, and the menus are always in the same place. People use computers for many hours a day.erefore, the screen design and screen colours must be visually pleasing and soothing. However, some colours might be impossible for the visually impaired to see, therefore audio hardware interfaces have become useful. Questions 1 For each of the following, indicate whether it is a hardware interface, software interface, or a combination of both: a display screen on a printer b pressing a code on a keypad to open a door c shouting a command to a device which responds with certain actions. 2 Explain what would cause a menu to confuse a user. 3 State what the following terms mean: a WIMP b GUI. Fig 1.30 A pop-up menu from Microsoft Word
34 1.10 Types of computer systems We need computer systems in almost every aspect of human life: from preparing meals, to maintaining cars and travelling to work or school. For example, a control system uses machines to accept input as instructions to produce output, such as changing the red, amber and green of trac lights or a moving a robot arm to pack eggs. A communication system usually transports data through the network from one point to another. A computer information system is responsible for the collection of data, its processing into information, and the overall management and distribution of this information. Computers and communication devices can therefore manage large amounts of information at a faster rate than manual systems, such as ling, sorting and mailing. Fig 1.31 Information systems are now an essential part of oce work When choosing a computer information system for a particular application, you need to consider: ◆ what hardware is used, such as input, storage and output devices ◆ what software is used, including the choice of custom-written, general-purpose and specialised software ◆ what processing takes place ◆ what human–computer interface is used ◆ which people are involved and what work they do ◆ what data is required. e rst four points were discussed earlier in this chapter. You can now apply this knowledge to decide which systems and applications are appropriate in various computer-related elds based on their input, processing, storage and output needs. Types of computer systems Computer information systems can be chosen to suit dierent users and tasks.ey are also classied by their processing speed, storage and portability. Mainframe is term originally referred to the cabinet containing the CPU or ‘main frame’. Mainframes are very large capacity computers with several CPUs, capable of supporting hundreds or even thousands of users simultaneously.ose such as the IBM zEnterprise mainframe are built with spare components to prevent breakdowns. Data ows between peripherals and communication devices. Users may connect to the mainframe remotely, and only the system administrators will have direct access to the physical computer. Primary and secondary storage are therefore extremely large. Organisations such as banks, airlines, universities and government departments use mainframes – they are very expensive to buy, and need full-time sta for their operations, maintenance and upgrades. Desktop systems Also simply called a computer, a personal computer or desktop system (Fig 1.32) ts on an oce desk. It is easy to buy, upgrade and maintain.Its tasks are for a single user. Memory sizes are increasing but it is not uncommon to nd primary storage sizes of 8 GB (RAM) and hard-disk sizes of 1 TB. Most computers now contain multiple processors (CPUs) working at speeds of 3 GHz.eir main use is for oce and school work, games and entertainment,Internet access and data communication (including email).
1.10 Types of computer systems 35 ey can, however, be linked in a network with more powerful computers. Fig 1.32 A typical personal computer Mobile devices Mobile devices (also called handheld devices) include laptops, notebooks, netbooks, tablets, smartphones, e-readers and games consoles.ey are similar to personal computers but are smaller, lighter and contain batteries so that they are not restricted to being connected to electrical outlets. Questions 1 State the most suitable type of computer for each of the following descriptions of computer systems: a used by secretaries for general oce work b very large capacity computers with several CPUs c consumes very little processing power and may or may not be able to connect to the Internet. Embedded system An embedded system is a dedicated computer system that is designed for one or two specic functions.ese systems are therefore embedded as a part of a complete hardware device called an embedded device.ey consume very little processing power and may or may not be able to connect to the Internet.e main aim is to increase the reliability and performance of the device. Embedded devices can be found in digital watches, printers, washing machines, banking ATM machines and even four-wheel drive vehicles and large installations such as trac lights. Some embedded devices have no user interface, while others may use simple menu systems or touchscreens.
