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computer science
cambridge international as & a level computer science

Cambridge IGCSE And O Level Computer Science 2nd Edition David Watson, Helen Williams - Solutions

10 Seven terms are being described below. Name each term being described.a. A combination of software and hardware designed and programmed to work automatically without the need for human intervention.b. Devices that are mechanical and electronic structures designed to automatically carry out a
a i) Explain what is meant by the term blockchaining.ii) Describe how blockchaining is used to prevent data tampering.b i) Describe what is meant by social engineering.ii) Describe two methods used by cybercriminals to target and attack their intended victims.c i) Explain what is meant by two-step
a. Complete the following table by writing an appropriate sensor that could be used in each application being described.Each sensor chosen can only be used once.b. A vending machine dispenses cold cans of soda (at The operation and security of the vending machine is controlled by sensors and a
Data is being sent from a computer to a printer. Interrupts and buffers are used in this process.a Explain the role of buffers during the printing process.b Explain how interrupts are used in the printing process.
John is taking photographs using a smartphone. The built-in camera uses a detector with a 2048 by 1536 pixel array. The smartphone’s camera software uses a bit depth of 24 bits.a i) Explain the two terms pixel array and colour depth.Pixel
a Describe what is meant by a QR code.b A company advertising its website uses QR codes on the walls of a city metro system.Describe how a passenger using the metro system could use the QR codes to visit the company’s website.c Give one advantage and one disadvantage of using QR codes rather than
In Von Neumann architecture, both buses and registers are used.a i) Name two buses.ii) Name two registers.b Explain the purpose of the two buses and the two registers you named in part a).c Explain what is meant by a quad core processor.
a i) Describe when a check digit would be used as a verification method.ii) Give three types of error a check digit could identify.iii) Name one situation where a check digit would not act as an error detection method.b. ISBN-13 is one way of generating and verifying a check digit. The algorithm to
a i) Describe what is meant by a USB.ii) Give three differences between USB-A and USB-C.b The table below shows ticked boxes relating to types of data transmission. The following five descriptions have been missed out of the table:– data sent one bit at a time along a single channel in one
c i) Write down the two’s complement of the binary number in part bi).ii) Convert the binary number in part ci) into denary.iii) Convert the binary number in part ci) into hexadecimal.
a Convert the denary number, 112, into an 8-bit binary number.b i) Carry out a logical shift three places to the right on your answer to part a.ii) Convert the binary number in part bi) into denary.iii) Comment on your result to part bii).
3 A company offers loans to people who can answer yes to at least two of these three questions:– are you over 18? (input A)– have you over $1000.00 in the bank? (input B)– have you a full-time job? (input J)a) Write the logic expression to represent this system.b) Write the truth table to
In this question you will be given a statement followed by four possible answers.Select which of the four answers you think is correct and tick (✔) the box next to your answer.You may need to tick more than one box.a) What is the symbol for AND?b) What is meant by the term logic circuit?• a
3 A company that sells cakes is setting up a single-table database, to store information about cakes that can be ordered. The information includes, name of cake, number of portions, price of cake, main ingredients and decoration available.State, with reasons, the structure required, including names
a) Explain what is meant by Structured Query Language (SQL).b) Describe two SQL commands.
In this question you will be given a statement followed by four possible answers.Select which of the four answers you think is correct and tick (✔) the box next to your answer.You may need to tick more than one box.a) What is meant by the term table?• a collection of fields about the same
A database, StudentRoom, was set up to show the room numbers for students living in student accommodation.a) Explain why none of the fields in the database can be used as a primary key.b) State, with a reason, a field that could be added as a primary key and give an example of some sample data for
6 Using a programming language write a program to store the names of 50 people playing a game and their high scores. Output the names and the scores ordered from highest to lowest score and output the average score.Your program must include and use meaningful identifier names for– variables–
5 A sentence is to be input and stored in a variable Sentence.Write pseudocode to:– declare the variable Sentence– input the sentence– find the length of the sentence– find out how many times the letter ‘e’ occurs in the sentence.
