Cambridge igcse computer science workbook pdf free pdf s

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Cambridge igcse computer science workbook pdf free pdf s

No Text Content! CambridgeNotUfnocr?orSMraalercestheadllPCraovofesndish IGCSETM Computer Science Kay Summers WORKBOOKCambridge IGCSETM Computer Science Sarah Lawrey WORKBOOK NotUfnocr?orSMraalercestheadllPCraovofesndishNotUfnocr?orSMraalercestheadllPCraovofesndish? 2021 Marshall Cavendish Education Pte Ltd Published by Marshall Cavendish Education Times Centre, 1 New Industrial Road, Singapore 536196 Customer Service Hotline: (65) 6213 9688 E-mail: [email protected] Website: First published 2021 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the copyright owner. Any requests for permission should be addressed to the Publisher. Marshall Cavendish is a registered trademark of Times Publishing Limited. ISBN 978981-4941-60-0 Questions and answers in this book have been written by the authors. Printed in Singapore iiiHow to use this book NotUfnocr?orSMraalercestheadllPCraovofesndishFor further learner support, alongside the Student's Book,Chapter 3 the Workbook offers a range of exercises to reinforce and consolidate key terms and concepts learnt from each chapter. Exercise 1 Embedded systems This Workbook is part of the Marshall Cavendish Education 1 What is the main purpose of the CPU? suite of resources that will support you as you follow the 0478/0984 syllabuses and prepare for the Cambridge IGCSE 2 What is a microprocessor? Computer Science exam. 3 A washing machine is an example of an embedded system. List four more embedded systems. Formative Exercises These exercises are meant to evaluate how well you 4 A personal computer (PC) is one example of a general purpose computer. List two other examples. are learning each section in a chapter. They are intended to help build your subject literacy A panroWdcEhtehxesesreencraaelrcxleeeiddscuaethttaee2safinet.tdcThihn-esdtCeruPccoUtdiuoesn-eFessxesesteotcvucreethdera-cilmdydcmieflefeecirdseoipnadtteercelfoyo-mrbmeepxfeoodenreebcntyuhttsehtyteeoaCrdcePoyUfet.chtTclihshe.iesdcyinclteoftehtechCePsUa?n instruction into the CPU, decodes and boost your confidence in understanding and it, answering questions. The exam-style questions also help you to be familiar 1 with the format of the questions in the exam. 2 What is the purpose of a register? 28 Hardware Chapter 1 IGCSE_CS_WB_Ch 3.indd 28 can be used to reduce the size of a text file. 3 The paragraph below explains how lossless compression the size of the file. The algorithm looks for 26/01/21 9:53 PM file and them. Each index Revision checklist Fill in the missing words. with the position where it This exercise is included at the end A compression algorithm is used to patterns in the text occurs in the text. of each chapter to help you identify knowledge gaps. It is designed for along you to pause and reflect on your learning experience by evaluating your is stored in a understanding of the concepts taught. Revision checklist Need to revisit Satisfactory Confident iv IfIoIudIumcrIneIuamnaIcaduneIndbndcaIncscentaIddatinueIhhdnaicrhrudoInneiIrunsyiontaoaaIuensnefItruccicndrptroddunsaanrddufaluanoaeytduoesnnenvndndceanasnofdtmrdreierddfdaettnrnesdmfdtefecrearsiontewprdntsdethchtrtaarsetatrrdswargrtlaboeonthsmashetgctssnattaexiwonetdetsuotoeaapndohaanthst'daslwnrndshodwnfiaderdaseho,ecdlethtsodnegoiehcnoeahopeitnnowctdtgiohenowhefmrivchatimwvfenimnedhweowlecraeseuspacyneecwaanepaeawhd,npeld8ttlmfnedolnfbyhsifp,dubhiafnmedslbtiaiopowettcrylinaigcwennapitdolwefottatishhesadvioAhsntsmfirbothyerzheatyrshyStoyhnioeaxyrepenaCidtaveeaatrssooauaeaonerIcedxhIchcerftgrofadncreyiaaeoosfafaeedaomlanctnormmsohinpnsnermidodilmwepyosurdctpuipnemxepusnUtimaasrumsainaageutaonelneattdnemeeesthiaendngipbsreedseacrlrepteesocrrsioadpuanrwelupdisnpredfseonmapfeiiroehdpootlesduereprridsaiyyvserredstcirepliaietisdsettiaovnsintonoieovsasev8elguonoldeseteunraibamcntubetltaatosbicibtpirsicvnnobtssuitseoedrnsasednobeeranomyearxsbrusinyneunprteaiisn,pynfnenaitanynipmdrhcgarinsddetbnoyirtaadaf,saeitysiltniislgeloilnnmiettlivageohsitc,veress,enuleyeulgr8esudei-snbsisrnegitgof 16 Computer systems 28/01/21 9:26 AM IGCSE_CS_WB_Ch 1.indd 16Contents NotUfnocr?orSMraalercestheadllPCraovofesndishChapter 1 Computer systems Chapter 7 Algorithm design and problem solving 1.1 Number systems 1 1.2 Text, sound and images 12 7.1 Algorithm design and problem 1.3 Data storage and compression 15 solving66 Chapter 2 Data transmission Chapter 8 Programming 2.1 Types and methods of data 8.1 Programming concepts 91 transmission 17 8.2 Arrays 107 8.3 File handling 111 2.2 Methods of error detection 23 2.3 Encryption 25 Chapter 9 Databases Chapter 3 Hardware 9.1 Databases 115 3.1 Computer architecture 27 Chapter 10 Boolean logic 3.2 Input and output devices 32 3.3 Data storage 34 10.1 Boolean logic 123 3.4 Network hardware 38 Chapter 4 Software 4.1 Types of software and interrupts 42 4.2 Types of programming language, translators and integrated development environments (IDEs) 46 Chapter 5 The internet and its uses 5.1 The internet and the world 50 wide web 53 53 5.2 Digital currency 5.3 Cyber security Chapter 6 Automated and emerging technologies 6.1 Automated systems 58 6.2 Robotics 61 6.3 Artificial intelligence 63 vNoUt fno?croMSrraaelrecstheadllPCraovoefsndishCHAPTER 1 Computer systems NotUfnocr?orSMraalercestheadllPCraovofesndish At the end of this chapter, you will be able to: ? Understand how and why computers use binary to represent all forms of data ? Understand the denary, binary and hexadecimal number systems ? Convert between positive denary and positive binary, positive denary and hexadecimal, and hexadecimal and positive binary ? Understand how and why hexadecimal is used as a beneficial method of data representation ? Add two positive 8-bit binary integers ? Understand the concept of overflow and why it occurs in binary addition ? Perform a logical binary shift on a positive 8-bit binary integer and understand the effect this has on the positive binary integer ? Use two's complement to represent positive and negative 8-bit binary integers ? Understand how and why a computer represents text and the use of character sets, including ASCII and Unicode ? Understand how and why a computer represents sound, including the effects of the sample rate and sample resolution ? Understand how and why a computer represents an image, including the effects of the resolution and colour depth ? Understand how data storage is measured ? Calculate the file size of an image file and a sound file, using information given ? Understand the purpose of and need for data compression ? Understand how files are compressed using lossy and lossless compression methods 1.1 Number systems A number system is a method for representing values based on a particular set of units. There are three number systems that you will use here: denary, binary and hexadecimal. Exercise 1 Denary, binary, and hexadecimal 1 Is denary a base-2, base-10 or base-16 number system? Circle the correct answer. Base-2 Base-10 Base-16 2 Is binary a base-2, base-10 or base-16 number system? Circle the correct answer. Base-2 Base-10 Base-16 Computer systems 1Chapter 1 3 Is hexadecimal a base-2, base-10 or base-16 number system? Circle the correct answer. Base-2 Base-10 Base-16 NotUfnocr?orSMraalercestheadllPCraovofesndishExercise 2Converting denary values Denary values can be converted to binary values and vice-versa. 1 Convert the denary value 7 to a 4-bit binary value. Denary 4-bit binary 7 Working space 2 Convert the denary value 10 to a 4-bit binary value. 4-bit binary Denary 10 Working space 3 Convert the 4-bit binary value 0011 to denary. Denary 4-bit binary 0011 Working space 4 Convert the 4-bit binary value 1001 to denary. Denary 4-bit binary 1001 2 Computer systemsChapter 1 Working space NotUfnocr?orSMraalercestheadllPCraovofesndish5 Convert the denary value 24 to an 8-bit binary value.8-bit binary Denary 24 Working space 6 Convert the denary value 101 to an 8-bit binary value. 8-bit binary Denary 101 Working space 7 Convert the denary value 200 to an 8-bit binary value. Denary 8-bit binary 200 Working space 8 Convert the 8-bit binary value 00011011 to denary. Denary 8-bit binary 00011011 Working space Computer systems 3Chapter 1 Denary 9 Convert the 8-bit binary value 10011111 to denary. 8-bit binary 10011111 Working space NotUfnocr?orSMraalercestheadllPCraovofesndish 10 Convert the denary value 555 to a 12-bit binary value. Denary 12-bit binary 555 Working space 11 Convert the denary value 2001 to a 12-bit binary value Denary 12-bit binary 2001 Working space 12 Convert the 12-bit binary value 100110011001 to denary. Denary 12-bit binary 100110011001 Working space 4 Computer systemsChapter 1 13 Convert the denary value 1056 to a 16-bit binary value. Denary 16-bit binary 1056 Working space NotUfnocr?orSMraalercestheadllPCraovofesndish 14 Convert the denary value 5000 to a 16-bit binary value. Denary 16-bit binary 5000 Working space 15 Convert the 16-bit binary value 0011010111001100 to denary. 16-bit binary Denary 0001010111001100 Working space Exercise 3 Converting hexadecimal values Denary and binary values can also be converted to hexadecimal, and vice-versa. 1 Convert the 4-bit binary value 0011 to hexadecimal. 4-bit binary Hexadecimal 0011 Working space Computer systems 5Chapter 1 Hexadecimal 2 Convert the 4-bit binary value 1001 to hexadecimal. 4-bit binary 1001 Working space NotUfnocr?orSMraalercestheadllPCraovofesndish 3 Convert the 4-bit binary value 1110 to hexadecimal. Hexadecimal 4-bit binary 1110 Working space 4 Convert the hexadecimal value 4 to 4-bit binary. 4-bit binary Hexadecimal 4 Working space 5 Convert the hexadecimal value A to 4-bit binary. 4-bit binary Hexadecimal A Working space 6 Computer systemsChapter 1 6 Convert the hexadecimal value F to 4-bit binary. 4-bit binary Hexadecimal F Working space NotUfnocr?orSMraalercestheadllPCraovofesndish 7 Convert the 8-bit binary value 00001000 to hexadecimal. 8-bit binary Hexadecimal 00001000 Working space 8 Convert the 8-bit binary value 10110001 to hexadecimal. 8-bit binary Hexadecimal 10110001 Working space 9 Convert the 8-bit binary value 11000000 to hexadecimal. 8-bit binary Hexadecimal 11000000 Working space Computer systems 7Chapter 1 8-bit binary 10 Convert the hexadecimal value 4B to 8-bit binary. Hexadecimal 4B Working space NotUfnocr?orSMraalercestheadllPCraovofesndish 11 Convert the hexadecimal value CD to 8-bit binary. 8-bit binary Hexadecimal CD Working space 12 Convert the hexadecimal value 3B0 to 12-bit binary. 12-bit binary Hexadecimal 3B0 Working space 13 Convert the denary value 103 to hexadecimal. Hexadecimal Denary 103 Working space 8 Computer systemsChapter 1 14 Convert the hexadecimal value A3 to denary. Denary Hexadecimal A3 Working space NotUfnocr?orSMraalercestheadllPCraovofesndish 15 Convert the hexadecimal value 2E to denary. Denary Hexadecimal 2E Working space 16 Convert the 12-bit binary value 110100001111 to hexadecimal. 