1 DL EdExcel TextBook Questions and Answers edited with ...€¦ · ... pseudocode, structured English ... [quick sort, bubble sort, selection sort, ... Complete the instructions

Edexcel GCSE Computer Science Page 1 of 42

1 Algorithms 4

Learning outcomes 4

Referenced to 4

Student’s Book answers 4

2 Decomposition 6

Learning outcomes 6

Referenced to 6

3 Developing code 7

Learning outcomes 7

Referenced to 7


4 Constructs 12

Learning outcomes 12

Referenced to 12

5 Data types and structures 13


Referenced to 13


6 Input/output 15


Referenced to 15


7 Operators 17


Referenced to 17


8 Subprograms 19


Referenced to 19


9 Binary 20


Referenced to 20


10 Data representation 22



Referenced to 22


11 Data storage and compression 24


Referenced to 24


12 Encryption 25


Referenced to 25


13 Databases 26


Referenced to 26


14 Machines and computational models 27


Referenced to 27

15 Hardware 28


Referenced to 28


16 Logic 34


Referenced to 34

17 Software 35


Referenced to 35


18 Programming languages 37


Referenced to 37


19 Networks and the world wide web 38


Referenced to 38



20 Emerging trends, issues and impact 40


Referenced to 40



1 Algorithms

Learning outcomes

• Understand what an algorithm is, what algorithms are used for and be able to interpret algorithms [flowcharts, pseudocode, structured English, written descriptions, program code]

• Be able to create an algorithm to solve a particular problem, making use of programming constructs [sequence, selection, repetition] and using an appropriate notation [flowchart, written description, program code]

• Be able to describe the purpose of a given algorithm and explain how a simple algorithm works • Be able to identify the correct output of an algorithm for a given set of data • Be able to identify and correct errors in algorithms • Be able to code an algorithm into a high-level language • Understand how the choice of algorithm is influenced by the data structure and data values that

need to be manipulated • Understand how standard algorithms [quick sort, bubble sort, selection sort, linear search, binary

search, breadth first search, depth first search, maximum/minimum, mean, count] work

Referenced to

Specification 1.1 Student’s Book 1

Student’s Book answers

Page 3 Question What is an algorithm? Answer An algorithm is a set of specific steps for solving a category of problems. Page 7 Question Briefly describe the following constructs: • sequence • selection • iteration. Answer Sequence

• A sequence is a linear progression where one task is performed sequentially after another. Selection


• IF–THEN–ELSE is a decision (selection) in which a choice is made between two alternative

courses of action. Iteration

• WHILE is a loop (repetition) with a simple conditional test at its beginning. Page 9 Question Why would a computer programmer want to use a flowchart during a design process? Answer Solutions to simple programming exercises can be often designed and implemented by just sitting down and writing code. It is, however, extremely difficult to write solutions to complex problems using this approach and they are impossible to debug. For these reasons a structured design process is preferred. Page 19 Question Complete the instructions on the flowchart by adding notes on how to play the game of snakes and ladders. Answer

Page 22 Question What is a variable? Answer In computer programming, a variable is a storage location and name (called an identifier) which contains some known or unknown quantity of information, a value.


2 Decomposition

Learning outcomes

• Be able to analyse a problem, investigate requirements [inputs, outputs, processing, initialisation] and design solutions

• Be able to decompose a problem into smaller sub-problems

Referenced to



3 Developing code

Learning outcomes

• Be able to write programs in a high-level programming language • Understand the benefit of producing programs that are easy to read, and be able to use

techniques [comments, descriptive variable names, indentation] to improve readability and to explain how the code works

• Be able to differentiate between types of error in programs [logic, syntax, runtime] • Be able to design and use test plans and test data • Be able to interpret error messages and identify, locate and fix errors in a program • Be able to identify what value a variable will hold at a given point in a program [trace table] • Be able to make effective use of tools offered in an integrated development environment

[watcher, break points, single-step, step throughs] • Be able to evaluate the strengths and weaknesses of a program and suggest improvements • Be able to work safely, respectfully, responsibly and securely when using computers