4a) Explain what is meant by iteration.b) Describe three methods of iteration. Include examples of each method in your answer.
a) Explain what is meant by selection.b) Describe two methods of selection. Include examples of each method in your answer.
In this question you will be given a statement followed by four possible answers.Select which of the four answers you think is correct and tick (✓) the box next to your answer.a) This is a Boolean operator:• +• DIV• >=• NOTb) What is meant by the term array?• a list, for example 3, 2.7,
Tick (✓) the appropriate column, in the following table, to indicate whether the statement is assignment, selection or iteration. Statement IF Number1 < Number2 Number1 Number2 Number1 Number2 + 1 FOR Number 1 1 TO 10 CASE OF Numberl WHILE Number1 Number2 REPEAT Assignment Selection Iteration
Extend your program design (from page 120) to store each name and nickname in a two-dimensional array, the age in another array and the choice in another array. The index of the array will identify the player. Use a procedure to output the personalised welcome message for each player when all
A programmer has been asked to design and write a program to accept inputs about each game player:● name● age in years● nickname● if the player wants to use their name or their nickname.The program must include a validation check on the age, ensure the name and the nickname are no more than
Identify four errors in this algorithm. 01 NumberProducts 50 // length of array Product Name [] 02 OUTPUT "Please enter product to find " 03 INPUT Product 04 Found FALSE - 05 Counter 1 06 REPEAT + 07 IF Product = Product Name [Counter] 08 09 THEN Found FALSE 10 ELSE 11 Counter Counter - 1 12 ENDIF
Identify three types of test data. Include an example of each type in your answer with an explanation of why it is appropriate.
Explain the difference between mathematical and comparison operators. Include an example of each type in your answer.
a) Write pseudocode to input 12 numbers and store them in an array.b) Change your pseudocode to use a different loop structure.c) Identify another loop structure you could have used.d) Write pseudocode to find the largest, smallest and the average of the numbers you have stored.e) Write pseudocode
In this question you will be given a statement followed by four possible answers. Select which of the four answers you think is correct and tick (✓) the box next to your answer.a) This is a conditional statement:• Answer ← Number1 + Number2• REPEAT … UNTIL Number1 = Number2• IF Number1
Tick (✓) the appropriate column, in the following table, to indicate whether the description applies to validation, verification or neither.You may need to tick more than one column in each row. Description Ensuring a number is positive Ensuring a password is as intended Ensuring a password is
a) A computer system can be decomposed into its component parts. One of the parts is input.Identify two other component parts.b) Formal methods are used to show a proposed solution.i) Identify the formal methods shown.ii) Identify another formal method that could be used to check if the password
The program development life cycle is divided into different stages.Analysis is the first stage.a) Describe the purpose of analysis.b) Identify and describe two other stages of the program life cycle.
This diagram shows a schematic of an expert system.a) Name each of the components, 1–4.b) Describe the steps taken when setting up an expert system for the first time. User 1 Explanation system 2 3 4
9 Six statements are shown on the left, and nine computer terms are shown on the right.By drawing lines, connect each statement to its correct term.Not all computer terms will be used. Branch of computer science where cognitive behaviour of the human brain is studied. Rules base Search engine
8a) Explain each of the following terms used in machine learning.i) Stop words ii) Collaborative filtering iii) Web crawlers iv) Web scrapingb) Describe how machine learning can help to categorise an email as spam.
a) Describe the term machine learning.b) Explain how machine learning and artificial intelligence (AI)differ.(c) Describe how a search engine might use machine learning to determine the most appropriate results based on a user’s search criteria.