12-bit binary Hexadecimal 110100001111 Working space 17 Convert the hexadecimal value 04C to 12-bit binary. 12-bit binary Hexadecimal 04C Working space Computer systems 9Chapter 1 Exercise 4 Adding binary values Binary values can be added together. Make sure that you show your working when adding the binary values. NotUfnocr?orSMraalercestheadllPCraovofesndish1 Add the 4-bit binary values 0001 and 0110.2 Add the 4-bit binary values 0101 and 0010. 0 0 0 1 0 1 0 1 + 0110 + 001 0 3 Add the 8-bit binary values 00101000 and 01100011. 4 Add the 8-bit binary values 10101010 and 01110111. 0 0 1 0 1 000 1 0101 010 + 0 1 1 0 0 011 + 0 1 1 1 0 1 11 5 Name the error caused by this binary addition. 6 Why does this type of error happen? Exercise 5 Logical shifts Logical shifts can be performed on the binary contents of a register. 1 Perform a logical binary shift one place to the left on this binary value. 01001111 What effect did the logical shift have on the binary value? 10 Computer systems2 Perform a logical binary shift two places to the right on this binary value. 1 Chapter 1 00110 00 NotUfnocr?orSMraalercestheadllPCraovofesndish What effect did the logical shift have on the binary value? Exercise 6 Two's complement Two's complement is another method of representing binary values. It is often used to represent negative binary values. 1 Convert the denary number 47 to two's complement 8-bit binary. Denary Two's complement 8-bit binary 47 Working space 2 Convert the denary number -75 to two's complement 8-bit binary. Denary Two's complement 8-bit binary -75 Working space Computer systems 11Chapter 1 3 Convert the two's complement 8-bit binary value 01010110 to denary. Two's complement 8-bit binary Denary 01010110 Working space NotUfnocr?orSMraalercestheadllPCraovofesndish 4 Convert the two's complement 8-bit binary value 10001011 to denary. Two's complement 8-bit binary Denary 10001011 Working space 5 What is the largest number that can be stored in 8 bits using two's complement? 6 What is the smallest number that can be stored in 8 bits using two's complement? 1.2 Text, sound and images In computing, text, sound and images are all converted to binary then processed by the computer. Various methods are used to obtain these binary values. Exercise 1 Character sets When converting text to binary, a character set is used. 1 What is a character set? 12 Computer systems2 Tick () to show whether each statement is true or false. Chapter 1 Statement True False Both Unicode and ASCII are examples of a character set () () Unicode requires more bits per character ASCII can represent a greater range of symbols and emojis Unicode can represent a greater range of different languages NotUfnocr?orSMraalercestheadllPCraovofesndish Exercise 2 Sound waves When converting sound to binary, sound waves are sampled. 1 What is the difference between the sample rate and the sample resolution? 2 How can you increase the accuracy of a sound file to make it sound more like the original? 3 A 10 second sound clip has a sample rate of 1000Hz and a sample resolution of 8 bits. Calculate the file size of the sound clip in kibibytes (KiB). Remember to show all your working. Answer: KiB Computer systems 13Chapter 1 Exercise 3 Converting images to binary When converting an image to binary, the resolution and colour depth are set. 1 Draw a line from each term to its correct definition. NotUfnocr?orSMraalercestheadllPCraovofesndish Colour depth The number of pixels in an image Resolution The number of bits used to represent each colour in an image Pixels The small squares of colour that make up an image 2 What will be the effect on an image if the colour depth is reduced? 3 A student has five images. Each image has a resolution of 1000 pixels wide by 800 pixels high. Each image has a colour depth of 16 bits. Calculate the file size needed to store the images in mebibytes (MiB). Remember to show all your working. Answer: MiB 14 Computer systemsChapter 1 1.3 Data storage and compression Several data storage units can be used to identify the size of a file. NotUfnocr?orSMraalercestheadllPCraovofesndishExercise 1Data storage units 1 Number the data storage units from 1 (smallest) to 9 (largest). The first one has been done for you. Data storage unit Number Byte 1 Kibibyte (KiB) Gibibyte (GiB) Nibble Exbibyte (EiB) Mebibyte (MiB) Tebibyte (TiB) Bit Pebibyte (PiB) Exercise 2 File compression Sometimes, files are compressed before they are stored. There are two methods of compression: lossy and lossless. 1 Tick () to show whether each statement is true or false. Statement True False () () Compression reduces the size of the file A compressed file will be transmitted slower A compressed file uses less bandwidth when transmitted A compressed file will take up less storage space 2 A student has several large images to send to a friend. They use lossy compression to reduce the size of the images before sending them. List two ways that lossy compression will reduce the size of the images. Computer systems 15Chapter 1 3 The paragraph below explains how lossless compression can be used to reduce the size of a text file. Fill in the missing words. A compression algorithm is used to the size of the file. The algorithm looks for NotUfnocr?orSMraalercestheadllPCraovofesndish patterns in the text file and them. Each index is stored in a