36 1.11 Common computer hardware problems Troubleshooting basic computer problems A number of simple problems can occur when using a computer, but a few checks can be performed to identify the possible cause(s).ese checks can determine whether the problem can be rectied immediately or if there may be a need to seek further technical assistance. Computer, laptop or mobile device does not respond when power is turned on 1 Ensure that the power cable is connected to the power connector on the back of the computer or device and plugged into the electrical outlet. 2 If it is plugged into a power strip or surge suppressor, check that the power strip is connected to an outlet and turned on. 3 Make sure that the electrical outlet is working.is can be done by testing it with another device such as the monitor or a printer. 4 Briey bypass the surge suppressors, power strips and extension cables in turn, which connect the computer directly to the power outlet, to verify that the computer turns on. 5 Try using another power cable that is suitable for the device.If the power turns on, then the cable needs replacing. Printer problems 1 Ensure the printer driver is installed on the computer. 2 Ensure that the printer is plugged into a power strip or outlet and the printer is turned on. 3 Check that paper is not stuck in the printer. Open the printer and remove the component that holds the paper. You may need to remove the ink or toner cartridge to see if paper is stuck under the cartridge. You may see an error message on the monitor or the printer lights may indicate what the error could be. Printer is receiving power but is not printing correctly 1 Ensure the printer contains one or more ink cartridges or that the correct toner is installed. 2 If the print quality is poor, the ink or toner cartridge may need to be replaced. 3 Ensure printer settings for ink cartridge alignment, paper orientation, margins are correctly set. 4 If the print quality is low, check the print quality being used – options are provided to set the quality of print being used from the printer. Draft, Normal and Best are examples of print quality you may see for an inkjet printer. 5 Some printers use Wi-Fi, so check on the display panel to see if the printer’s Wi-Fi is connected. If no paper is seen when you try to print 1 Ensure no parts of the printer are open. 2 Check that paper is correctly placed in the printer. 3 Verify that the correct data cable is being used, and the cable is connected to the computer and the printer. 4 Ensure that you have selected the correct printer. Several printers may be installed, and you must choose the required printer in the print dialogue window (Fig 1.33). Fig 1.33 Check that the correct printer has been selected
1.11 Common computer hardware problems 37 Printout is blank 1 Change the ink or toner cartridge 2 If the problem persists, seek further technical assistance since the nature of the problem may require an experienced technician or a new printer. Monitor problems Blank screen 1 Check the monitor power light – if it is o, then press the button to ensure that the monitor is turned on.If the power light is on, then the monitor has power. Alternatively, if the monitor light is blinking or in a dierent colour, then the monitor may be in power save mode. Press a key on the keyboard or move the mouse. 2 Check the monitor cable connections. Check to ensure that the monitor power cable is connected to an outlet, power strip or surge suppressor. Check the monitor data cable is connected to the computer correctly. 3 Ensure the electrical outlet is working by testing with another device. Screen difcult to read 1 Monitor settings may need to be adjusted (such as colour, contrast or brightness). 2 Ensure that no strong sources of magnetism are near to the monitor – such as speakers and ampliers. 3 Monitors should be kept away from external power sources such as fans and uorescent lamps and radios.ese can cause the screen image to appear to vibrate. Nearby power sources should be turned o to check for interference. 4 Monitors facing bright sources of light such as windows and lights can make the images dicult to see.e monitor should be turned away from strong light sources. Battery problems For laptops and mobile devices, check the amount of charge in the battery. Move the cursor arrow over the battery icon while the laptop is connected to power adapter to view the remaining charge. Figure 1.34 shows some phases of battery use. Fig 1.34 Dierent phases of battery use e battery may need charging or replacing if: ◆ the laptop or mobile device shuts o when the power adapter is unplugged ◆ the device powers o soon after use ◆ the battery icon indicates that a battery is not detected or found. Try another cord of the same make and model.If the battery charges then the power cord may need replacing. Questions 1 You have been watching YouTube videos on your phone for about 45 minutes, then your phone suddenly powers o. Give one possible cause for this problem. 2 You found a printer cartridge still enclosed in its packaging. Since your printer needs ink, you decided to replace your empty cartridge with the one you found. However, the printer still does not print on the paper. Explain why this problem may occur.
38 1 End of chapter exam-style questions Multiple choice questions 1 Which of the following enables a computer to temporarily store instructions and data? a hardware b input devices c memory d peripheral devices. 2 Which of the following controls the hardware and how all other software works? a application software b computer programs c operating system d peripheral devices. Questions 3 to 5 are based on the following devices: i keyboard ii keypad iii touchpad. 3 Which of the devices contains only a block of buttons that contain digits and symbols? a i only b ii only c iii only d i and ii only. 4 Which of the devices is not suitable for the visually impaired? a i only b ii only c iii only d i and ii only. 5 What is the main method to use these devices? a Laser b Light c Sound d Touch. Questions 6 and 7 are based on the following printer types: i dot matrix ii laser iii thermal. 6 Which of the following are non-impact printers? a i only b ii only c i and iii only d ii and iii only. 7 Which printer uses ink that fades over time? a i only b ii only c iii only d i, ii and iii. 8 Each of the following has its screen integrated with the system unit and keyboard except: a personal computer b laptop computer c mobile phone d notebook computer. 9 Which of the following systems relies on precisely positioned marks on a form? a EPOS b MICR c OCR d OMR. 10 Which of the following holds the temporary operating instructions for the computer, its programs and the data? a ALU b CPU c RAM d ROM. 11 The process of starting a computer is known as: a memory management b software control c booting d crashing. 12 The MPEG le format compresses which type of data? a graphics b music c text d video.