The following table contains ten descriptions. Complete the table by writing the computer term being described in the right-hand column. Description Attachment to a robot arm that allows it to carry out a specific task, such as welding a car body. A type of search engine used in an expert system
Autonomous buses, trams and trains are being introduced to many cities around the world.a) Explain what is meant by the term autonomous.b) Autonomous trains make use of many sensors to enable functions, such as closing and opening doors, to be done automatically.Describe three sensors that might be
Autonomous robots are used in space exploration and in undersea exploration. These robots have to either work in the near vacuum of space or the very high pressures under the oceans. They need to be equipped with many sensors and cameras to carry out their remote tasks.a) The undersea robots are
Use the following words to complete the paragraph that follows.Robots can collect data from their surroundings by using ‹ ……………. ›.The data is then sent to a ‹ …………………… › to allow the robot to build up an image of its ‹ ………………….. ›.Robots can do
a) Describe the three characteristics that must be shown by a device for it to be regarded as a robot.b) Explain the difference between dependent and independent robots.c) Describe briefly two examples of software robots.
The eight statements on the left-hand side of the table are either true or false.Tick (✓) the appropriate box to indicate which statements are true and which statements are false. Statement Automated systems lead to less consistent results or less consistent products. Automated systems are more
2a) Name suitable sensors for each of the following automated systems.i) Manufacture of a new vaccine which requires the mixing of four liquids in the ratio 1:2:3:4 as a single batch. The four liquids must be totally mixed and the temperature must be maintained at 35 °C (± 1 °C) which is a
A laboratory experiment involves the use of a burette ‘A’ adding acid to a solution in a conical flask ‘B’. As the reaction proceeds, the colour of the solution changes from yellow to red. The colour change is picked up by a sensor called a colorimeter.The amount of acid to be added is
The irrigation (watering) of crops in large areas of Brazil is now fully automated due to the vast areas covered by farms.The following diagram shows how sensors, actuators and microprocessors can be used to automatically control the irrigation system.a) Using the diagram, explain how sensors,
Describe three ways to check whether an email is from a legitimate source.
Five statements are shown on the left, and eight computer terms are shown on the right.By drawing lines, connect each statement to the correct computer term (three of the computer terms won’t be used). A type of stand-alone virus that can replicate itself; they often use networks to search out
8 Automatic software updates are used by many mobile phone companies. The following flowchart shows the procedure for updating mobile phone software automatically overnight.Seven of the boxes in the flowchart are incomplete. Use the following list of items to complete the flowchart. (You only need
7 You have been asked to write an article on cyber security threats to a computer connected to the internet.Describe four different examples of cyber security threats and explain how the risks can be mitigated against.
6 Name the eight computer terms being described below (a different answer is required for all eight parts).a) A user is granted access to a website only after successfully presenting two pieces of evidence to verify their identity.b) Makes use of a cache to speed up access to web pages on a
a) Explain why passwords are used when logging onto websites.b) Give three features you would expect to see in a strong password. Also give one example of what should be avoided when deciding on a password.c) Mikael uses a password and also uses his email address as a username to log into a secure
4 A blockchain has seven blocks.a) Draw a diagram to show how these seven blocks are all interconnected to form a blockchain. Include any values in your diagram.b) Describe what would happen if block 3 was hacked to change a sum of money or an attempt was made to divert money to a different block.
a) Explain what is meant by the term blockchaining.b) Apart from monetary transactions, name three other uses of blockchaining.
Describe the main differences and any similarities between digital currency and cryptocurrency.
The following table contains features of the internet and World Wide Web (WWW).Indicate in the right-hand column, by writing ‘internet’ or ‘WWW’ which features refer to the internet and which features refer to the WWW. Feature Ability to send and receive emails. Makes use of http and https
A URL is being entered as:https://www.frage-eins-beispiel.org.de/example-page Identify:a) the domain nameb) the domain typec) file named) protocol being used.
a) Define what is meant by a cookie.b) Describe the differences between a session cookie and a persistent cookie.c) Give three uses of persistent cookies.