along with the position where it occurs in the text. Revision checklist Need to revisit Satisfactory Confident I understand how and why computers use binary to represent all forms of data I understand the denary, binary and hexadecimal number systems I can convert between positive denary and positive binary, positive denary and hexadecimal, and hexadecimal and positive binary I understand how and why hexadecimal is used as a beneficial method of data representation I can add two positive 8-bit binary integers I understand the concept of overflow and why it occurs in binary addition I can perform a logical binary shift on a positive 8-bit binary integer and understand the effect this has on the positive binary integer I can use two's complement to represent positive and negative 8-bit binary integers I understand how and why a computer represents text and the use of character sets, including ASCII and Unicode I understand how and why a computer represents sound, including the effects of the sample rate and sample resolution I understand how and why a computer represents an image, including the effects of the resolution and colour depth I understand how data storage is measured I can calculate the file size of an image file and a sound file, using information given I understand the purpose of and need for data compression I understand how files are compressed using lossy and lossless compression methods 16 Computer systemsCHAPTER 2 Data transmission NotUfnocr?orSMraalercestheadllPCraovofesndish At the end of this chapter, you will be able to: ? Understand that data are broken down into packets to be transmitted ? Describe the structure of a packet ? Describe the process of packet switching ? Describe how data is transmitted from one device to another using different methods of data transmission ? Explain the suitability of each method of data transmission, for a given scenario ? Understand the universal serial bus (USB) interface and explain how it is used to transmit data ? Methods of error detection ? Understand the need to check for errors after data transmission and how these errors can occur ? Describe the processes involved in each of the following error detection methods for detecting errors in data after transmission: parity check (odd and even), checksum and echo check ? Describe how a check digit is used to detect errors in data entry and identify examples of when a check digit is used, including ISBN numbers and bar codes ? Describe how an automatic repeat request (ARQ) can be used to establish that data is received without error ? Understand the need for and purpose of encryption when transmitting data ? Understand how data is encrypted using symmetric and asymmetric encryption 2.1 Types and methods of data transmission Exercise 1 Data packets A document is too large a section of data to be transmitted from one device to another. There is no infrastructure capacity to transmit such a large amount of data at once. Therefore, it needs to be broken down into packets, which are a much smaller unit of data. 1 Name the three different sections in the structure of a data packet. 2 In which section of the data packet would you normally find the destination address? Data transmission 17NotUfnocr?orSMraalercestheadllPCraovofesndishChapter 2 3 What kind of address is the destination address normally? 4 In which section of the data packet would you find the main content of the data being sent? 5 In which section of the data packet would you normally find the packet number? 6 What kind of data might you find in the trailer of a data packet? 7 In packet switching, does each packet take the same route or can they take a different route? Circle the answer. Same routeDifferent route 8 In packet switching, the data packets will always arrive in order. Tick () to show whether this statement is true or false. Tick () True False 9 What is the name of the network device that chooses the route a data packet will take? 10 In packet switching, when are the data packets reordered after transmission? 18 Data transmissionChapter 2 11 Draw a diagram to represent how data is transmitted across a network using packet switching. Your diagram should include a minimum of two devices and four routers. NotUfnocr?orSMraalercestheadllPCraovofesndish Data transmission 19Chapter 2 Exercise 2 Data transmission Data is transmitted from one device to another using the serial or parallel method. 1 Tick () to show which method transmits data one bit at a time. NotUfnocr?orSMraalercestheadllPCraovofesndish Number of wires Tick () Single wire Multiple wires 2 Tick () to show how many wires are used in parallel data transmission. Data transmission method Tick () Serial Parallel 3 Describe the benefit of using parallel data transmission, instead of serial data transmission. 4 List two benefits of using serial data transmission, instead of parallel data transmission. Exercise 3 Transmission methods Data is also transmitted from one device to another using the simplex, half-duplex or full-duplex methods. 1 Does simplex data transmission happen in one direction only or in both directions? Circle the answer. One direction onlyBoth directions 2 Can you think of two applications where simple data transmission would be suitable? 20 Data transmissionChapter 2 3 Draw a diagram to show how data is transmitted using half-duplex data transmission. NotUfnocr?orSMraalercestheadllPCraovofesndish4 Can you describe how data is sent using full-duplex data transmission? 