Referenced to



Page 38 Question What is a high-level programming language? Answer A high-level programming language is a language which enables a programmer to write programs that are close to human language. This makes the coding easier to both read and write. Page 39 Question Describe the main benefits to a programmer of using a high-level programming language. Answer It makes it much easier to code and check as the language is easy to understand. Question Describe the difference between an interpreter and a compiler. Answer Compilers were the first sort of translator program to be developed. The idea is simple – the program is written in a high-level language and then the compiler translates it. You can then run


the result. An interpreter is also a program that translates a high-level language into a low-level language, but it does it when the program is actually run. You can write the program using a text editor and then simply instruct the interpreter to run the program. Page 40 Question What is a comment? Answer In computer programming, a comment is used to annotate code. It does not run. Question Describe the main reasons why programmers would wish to annotate or add comments to their code. Answer Comments are usually added with the purpose of making the source code easier to understand. Comments have a wide range of potential uses from adding descriptions of what is happening to generating external documentation. Page 41 Question Describe the main reasons why it is important to choose descriptive names for variables. Answer Adding descriptive variable names improves the overall quality of the software. It makes it much easier to modify and read the code. Page 42 Question What does this function return? <code> list(range(10)) </code>>>> list(range(10)) Answer 0 1 2 3 4 5 6 7 8 9 Page 43 Question What is a runtime error?


Answer Runtime errors occur whenever the program instructs the computer to carry out an operation that it is either not designed to do or reluctant to do. As a consequence of the huge number of situations that can be categorised within this area, there is equally a huge number of ways to write programs that cause runtime errors. Question Explain the following statement: ‘Run-time Error 339 component MCI32.OCX or one of its dependencies is not correctly registered: a file is missing or invalid.’ Answer There is a runtime error due to a missing file or piece of code. Page 44 Question What is meant by a logical error? Answer The program will run successfully; however, it will not behave in the manner it was designed to. In other words, it will simply produce incorrect results. Question A programmer is developing a new program. Describe the types of errors he or she should check for. Answer There are basically three types of error that computer programmers encounter when writing software. These are:

• Syntax errors

Syntax errors, or as they are sometimes known, format errors, are a big problem for those who are new to programming. A syntax error occurs when the programmer fails to obey, usually through inexperience, one of the grammar rules of the programming language that they are writing their application in.

• Runtime errors

Runtime errors occur whenever the program instructs the computer to carry out an operation that it is either not designed to do or reluctant to do.

• Logic errors

Out of the three common errors that occur in programming, logic errors are typically the most difficult kind of errors to detect and rectify. This is usually because there is no obvious indication of the error within the software.


Page 50 Question Explain the differences between verification and validation. Answer Verification is the testing of conformance and consistency of software against pre-decided criteria. So it could be looked upon as asking the question: ‘Have we built the product right?’ This is usually carried out via functional testing, where testing activities verify the specific actions or functions of software code relative to an expected response.

When we check that an application has been correctly written against a specification that has been agreed with the customer it is called validation. So it could be looked upon as asking the question: ‘Have we built the right product?’ Validation is commonly tested via non-functional testing that may not have any relation to a specific function or user action. Page 51 Question Describe the two main types of program testing. Answer 1. Under normal conditions. The application is tested under normal working conditions and the

data that a coded solution is supplied with is within the anticipated range. This includes testing under extreme conditions – the coded solution is provided with data that is within the operating range but at its limits of performance.

2. Error behaviour. An application or program is provided with data that is outside of its limits of

performance. These particular tests try to break the application and to investigate if things occur when they shouldn’t or vice versa.

Page 55 Question Describe three essential safety practices when using computers on a daily basis. Answer

• Observe recommendations for the health and safety of the user.

• Take care when handling hardware components.

• Ensure that any computer settings can be reversed if necessary.

• Make use of IT security – passwords, anti-virus software, etc.

Page 56 Question Describe three main security measures required when using an internet-connected computer.


Answer Use strong passwords, keep anti-virus software and security patches up to date, log out of services when we finish using them, and be careful of the information we send in emails, texts or instant messages. The only time anything is private in computing is when the computer is off line. Never put any private information on the internet. Page 57 Question What is meant by the terms legal and ethical use in relation to computer software? Answer Legal use – illegally downloading copyrighted material like movies, music, publications, software and video games. Ethical use – it is unethical to access, view or collect confidential material and/or personal information.


4 Constructs

Learning outcomes

• Be able to identify the structural components of a program [variable and type declarations, initialisations, command sequences, conditionals, repetition, data structures, subprograms]

• Be able to use sequencing, selection and repetition constructs in programs

Referenced to



5 Data types and structures

Learning outcomes

• Understand the need for and be able to select and use data types [integer, real, Boolean, char] • Understand the need for and be able to select and use data structures [one-dimensional arrays,

two-dimensional arrays] • Understand the need for and be able to manipulate strings • Understand the need for and be able to use variables and constants • Understand the need for and be able to use global and local variables

Referenced to



Page 66 Question Which of the following are integers: 6, –7.0, 2.6, 10, 4.5. 17. 17.0 Answer 6, –7.0, 10, 17.0 Question What is the difference between integer and real data types? Answer Integer data types contain whole numbers (not fractional numbers). Real data types contain decimal numbers. Both types can be positive, negative, or zero. Page 72 Question Explain the term one-dimensional array. Answer A one-dimensional array in Python and PHP is a data structure that allows a list of items to be stored with the capability of accessing each item by pointing to its location within the array.