1 End of chapter exam-style questions 39 13 Software that is made for use in specic organisations is called: a customised b custom-written c integrated d specialised. 14 The type of interface that allows a user to interact with a computer or device using a touchscreen is: a graphical b hardware c menu-driven d software. Short answer questions 15 Explain the meaning of the term‘IPOS cycle’. 16 Complete the following sentences by using the most appropriate device from the list: a A __________ records voices for presentation software. b A __________ controls multimedia projectors. c A __________ is used to type data for a document. d A __________ reads information from a smart card. e A __________ is used in ight simulators. i remote control ii microchip reader iii joystick iv graphics tablet v keyboard vi microphone. 17 Categorise each of the following examples as either (D) a storage device or (M) storage media: a b c d 18 Circle the most appropriate term in each of the following statements: a When data is retrieved from sequential/direct access storage devices, the device will start from the beginning of the data to be read from, and proceed in a sequence, until it reaches the required data. b An example of a direct/sequential access storage device is a hard disk drive. c Direct/Sequential access storage devices access data immediately without having to read data from the beginning through to where the data is located. 19 Figure 1.35 illustrates an access device. Data is stored at each position on the device. Fig 1.35 a Starting from the rst position at the left and moving to the right, write the letter found in each position. b If the data is accessed from the rst location (C), follow the arrows and write the output in each position. c If the positions were numbered from 1 to 8, what would be the output if the data was accessed in the following order: i 6783 ii 82567. d Circle the appropriate response: There is no order/a specic order to how the data is stored on the device. The diagram is illustrating serial/random access or sequential/direct access to the data. The speed to access data on this device would be fast/slow. A DVD/magnetic tape is most suitable for this type of access.
40 CHAPTER 2 2.1 Data and information INFORMATION PROCESSING Data is raw, unprocessed facts. For example, the numbers 26, 29 and 30 represent data.We do not know what the three numbers represent – they could mean just about anything – such as the temperature in degrees Celsius, the dates of interschool sports events or even the number of students in three classes. Information is processed data.e three numbers can therefore indicate what type of clothing to wear to keep cool based on the temperature, how close the exams are, or how many exam papers to print for each class. Data processing is the manipulation of data to obtain information. So, taking one of the examples above, nding the average of the three numbers gives an indication of how warm the days have been. e term information system is given to any recordkeeping system.We come across information systems all the time. Common examples of manual information systems are dictionaries and telephone directories. What these examples have in common is that data has been collected (input), processed and displayed (output) in order to provide useful information. Information is collected for the purposes of culture, leisure, work, research and everyday life.In organisations, however, it is mainly used for planning and decision making.ere are many sources of information, including, for example: ◆ measurement: sales, productivity output, cash receipts ◆ formal and informal communication: word of mouth, meetings, announcements, interviews ◆ publications: hurricane-preparedness tips, research, daily newspapers, media reports and trends in chronic diseases ◆ questionnaires: opinion polls and market research ◆ products: labels containing ingredients, quantities, contents origin and dosage. e value of information can include the cost of production, the cost of distribution and the value to the purchaser.e more valuable the information is to the customer, the more the organisation can charge for it. Also, customers may be willing to pay more to get information quickly. With the rise of the Internet, two elements in this value chain have changed.e cost of distributing information has been reduced dramatically for web providers. Also, ‘free’ information may have additional value. An online newspaper story may include graphs or pictures and links to other stories on the same topic. Once information is collected, it is often communicated directly to the person who wishes to use it.In order for it to be useful, information must be: ◆ relevant: it must be what the user needs to know, and be up-to-date ◆ accurate: it must be as correct as possible ◆ timely: information should be provided for problem-solving before a critical stage is reached and opportunities are lost ◆ complete: it must represent a ‘whole’ picture of a problem or solution
2.1 Data and information 41 ◆ in an appropriate medium: it should be delivered using an appropriate communication medium, whether by printed material or storage device ◆ cost-eective: the value of information should be more than the cost involved in its collection. Information as a commodity An information commodity is an item of information that can be bought or sold. For example, with online information you may have to pay a charge every time that you access that information. e major types of information for sale are: ◆ databases, especially banking and other nancial information that give demographic, tracking and buying trends Questions 1 Explain what is meant when data is said to be relevant. 2 Name two characteristics of data, other than relevance, that would determine if it is useful. 3 What is the term given to an item of information that can be bought or sold? ◆ information retrieval systems such as abstracting and indexing services ◆ full text databases and reference materials such as encyclopaedias ◆ other, less formal, publications such as subjectspecialised bulletin boards, which in some cases may replace the more traditional journals.