5 A website designer has a web server beside their desk. They need to be able to send data to and receive data from the web server at the same time, and may also need to make quick changes to the data on the web server, so data transmission to the web server is time critical. Which data transmission methods should be used to send data from the website designer's computer to the web server? Why? 6 An office manager creates a back-up of the data stored on her computer at the end of each day. The file server that stores the back-up is located in a building 1 km from her office. It is very important the data is stored without error on the file server. She only needs to send data to the back-up, and does not receive data from the file server. Which data transmission methods should be used to send data from the office manager's computer to the file server? Why? Data transmission 21Chapter 2 NotUfnocr?orSMraalercestheadllPCraovofesndishExercise 4USB Interface An interface called USB can be used to connect one device to another. 1 Tick () to show which type of data transmission is used in a USB connection. Data transmission method Tick () Serial Parallel 2 List three benefits of using a USB interface to connect a mobile phone to a computer. 3 What are two drawbacks of connecting a server to a computer using a USB interface? 22 Data transmissionChapter 2 2.2 Methods of error detection When data is transmitted from one device to another, there is a chance that errors can occur in the data. This could be because packets of data go missing, or because of interference during transmission. Therefore, several error detection methods can be used to find any errors. NotUfnocr?orSMraalercestheadllPCraovofesndish Exercise 1 Error dectection 1 Which error detection method adds an 8th bit to 7 bits of data, to make each byte meet an odd or even check? Circle the answer. Parity checkChecksumEcho check 2 In which error detection method does the receiver send data back to the sender, to compare the two versions of the data? Circle the answer. Parity checkChecksumEcho check 3 Which error detection method uses an algorithm to calculate a value from the data?This value is transmitted with the data to the receiver. Circle the answer. Parity checkChecksumEcho check 4 The following four bytes of data have been transmitted from one computer to another. Each byte was transmitted using an even parity check. All the bytes have arrived correctly. Write the parity bit that was added to each byte for it to be correct for an even parity check. Parity bit Byte 1011011 0111000 1010110 0000111 5 Can you think of a reason why an error that has occurred in the transmission of data from one device to another is not detected by a parity check? Errors can also occur when data is entered into a device. The data entry could be manual (being typed into a device), or automatic, (such as scanning a barcode). Therefore, there is also an error detection method for data entry, which is called a check digit. Data transmission 23Chapter 2 Exercise 2 Check digit 1 How is a check digit used to detect errors in data entry? NotUfnocr?orSMraalercestheadllPCraovofesndishExercise 3Automatic repeat request Sometimes errors are found in data after transmission. So, systems need a way to request that the data is resent. One method for this is an automatic repeat request (ARQ). 1 During an ARQ process, data is transferred from the sending device to the receiving device. The sending device then starts a timer. The receiving device checks the data for errors, using one of the error detection methods you have studied. What happens next in the ARQ process? 24 Data transmissionChapter 2 2.3Encryption Data is very valuable and we should always make sure that it is stored and transmitted in a secure way. Encryption is one way that data can be kept secure. NotUfnocr?orSMraalercestheadllPCraovofesndish Exercise 1 Encryption 1 What is the name given to the data before encryption? 2 Name the encryption algorithm that is used to encrypt the data. 3 What is the name given to the data after encryption? 4 Tick () to show whether same key or different keys are used to encrypt and decrypt data in symmetric encryption. Keys used Tick () Same key Different key The paragraph below explains how asymmetric encryption is used to encrypt data. Fill in the missing words. The text is encrypted into text using a key. The encrypted data is transmitted to the receiving device. The text is decrypted using a key. 5 Which encryption method is more secure? Why? Data transmission 25Chapter 2 Revision checklist Need to revisit Satisfactory Confident NotUfnocr?orSMraalercestheadllPCraovofesndish I understand that data are broken down into packets to be transmitted I can describe the structure of a packet I can describe the process of packet switching I can describe how data is transmitted from one device to another using different methods of data transmission I can explain the suitability of each method of data transmission, for a given scenario I understand the universal serial bus (USB) interface and explain how it is used to transmit data Methods of error detection I understand the need to check for errors after data transmission and how these errors can occur I can describe the processes involved in each of the following error detection methods for detecting errors in data after transmission: parity check (odd and even), checksum and echo check I can describe