Page 76 Question Explain the difference between one- and two-dimensional arrays. Answer

Two-dimensional arrays are a little more complex than one-dimensional arrays, but really they are nothing more than an array of arrays. In other words, there is an array in one row and another in the next row. Page 78 Question Draw a binary tree to show the possible outcomes of tossing a coin eight separate times in terms of heads and tails. Answer

Page 83 Question Describe two kinds of scope used in programming. Answer Module scope – refers to when a variable is declared before and outside of any procedure within a program module. Procedure scope – refers to when a variable can be read and modified only from within the procedure in which it is declared.


6 Input/output

Learning outcomes

• Be able to write code that accepts and responds appropriately to user input • Understand the need for and be able to implement validation • Be able to write code that outputs information to a screen and understand and use Cartesian x/y

coordinates • Be able to design and code a user interface [textual, graphical] • Be able to write code that opens/closes, reads/writes, deletes, inserts, appends from/to a file

Referenced to



Page 89 Question List six input devices. Answer Mouse Keyboard Touch screen Microphone Camera Tracker ball Page 90 Question List six output devices. Answer Screen Printer Speaker Plotter Data projector Actuator Page 92


Question State four types of data validation. Answer There are a number of validation types that can be used to check the data that is being entered.

• Check digit: the last one or two digits in any code are used to check the other digits are correct. • Format check: checks the data is in the specified format. • Batch totals check: checks for missing records. • Cardinality check: checks that a record has a valid number of related records. • Length check: checks the data isn't too long or too short. • Presence check: checks that some data has been entered into a field. • Consistency check: checks fields to ensure data in these fields corresponds, e.g., If Title = ‘Mr’,

then Gender = ‘M’. • Lookup table: looks up acceptable values in a table or array. • Range check: checks that a value falls within a specified range. • Spell check: looks up words in a dictionary or array. Page 93 Question List the values for each of the points in this chart. As an example, point_A is (–1,4).

Answer B is (4, 3) C is (–3, 3) D is (–2, 1) E is (2, 2) F is (–3, –1) G is (–1, –3) H is (2, –2) I is (1, –3) K is (3, –4)


7 Operators

Learning outcomes

• Understand the purpose of and be able to use arithmetic operators [plus, minus, divide, multiply, modulus, integer division]

• Understand the purpose of and be able to use relational operators [equal to, less than, greater than, not equal to, less than or equal to, greater than or equal to]

• Understand the purpose of and be able to use Boolean operators [AND, OR, NOT]

Referenced to



Page 100 Question Identify the Boolean expressions in the following:

• When the door is open and it is cold outside I have to wear my coat.

• The central heating switches off when it is higher than 22 °C and switches on when it is less than 18 °C.

Answer

• if door open AND cold outside = coat

• temp>22=off temp<18=on Question Write the following as a Boolean expression. ‘When the ground is dry and the sun goes down I water the plants. If the sun is hot and you water the plants it burns their leaves.’ Answer

if ground dry AND sun down = water plants if sun hot AND water plants = burnt leaves Page 101 Question Which of the following data would you store as an integer and which would you store as a string?

• Steve

• 15


• 007

• B901LK

• 2012

• 10.2

• marks Which is the odd one out and what would you store it as? Answer String: Steve 007 B901LK marks Integer: 2012 15 10.2 is the odd one out – This would be stored as Real because of the decimal point. Page 103 Question State three reasons why programmers use functions. Answer

• Reusability: once a function is defined, it can be used over and over again. • Many functions have already been written for you as preset functions. • Functions also provide a tool for splitting systems into parts that each have a well-defined role. Page 104 Question Explain what is meant by the scope of a variable. Answer

Variables have a global or local ‘scope’. For example, variables declared within functions may be only used in these functions. Global variables, variables declared outside, may be used anywhere within the program. If a local variable is declared with the same name as a global variable, the program will use the local variable to make its calculations within the current scope. Question Why do we use constants in programs? Answer Constants are data entities, the values of which cannot change during a program’s execution. As their name implies, their values are constant.


8 Subprograms

Learning outcomes

• Understand the benefits of using subprograms and be able to write code that uses user-written and pre-existing [built-in, library] subprograms

• Understand the concept of passing data into and out of subprograms [procedures, functions, return values]

• Be able to create subprograms that perform generalisation

Referenced to



Page 113 Question What are the two main roles of a function? Answer

• To reduce the amount of code needed.