42 2.2 Validation and verification A common problem with manually entering data into a computer system is that it is very easy to input incorrect data. Examples include users mistyping a name or address in a database so that letters are sent to the wrong person. However, it is also possible for a device to misread a barcode and therefore not provide any information to the user. Errors Errors occur in any computer information system. ere are several approaches to dealing with the problems that errors cause, specically preventing errors (so that they do not occur) and detecting when errors do occur (so that they can be corrected). Below a few approaches are considered. Data entry errors Sometimes data cannot be automatically scanned into the system for storage, so a common way is to type the data directly into the computer system. Data entry errors, such as transposition errors, would then occur when an operator enters data using a keyboard and mixes up digits and/or letters. For example, the number 32 may be entered as 23. Other errors occur when data entry requirements are not clear. Do you interpret 07/01/2019 as July 1 2019 or 7 January 2019? ese data entry errors can be either accidental or deliberate. ◆ Accidental errors occur unintentionally: data is entered or a command is issued by mistake, in good faith, but in error. ◆ Deliberate: if errors are made deliberately, then the user probably knows enough to get around any validation checks. Examples include a disgruntled employee entering ctitious data into a company’s database. Possible solutions to this problem include le access permissions imposed by the operating system, better vigilance of the administrator and the cross-referencing of data with other supposedly reliable sources. Software and hardware errors ere are two types of error here. Software might malfunction, erasing or corrupting previously entered data. Hardware may develop a fault (often intermittent) that corrupts data. Examples include bad sectors on a hard disk, bad memory or a power surge. e application may appear to accept data correctly but when that data is retrieved it is corrupt. Transmission errors Transmission errors occur when data received is not the same as that transmitted by the sender (Fig 2.1). Fig 2.1 Illustration of transmission errors Validation Data validation is the computerised checking of input data for errors (data that may be unreasonable or incomplete) before it is processed.It does not conrm the accuracy of data.ere are dierent methods of validation.e most appropriate method(s) to use will depend upon what data is being entered. Range check Range check ensures that the data entered is within a certain range. For example, when you enter a number corresponding to a month of the year, the range of acceptable numbers is 1 to 12. Reasonableness check is check tests whether the data obeys specied criteria. For example, the age of a child at preschool could be about 4 years old, but not 14 years.Reasonableness checks are therefore used to detect doubtful data. Data type check is is also known as a character or alphanumeric check.When a database is created, each eld will
, Fail Consistency check A consistency check compares the contents of two or more elds to make sure that they make sense.It is also called an inconsistency check, since it mostly identies errors and discrepancies in the data.is check compares new data with previously entered data. For example, checking that the age entered corresponds to the age calculation from the date of birth. Consider the following employee record: Employment Status Form Are you unemployed? No Unemployment benefits claimed? Yes Number of years working 12 Current occupation Foreman It would be useful to have a consistency check to crosscheck the information in the ‘Are you unemployed?’ and ‘Unemployment benets claimed?’ elds, since you should not claim for unemployment benets if you are still working.In this example, therefore, either an error has been made on input or this is a deliberate attempt to claim benets while still working. Other examples of consistency checks are: ◆ Single mothers with children can claim for childcare allowance. Check that the number of children is not zero. ◆ Only full-time employees are paid overtime. Check that these elds correspond. Presence check is type of check ensures that the data is actually entered.It can be used on any eld in a database. For example, every person in a particular database must be assigned to a department.erefore, a presence check on each employee’s record could ensure that a department is entered in the form. Format check is check veries that the data has been entered in the correct format. For example, a national ID number may have the format 999-9999-X999, where 9 represents a number and X represents an alphabetic character. Length check is check veries that the data entered is the correct length. For example, a password for a credit card may be four digits long, therefore entering three or ve digits may result in an error. Check digit A check digit is an extra digit added to the end of a code.It is used to detect errors arising from transcription and also to ensure that codes originally produced by a computer are re-entered into another computer correctly.It is calculated from the other