9 Explain why an integrated development environment (IDE) is needed. In your answer, identify the features that are included in an IDE and the reasons why a programmer finds these features useful.
8a) Explain what is meant by an integrated development environment (IDE).b) Describe two features of an IDE.
In this question you will be given a statement followed by four possible answers.Select which of the four answers you think is correct and tick (✓) the box next to your answer.a) What is meant by the term assembly language?• A language that is dependent on computer hardware and needs to be
Tick (✓) the appropriate box in the table below to indicate whether the description applies to an assembler, a compiler and/or an interpreter.You may need to tick more than one column in each row. Description Translates a program written in a LLL. Translates a program written in a HLL. Identifies
The following paragraph has several terms missing. A list of possible terms is given below. By writing the correct term in the spaces provided, complete the paragraph.Each term in the list may be used once, more than once or not at all.An interrupt is a sent from a hardware device or to the
a) Explain why device drivers are needed. In your answer, include what information is contained in a device driver and why that information is needed.b) Describe how buffers and interrupts are used when data is being transferred from a camera (through a USB port) to a computer.
Operating systems are used to oversee the efficient and correct operation of a computer system.Describe the functions of the following parts of a typical operating system.a) Memory managementb) User account managementc) Security management
a) Explain what is meant by a virus.b) Explain how a virus checker detects and removes viruses.
Tick (✓) the appropriate column, in the following table, to indicate whether the named software is either system software or application software. Software Screensaver Antivirus software Printer driver Video editing software Compiler QR code reader On-screen calculator Operating system software
a) Human computer interfaces (HCIs) are sometimes referred to as WIMP and post-WIMP.i) Explain the difference between WIMP and post-WIMP ii) Describe the relative advantages and disadvantages of the two types of interface.b) Explain the term screensaver. Include, in your answer, the reasons why
Five descriptions of network terms are given below. In each case, name the network term being described.a) Hardware component (on a circuit board) or chip that allows a device to connect to a network, such as the internet.b) Unique identifier that acts as a network address for a device; takes the
10 A firm of architects has decided to store client drawings on the cloud thus enabling clients and architects to access the drawings(and other data) whenever they want.a) Which type of cloud storage would be most appropriate in this application?Explain your choice.b) i) Give two advantages to the
a) Describe the main differences between RAM and ROM.b) Discuss the advantages and disadvantages of increasing the size of RAM in a computer.c) Describe the differences between DVDs and Blu-ray discs.
Six statements are shown on the left, and six computer terms are shown on the right.By drawing lines, connect each statement to the correct term. Refers to RAM and ROM Secondary storage Made up of many tiny transistors in a matrix; has a control gate and floating gate at each intersection
a) Explain the difference between monitoring and control.b) An apartment has an air conditioning system which is controlled by sensors and a microprocessor. The temperature and humidity levels are constantly measured and, if either fall outside a set range, the air conditioning unit is switched
Name a suitable output device for each of the following applications.a) Produce a working model of a new toy during its development stages.b) Advertising a new product on a billboard on the approach road to a large city. The billboard will show moving images.c) Very thin screen which can be
Mobile phones use touchscreen technology.a) Name one type of touchscreen technology.b) Describe the advantages and disadvantages of the touchscreen technology named in part a).
A pharmaceutical company uses synthetic gloves to protect scientists when carrying out work in a glovebox. The gloves used have a limited operational life (a ‘use by’ date) and must be regularly checked and changed if necessary.As part of the monitoring system, each glove has a unique barcode
a) Explain the term sensor.b) Describe an application that uses magnetic field sensors.c) A chemical process only works correctly if the temperature is above 70 °C and the pH is below 3.5. Sensors are used as part of the control process. A heating element is used to heat the reaction if necessary
a) Explain what is meant by the Fetch-Decode-Execute cycle.b) Describe three actions that take place during the Fetch-Decode-Execute cycle.
Give three benefits and three drawbacks of using embedded systems in household devices.