• To split systems into parts with well-defined roles.


9 Binary

Learning outcomes

• Understand that computers use binary to represent data and instructions • Understand how computers represent and manipulate numbers [unsigned integers, signed

integers (sign and magnitude, two’s complement) real numbers] • Be able to convert between binary and denary whole numbers (0–255) and vice versa • Be able to perform binary arithmetic [add, subtract, multiply] and understand the concept of

overflow • Understand why hexadecimal notation is used and be able to convert between hexadecimal and

binary and vice versa

Referenced to



Page 119 Question What is a program written using binary codes called?

Answer Machine language Page 122 Questions 1 Write the binary code for the denary number 67. Use seven binary digits. 2 Give one reason why we use binary to represent data in computers. 3 Convert 2000 from decimal to hexadecimal. 4 Convert 3C from hexadecimal to decimal. 5 Convert 1010 0111 1011 from binary to hexadecimal. 6 Convert 7D0 from hexadecimal to binary. 7 If you shift a hexadecimal number to the left by one digit, how many times larger is the resulting number? 8 State the denary representation of the hexadecimal number D48. Answers 1 100 0011 2 Computer data can only have two states, on or off. 3 7D0 4 60 5 A7B 6 0111 1101 0000


7 16 times larger 8 3400


10 Data representation

Learning outcomes

• Understand how computers encode characters [ASCII, Unicode] • Understand how bitmap images are represented in binary [pixels, resolution, colour depth] • Understand how analogue data [sound, temperature, light intensity] is represented in binary • Understand the limitations of binary representation of data [quantisation, sampling frequency]

and how bit length constrains the range of values that can be represented

Referenced to



Page 126 Question What do we mean by image size? Answer Image size is based on the number of pixels used to make up the image. Page 127 Question How does the resolution of an image affect the size of the file? Answer The more pixels the larger the file size. Page 130 Question If an image has its colour depth decreased what is the effect? Answer Although colour depth affects the amount of memory a picture requires, it does not affect the size at which the image is displayed. It has a major effect on the quality of the image. Question What metadata is stored with an image file?


Answer Colour depth and pixels Page 131 Question How many colours can be represented using a 4-bit colour depth? Answer There are 16 colours in the 4-bit pixel system. Colour depth or bit depth is the number of binary bits that are required to define the colour of each pixel in an image. Images that are defined using pixels are called digital images. Page 134 Question How does the sample rate affect the quality of the playback for an MP3 sound track? Answer The higher the sample rate the better the quality. Question What effect does a high bit rate have on the number of sound files that can be stored on a CD? Answer As the bit rate increases the file size increases.


11 Data storage and compression

Learning outcomes

• Understand and be able to convert between the terms: bit, nibble, byte, kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB)

• Understand the need for data compression and methods of compressing data [lossless, lossy] and that JPEG and MP3 are examples of lossy algorithms

• Understand how a lossless, run-length encoding [RLE] algorithm works • Understand that file storage is measured in bytes and that data transmission is measured in bits

per second, and be able to calculate the time required to transmit a file and storage requirements for files

Referenced to



Page 136 Question What is the mathematical difference between a megabyte and a terabyte? Answer A megabyte is 1,048,576 bytes or (it is easier to remember as 1024 kilobytes). A terabyte is 1024 gigabytes or 1,048,576 megabytes. Page 143 Question What is file compression? Answer File compression is a process of ‘compressing’ a file (or files) so that they use less disk space. Compression works by reducing redundancy in a file's code. Compression software also allows you to take many files and compress them into one small file.


12 Encryption

Learning outcomes

• Understand the need for data encryption • Understand how a Caesar cipher algorithm works

Referenced to



Page 147 Question If a shift key of 2 has been used, decipher the following Caesar cipher: gzco swguvkqp Answer exam question


13 Databases

Learning outcomes

• Understand the characteristics of structured and unstructured data • Understand that data can be decomposed and organised in a structured database [tables,

records, fields, relationships, keys] • Understand the need for and be able to use SQL statements

Referenced to



Page 150 Question Data handling applications usually work through a DBMS. What is a DBMS and why is it used? Answer Database Management System Page 157 Question What type of business software lets users query data and generate forms? Answer Structured query language (SQL)


14 Machines and computational models

Learning outcomes

• Understand the concept of a computer as a hardware machine or as a virtual machine • Understand that there is a range of computational models [sequential, parallel, multi-agent] • Understand the input–process–output model

Referenced to



15 Hardware

Learning outcomes

• Understand the function of hardware components of a computer system [processor (CPU), memory, secondary storage, input devices, output devices] and how they work together

• Understand the concept of a stored program and the role of components of the processor [control unit (CU), arithmetic/logic unit (ALU), registers, clock, address bus, data bus] in the fetch–decode–execute cycle

• Understand the function of assembly code and be able to interpret a block of assembly code using a given set of commands

• Understand how data is stored on physical devices [magnetic, optical, solid state] • Understand how microcontrollers can be programmed to control actuators and take input from

sensors

Referenced to



Page 168 Question What is the purpose of the CPU? Answer

The CPU is the brains of the computer. It controls resources and computes data. Question Define a system. Answer A system is the collection of hardware that makes up a computer.