how a check digit is used to detect errors in data entry and identify examples of when a check digit is used, including ISBN numbers and bar codes I can describe how an automatic repeat request (ARQ) can be used to establish that data is received without error I understand the need for and purpose of encryption when transmitting data I understand how data is encrypted using symmetric and asymmetric encryption 26 Data transmissionCHAPTER 3 Hardware NotUfnocr?orSMraalercestheadllPCraovofesndish At the end of this chapter, you will be able to: ? Understand the role of the central processing unit (CPU) in a computer ? Understand what is meant by a microprocessor ? Understand the purpose of the components in a CPU, in a computer that has a Von Neumann architecture ? Describe the process of the fetch-decode-execute cycle including the role of each component in the process ? Understand what is meant by a core, cache and clock in a CPU and explain how they can affect the performance of a CPU ? Understand the purpose and use of an instruction set for a CPU ? Describe the purpose and characteristics of an embedded system and identify devices in which they are commonly used ? Input and output devices ? Understand what is meant by an input device and why it is required ? Understand what is meant by an output device and why it is required ? Understand what is meant by a sensor and the purposes of sensors ? Identify the type of data captured by each sensor and understand when each sensor would be used, including selecting the most suitable sensor for a given context ? Understand what is meant by primary storage ? Understand what is meant by secondary storage ? Describe the operation of magnetic, optical and solid-state (flash memory) storage and give examples of each ? Describe what is meant by virtual memory, how it is created, used and why it is necessary ? Understand what is meant by cloud storage ? Explain the advantages and disadvantages of storing data on the cloud in comparison to storing it locally ? Understand that a computer needs a network interface card (NIC) to access a network ? Understand what is meant by and the purpose of a Media Access Control (MAC) address, including its structure ? Understand what is meant by and the purpose of an Internet Protocol (IP) address ? Understand that there are different types IP address ? Describe the role of a router in a network 3.1 Computer architecture A computer has many components that are needed for it to operate, but one of the most important is the CPU. This component allows the computer to process all the data that is input into it, to create an output for the user. Some systems have a smaller version of a CPU, because they don't need to be as powerful. This smaller version of a CPU is called a microprocessor. It is a type of integrated circuit that is built into a single chip. A system that uses a microprocessor is normally called an embedded system. This is a particular type of system is designed to perform a dedicated single function or a very small set of functions. This is different to a general purpose computer that will perform many different functions. Hardware 27Chapter 3 Exercise 1 Embedded systems 1 What is the main purpose of the CPU? NotUfnocr?orSMraalercestheadllPCraovofesndish2 What is a microprocessor? 3 A washing machine is an example of an embedded system. List four more embedded systems. 4 A personal computer (PC) is one example of a general purpose computer. List two other examples. Exercise 2 Fetch-decode-execute cycle A process called the fetch-decode-execute cycle is performed by the CPU. This cycle fetches an instruction into the CPU, decodes it, and then executes it. The CPU uses several different components to do this. 1 Where are data and instructions stored immediately before they are fetched into the CPU? 2 What is the purpose of a register? 28 HardwareChapter 3 3 Tick () to show which of the following components are an example of a register. Component Tick () Program counter Address busNotUfnocr?orSMraalercestheadllPCraovofesndish Memory address register Data bus Memory data register Control bus Arithmetic logic unit Control unit Current instruction register Accumulator 4 Which register stores the address of the next instruction to be fetched into the CPU? 5 What is the purpose of the memory address register (MAR)? 6 When an instruction is fetched into the CPU, which component is it sent to first? 7 What is the purpose of the control unit? 8 The arithmetic logic unit (ALU) is used to execute an instruction. It has a built-in register. What is the name and purpose of this register? Hardware 29NotUfnocr?orSMraalercestheadllPCraovofesndishChapter 3 9 Data and signals are transmitted between the different components of the CPU using buses. Can you name the three buses used for this? 10 Can you describe what happens at the fetch stage of the fetch-decode-execute cycle? 11 Can you describe what happens at the decode stage of the fetch-decode-execute cycle? 12 What is an instruction set? 30 HardwareChapter 3 Exercise 3 Components within the CPU Certain factors can affect the performance of the CPU, including the number of cores, the size of the cache, and the speed of the clock. 