2 Information processing 44 digits in the number. Check digits are included in barcode numbers. Fig 2.2 A barcode showing a check digit Verication Data verication is the checking for mistakes such as transcription errors when data is copied from one medium or device to another. Verication checks do not guarantee that the entered data is correct, it only checks that the data entered matches the source data.erefore, you should be aware that if the original form was completed incorrectly, then the entered data may pass some verication checks despite being incorrect. One way to guarantee that the data entered matches the source data is a procedure called double (data) entry. Data is entered twice using a program that checks each second entry against the rst. For example, some applications require users to enter their password twice.e application compares the two passwords to conrm that they are the same.In other applications where there is more data to be entered, the program produces a list with the pairs of data that do not match so that the correct values can be re-entered. Visual checks Another verication method is to use on-screen prompts. After a set of data is entered, it is redisplayed on the screen.e user is prompted to read it and conrm that it has been entered correctly.If the user has entered any data incorrectly, it is re-entered. is method of verication is not very reliable since many data entry personnel will not read the information that is redisplayed or check it carefully against the source document. Accidental errors can also be prevented by verication in asking for conrmation of instructions. For example, if you try to delete les the computer may ask ‘Are you sure [y/n]?’ or it may display a summary of input data and ask for verication of its validity before the data is stored. Interpretation of coded data Before the responses to questionnaires can be analysed, they must be edited and coded before the data entry process.e person coding these responses should have no doubt as to what should be entered.is may sound simple, but consider the following case (Fig 2.3). Fig 2.3 Coding involves assigning a label to each question Coding involves assigning a label to each response,such as 1 for ‘yes’ and 2 for ‘no’. Sometimes, people will write in a response such as ‘can’t remember’ or ‘unsure’, and you must decide what to do.It could either be ignored, or a new code and value could be added to the question. As another example, consider a library database where books are classied as being Fiction, Non-ction or Reference.is information could be stored as text in a database where the corresponding eld length would be 11 to store the longest classication, ‘Non-ction’. Alternatively, the classications could be coded like this: Classication Code Fiction F Non-fiction N Reference R Coding information reduces the amount of storage space required and speeds up the process of typing the information in. For coding to work properly everyone needs to know what the correct codes are. Problems associated with shared data In organisations, information is constantly sent and received among various departments.Traditionally, if two people need to use the same le, the rst person
2.2 Validation and verication 45 who found the le (in the ling cabinet!) made use of it; the other person waited until the rst returned the le to the drawer. Computers and networks mean not only that neither person has to search through a drawer to locate the le, but also that both persons may access the data le at the same time. At least, it may appear in that way.Is this a good way to access data les? Let us suppose that two teachers were both accessing a data record for the student Amerra Taitt (Fig 2.4). One teacher wishes to adjust the mark received in IT from the original 69% to 96%.e second teacher wishes to adjust the mark received in Geography from 18% to 81% (typo errors in both subjects!).What happens when the records are saved to the main database? Will both changes be accepted? Data-sharing in this manner can lead to problems of data accuracy when the data records are saved.e teacher who saves the changes rst will have the marks overwritten by the teacher who saves the changes last, which of course will erase the changes made by the rst teacher. How can this problem be avoided? Good databases avoid this problem by allowing only one user or system to access a data record at a time. When an attempt is made by a second person to access the same record, a message may be provided (Fig 2.5). Computer systems that provide shared access to data must have security features in place.is prevents users from gaining access to data which they are not authorised to view or modify.e users of the computer system should be provided with their own usernames and passwords for the login process. ere are also access privileges depending on the user’s level. For example, a student at the school will be allowed access to certain software such as word processing, perhaps email facilities and limited Internet access. A clerk will have access to student records, personnel records, Internet access, email, and payroll programs.e network administrator will have the highest level of access, including data records of usernames and passwords and the network administration and security software. Fig 2.4 What happens if two people want to change data at the same time? Fig 2.5 A well-structured database will prevent simultaneous access to the same database record Questions 1 Explain the dierence between data validation and data verication. 2 Give an example of a data-related hardware error. 3 Copy and complete the table below by giving an example of valid data for each item: Field name Acceptable values Example of valid data a Opening hours 8 am to 4pm b Bulk orders >250 c Standard shipping 3 to 5 days d Centre number 999999 where 9 represents a digit