Five statements are shown on the left, and five computer terms on the right.By drawing lines, connect each statement to the correct computer term.. Ensures correct synchronisation of all computer operations Can improve the performance of the CPU by increasing its width Temporary storage space that
a) Describe the role of registers and buses in a typical computer system. b) Discuss four ways to improve the performance of a CPU in a computer system.
Define the following computer terms.a) Ciphertextb) Plaintextc) Encryptiond) Private keye) Encryption algorithm
Ali and Daniel both work for an international company. Ali wishes to send Daniel a confidential document over the internet.a) Describe how Ali and Daniel would use matching pairs of keys to ensure the document is sent safely over the internet.b) Explain what needs to happen if Daniel wants to
Explain why asymmetric encryption is safer than symmetric encryption when sending data over the internet.
a) The following block of data was received after transmission from a remote computer. Even parity protocol was being followed by both computers. One of the transmitted bits has become changed following transmission.i) Locate which bit was changed and which byte was affected.ii) Write down the
Nine descriptions about error checking methods are given in the table below. By ticking (✓) in the appropriate column or columns, indicate whether each description refers to checksum, parity check, ARQ or CRC. It is possible more than one column, or none of the columns, can be ticked for each
a) Explain how Automatic Repeat Request (ARQ) can be used to detect errors following data transmission.b) Explain why echo check is not a very reliable method for detecting errors.
Four statements about data transmission are shown in the following table.Tick (✓) the appropriate columns to indicate the method and direction of data transmission being described by each statement. Statement Data is being sent in both directions, one bit at a time along a single wire, but not at
Explain what is meant by the following four terms:a) Data skewingb) USB-C connectionc) Parallel data transmissiond) Half-duplex data transmission
2 Data being shared between two computers is split up into a number of data packets prior to transmission. The data packets contain a header and a trailer.a) Give three pieces of information found in the header.b) The trailer contains a cyclic redundancy check (CRC).i) Name another item found in
1 Explain how packet switching could be used to download some software from a website.
A video conference is taking place between delegates in the USA and Mauritius. Packet switching is used to send video and sound data between delegates.Describe:a) the potential problems with sound and video qualityb) how the problems in parta) could be overcome.
When zooming in to an image (that is, increasing its size on screen), it may become pixelated.a) What is meant by the term pixelated?b) Explain why an image can become pixelated.c) Colour images are made up of red, green and blue elements.Each of the three colour elements can be represented by 256
A student gave the following answers in an end-of-term test on computer science. In each case, explain why the student’s answers were incorrect. Also suggest what answer the student should have given in each case.a) 1 MiB is equivalent to 1 000 000 bytes of data.b) A file which undergoes a lossy
Explain the following four terms:a) MP3 fileb) JPEG filec) 1 Tebibyted) pixel
An ancient Roman mosaic was being scanned by archaeologists and the pattern saved on a computer. Each black tile has the binary value 0 and each white tile has the binary value 1.a) What is the file size of the raw data?b) Describe how run length encoding (RLE) could be used to reduce the size of
The following diagram shows the sampling of a sound source:a) What type of data is natural sound?b) The sound resolution being used is 16 bits. Write down the binary values of i) peak ‘A’ and peak ‘B’;ii) peak ‘B’ has two potential values; describe how this problem could be resolved. c)
i) Explain the two terms lossy and lossless file compression. ii) Give two advantages of compressing files and data. iii) Give one drawback of using lossy file compression and one drawback of using lossless file compression.
A camera detector has an array of 2048 by 3072 pixels and uses a colour depth of 32 bits. The camera has a 64 GiB memory capacity.Calculate how many typical images could be stored on the camera.
a) i) Convert the denary number 116 into a binary 8-bit number.ii) Carry out a logical shift two places to the right on the binary number obtained in part a)i).iii) Carry out a logical shift three places to the left on the binary number obtained in part a)i). Comment on your answer. b) i)

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