1 Draw a line from a component to its correct definition. NotUfnocr?orSMraalercestheadllPCraovofesndish Component Definition Clock The component within the CPU responsible for performing a single fetch-decode-execute cycle Core The component that regulates the timing and speed of a computer Cache The component that stores frequently used data and instructions 2 A student has a computer with the following specification: 2 GHz processor Dual core processor 32 kB cache Describe two ways the performance of the computer can be improved. Why would this improve the performance? Hardware 31Chapter 3 3.2 Input and output devices An input device allows data to be entered into a system to allow it to be processed. An output device allows the user to obtain the output of the processing of the data. This often involves being able to see or hear the results. NotUfnocr?orSMraalercestheadllPCraovofesndish Exercise 1 Types of input/output device 1 Tick () to show whether each device is an example of an input device or an output device. Device Input () Output () Keyboard Speaker 3D printer Barcode scanner Mouse Monitor Actuator Sensor 2 Which input device would be most suitable to enter a password into a computer? 3 Which input device would be most suitable to convert a hard copy of a document into a digital copy? 4 Which output device would be most suitable to allow shoppers to listen to an announcement in a supermarket? 32 HardwareChapter 3 5 Complete the crossword by identifying each of the sensors. 1. 1. NotUfnocr?orSMraalercestheadllPCraovofesndish2. 3. 3. 4. 4. 5. 5. 6. 6. 7. Clues Down Across 1. Can be used to measure whether a substance, such as fuel in a car, falls below a certain point. 1. Captures static forces such as the continual force of gravity and dynamic forces such as those created by vibrations. 2. Measures the presence of a magnetic force that can be emitted by an object. 2. Can be used in agriculture and farming to make sure that the produce has the correct level of watering for growing. 3. Measures how hot or cold a substance is. 3. Can be used in people homes to measure the level of 4. Measures the level of sound in a certain environment. carbon dioxide. 5. Measures the level of moisture in the atmosphere. 4. Measures the force that is directly applied to the sensor or a device by a solid, liquid or gas. 6. Can measure how much liquid is running through a pipe in a factory, 5. Measures the ambient illumination in a certain environment. 7. Can measure whether soil is acidic or alkali. 6. Can be used in a security system to capture a type of radiation emitted by an intruder. 7. Measures how close an object is to the sensor. Hardware 33Chapter 3 Sensors are used to capture data from their immediate environment. This data can then be processed by a computer system to allow monitoring and control systems to operate. 6 One benefit of sensors is that they can operate 24 hours a day, 7 days a week. List three other ways sensors can be useful. 1 2 3 3.3 Data storage NotUfnocr?orSMraalercestheadllPCraovofesndish Exercise 1 Types of storage Computers use different types of storage, including primary and secondary storage. Primary storage is directly accessed by the CPU and secondary storage is not directly accessed by the CPU. 1 Tick () to show whether each example is primary storage or secondary storage. Storage example Primary Secondary storage () storage () Read only memory (ROM) Hard disk drive (HDD) Random access memory (RAM) Solid state drive (SSD) 2 Which storage examples are directly connected to the CPU? 3 Can you name three storage examples that are described as non-volatile because they do not lose the data they store when power is turned off? 34 HardwareChapter 3 4 Does RAM or ROM store the BIOS? 5 Does RAM or ROM store the programs that are currently in use? 6 The data stored in ROM is fixed as does not normally change. Is this statement true or false? 7 It is easy to upgrade the amount of RAM in a computer by just installing more. Is this statement true or false? 8 Why does a computer system need both RAM and ROM? NotUfnocr?orSMraalercestheadllPCraovofesndish Hardware 35Chapter 3 9 Storage can be magnetic, optical, or solid state. Tick () to show whether the statement about magnetic storage is true or false. Magnetic storage Uses lasers to create pits and lands on the surface of a disk Data is stored on platters that are divided into tracks and sectors An HDD is a type of magnetic storage Uses transistors and control gates and floating gates Has a read/write head that is moved across circular plates to read/write data 10 How does solid state storage operate to store data? NotUfnocr?orSMraalercestheadllPCraovofesndish True () False () 11 How is data written to and read from a CD? 36 HardwareChapter 3 Exercise 2 Virtual memory Computers sometimes use a type of memory called virtual memory. This allows the computer to continue processing data when the RAM is full. 1 Draw a diagram that shows how virtual memory operates. NotUfnocr?orSMraalercestheadllPCraovofesndish 2 What would happen if RAM was full and a computer didn't have virtual memory that could be used? Hardware 37Chapter 3 Exercise 3 Cloud storage Cloud storage is another way to store data. Physical servers and storage devices are still used to store data in the cloud, but these belong to a third party, rather than the individual or company that owns the data. 1 In a cloud storage system is data stored locally or remotely? NotUfnocr?orSMraalercestheadllPCraovofesndish 2 List two benefits to storing data in a cloud storage system. 1 2 3 List two drawbacks of storing data in a cloud storage system. 