46 Automated methods of data capture Many of the output devices discussed in Chapter 1 are human-readable, meaning that a hard copy of the output is printed as reports, graphs, charts and so on. Other devices are machine-readable, meaning that the output is in a form that only a computer can process. An example is output to a monitor.is is called softcopy output since it is not printed on paper or other physical material. Data-capture forms ese forms must be designed so that their instructions are clear and concise, leaving no doubt as to how to enter the data onto the form. For example, the format for dates could be specied as ‘dd/mm/yyyy’ so that the format ‘mm/dd/yy’ is not used in error. e responses from the forms are called humanreadable since data entry personnel manually enter the responses written on the forms.is method of data capture is liable to transcription and other errors when the data is entered into the computer. One method of avoiding transcription errors is double (data) entry, where the data is entered twice by two dierent people and the computer will only accept the data if the two versions are identical. Turnaround document A turnaround document is a machine-readable document that has some information printed on it by a computer but has more information added to it by a human.It is then fed back into a computer to transfer this newly added information.ese documents serve two purposes.ey are used to: ◆ verify the accuracy and completeness of information that has already been entered ◆ update information already entered with additional data. Optical mark recognition and optical character recognition are often used together in a turnaround document. Figure 2.6 shows an example of a turnaround document used to record the reading on an electricity meter. Fig 2.6 The meter reader has marked the reading as 7618 on this turnaround document Another example of a turnaround document is the multiple-choice sheets used in examinations. Information such as the candidate number, subject and school code is printed on the multiple-choice answer sheet by the computer.e student takes the test and lls in the answer grid by making marks in the appropriate boxes using a pencil or ballpoint pen.e form is then returned to the examination council to be fed into a special reader. Fig 2.7 Multiple-choice exam sheet 2.3
2.3 Automated methods of data capture 47 Optical character recognition (OCR) is used to read the student’s pre-printed information from the form, whereas optical mark recognition (OMR) is used to read the answers that have been added. All the information can be read into the computer automatically.e sheet is marked, and the total mark is printed without any need for human intervention. Turnaround documents allow cheap, fast input of information into a computer system. Data can also be printed on turnaround documents in barcode format. Alternatives to turnaround documents In some industries, turnaround documents are being replaced by small handheld computers, including mobile devices.ese pocket-sized devices have a display screen and touchscreen keyboard. For example, many local utility companies now issue their meter readers with handheld computers. At the start of the day the names and addresses of the customers to be visited are downloaded into the computer. As the meter reader visits customers’ homes, he or she types the meter readings into the computer. At the end of the day the readings can be transferred automatically onto the main computer to issue bills. Another example involves courier services that equip drivers with these devices. As the courier delivers a package, the recipient uses a stylus to sign the delivery document on the device.is signature is captured digitally and uploaded to the database as proof of delivery. Fig 2.8 Turnaround documents are being replaced by small handheld computers Data logging Computers are often used by companies and scientists to automatically measure and record changes in conditions such as the temperature, the speed at which a ball is travelling in sports such as cricket and baseball, the amount of light or oxygen in a room or even the level of noise being made by vehicular trac near a hospital. Data logging is a method of automatic data capture where a reading from a sensor is input at regular intervals.is data can then be processed to provide analysis of the environment (Fig 2.9). Fig 2.9 This student is checking water quality using a sensor connected to a data logger. This data can then be processed to provide analysis of chemicals in the water
2 Information processing 48 A data logging system consists of sensors connected via an interface to a computer and some data logging software (Fig 2.10).e sensors will take measurements and at required intervals the software will record the data.e results can then be displayed as a graph or a table. Microlm Microlm is often used as an alternative to the printer. e output is ‘printed’ on a roll of lm (computer output microlm) or sheet of lm (computer output microche) rather than paper.In addition to being faster, this method also condenses large stacks of paper Questions 1 State which of the following output is hard-copy output or soft-copy output: a human-readable b machine-readable. 2 Give an example of a document that is machinereadable. into small amounts of microlm or microche with no special programming.e drawback of computer output microlm or microche (COM) is that it takes a special device to print the microlm and a special viewer to read it. INTERFACE Temperature sensor Light sensor Input connections Output connections Computer Fig 2.10 Components of a data logging system