1 2 3.4 Network hardware A network is two or more devices that have been connected using a wired or wireless connection. A range of hardware is required to create a network. Exercise 1 Components 1 (a) What is the name of the component in a computer that connects the computer to a network? 38 HardwareChapter 3 (b) What is the name of the address given to this component at the manufacturing stage? 2 Is a MAC address usually written in binary, hexadecimal or denary? 3 How is a MAC address usually created? NotUfnocr?orSMraalercestheadllPCraovofesndish 4 (a) What is the name of the network component that reads data packets and forwards them to the correct destination? (b) This component uses an internet protocol (IP) address to forward the data packets to the correct destination. (i) What is the purpose of an IP address? (ii) Can you give three features of an IP address? 1 2 3 Hardware 39Chapter 3 Revision checklist Need to revisit Satisfactory Confident NotUfnocr?orSMraalercestheadllPCraovofesndish I understand the role of the central processing unit (CPU) in a computer I understand what is meant by a microprocessor I understand the purpose of the components in a CPU, in a computer that has a Von Neumann architecture I can describe the process of the fetch-decode-execute cycle including the role of each component in the process I understand what is meant by a core, cache and clock in a CPU and explain how they can affect the performance of a CPU I understand the purpose and use of an instruction set for a CPU I can describe the purpose and characteristics of an embedded system and identify devices in which they are commonly used I can input and output devices I understand what is meant by an input device and why it is required I understand what is meant by an output device and why it is required I understand what is meant by a sensor and the purposes of sensors I can identify the type of data captured by each sensor and understand when each sensor would be used, including selecting the most suitable sensor for a given context I understand what is meant by primary storage I understand what is meant by secondary storage I can describe the operation of magnetic, optical and solid-state (flash memory) storage and give examples of each I can describe what is meant by virtual memory, how it is created, used and why it is necessary I understand what is meant by cloud storage I can explain the advantages and disadvantages of storing data on the cloud in comparison to storing it locally I understand that a computer needs a network interface card (NIC) to access a network I understand what is meant by and the purpose of a Media Access Control (MAC) address, including its structure 40 HardwareChapter 3 I understand what is meant by and the purpose of an Internet Protocol (IP) address I understand that there are different types IP address I can describe the role of a router in a network NotUfnocr?orSMraalercestheadllPCraovofesndish Hardware 41CHAPTER 4 Software NotUfnocr?orSMraalercestheadllPCraovofesndish At the end of this chapter, you will be able to: ? Describe the difference between system software and application software and provide examples of each ? Understand how hardware, firmware and an operating system are required to run applications software ? Describe the role and operation of interrupts ? Explain what is meant by a high-level language and a low-level language, including the advantages and disadvantages of each ? Understand that assembly language is a form of low-level language that uses mnemonics, and that an assembler is needed to translate an assembly language program into machine code ? Describe the operation of a compiler and an interpreter, including how high-level language is translated by each and how errors are reported ? Explain the advantages and disadvantages of a compiler and an interpreter ? Explain the role of an integrated development environment in writing program code and the common functions IDEs provide 4.1 Types of software and interrupts Software is run on the hardware of a computer system. It plays a vital part in the many tasks for which we use a computer. There are two main types of software: system software and application software. There are two categories of system software: utility software and the operating system. Exercise 1 System software and application software 1 Define what is meant by software. 42 SoftwareChapter 4 2 What is the difference between system software and application software? NotUfnocr?orSMraalercestheadllPCraovofesndish3 Circle all the examples of applications software. Word processor Anti-virus Web browser Database Disk Defragmenter Spreadsheet Compression software Back-up software Graphics editing software Presentation software Anti-malware Disk repair software 43 4 One function of the operating system is providing the user with an interface. (a) Can you give three examples of different types of interface that an operating system can provide? Can you give an example application of where each type of interface could be used? Example 1 Example application Example 2 Example application SoftwareNotUfnocr?orSMraalercestheadllPCraovofesndishChapter 4 Example 3 Example application (b) Memory management is another function that is performed by an operating system. What does the operating system do to manage the memory? (c) What are four other functions that can be performed by an operating system? Function 1 Function 2 Function 3 Function 4 44 Software

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