Page 171 Question What is a chip and how is it attached to the computer? Answer A computer chip, also called chip, is an integrated circuit (small wafer) made of semiconductor material and embedded with integrated circuitry to create the CPU. Chips now comprise of the processing and memory units of the modern digital computer.


Page 173 Question What does the arithmetic logic unit (ALU) do?

Answer It performs arithmetic and logic operations on data. Question What is clock speed and how is it measured? Answer Clock speed is the speed of the CPU, measured in megahertz (MHz) or gigahertz (GHz). Page 174 Question What is a clock cycle and why is it important? Answer

The speed of a computer processor, or CPU, is determined by the clock cycle, which is the amount of time between two pulses of an oscillator. Generally speaking, the higher the number of pulses per second, the faster the computer processor will be able to process information. The clock speed is measured in hertz, typically either megahertz (MHz) or gigahertz (GHz). For example, a 4 GHz processor performs 4,000,000,000 clock cycles per second. Question What are the main differences between the processors used in mobile devices and desktop computers? Answer

Mobile devices need a smaller and cooler running processor, which often has other functions too, such as phone cellular data roles. This is because the device is small and has no space for cooling fans. The clock speed is lower in mobile devices as this lowers the amount of heat they produce. Page 175 Question What is meant by dual-core processor? Answer A dual-core processor is a CPU with two processors or ‘execution cores’ in the same integrated circuit. Each processor has its own cache and controller.


Page 176 Question What is virtual memory and why is it needed? Answer By creating virtual RAM on the hard drive it speeds up the computer. It is slower than real RAM but helps with usable code needed at the time of running the program. Question Describe the difference between ROM and RAM and how these are used in a computer. Answer Read-only memory or ROM is a form of data storage that cannot be easily altered or reprogrammed. Random access memory or RAM is volatile memory and the contents are lost when the power is turned off. ROM is non-volatile and the contents are retained even after the power is switched off. RAM is a form of data storage that can be accessed randomly at any time, in any order and from any physical location. RAM is measured in megabytes and the speed is measured in nanoseconds. RAM chips can read data faster than ROM chips. Page 177 Questions 1 Why is locality important when dealing with cache? 2 Explain the purpose of level 2 cache (L2). Answers

1 When the CPU accesses a particular location, the cache knows that it is likely to need to access data that is close to that locality again. 2 Level 2 cache, also called secondary cache, is a memory that is used to store recently accessed information. The goal of having the level 2 cache is to reduce data-access time in cases when the same data has already been accessed. Page 180 Questions 1 Explain why some data is stored in RAM when you are running a program. 2 What kind of computer memory is both static and non-volatile? Answers

1 Random access memory, or RAM, most commonly refers to computer chips that temporarily store dynamic data to enhance computer performance. By storing frequently used or active files here, the computer can access the data faster than if it had to retrieve it from the far larger hard drive. RAM is also used in printers and other devices.


2 Read-only memory (ROM) consists of a programmed integrated circuit that doesn't lose data when powered down, making it non-volatile. But the data is also relatively static – it stays the same over time. Page 181 Question What is the difference between DRAM and RAM? Answer

RAM (random access memory) is a generic name for any sort of read/write memory that can be randomly accessed. There are many different kinds of RAM. One of them is DRAM, which stands for Dynamic RAM. SRAM – static random access memory – is another type of RAM. RAM / SRAM requires six transistors to create a memory cell. DRAM requires one transistor to create a memory cell. Question What type of memory is a USB drive and how does it work? Answer

A memory stick uses flash memory, which uses a transistor that stays switched on (or off) when the power is turned off. Flash memory can be erased and rewritten many times. Page 182 Question When your computer’s speed begins to drop, explain which element of memory is likely to be almost full and describe how to improve the computer’s memory performance. Answer

Some people incorrectly think that the clock speed of the CPU determines which computers are ‘fast’, but this only works when comparing CPUs in the same family. Providing the hard disk has lots of room, when your computer slows down it is likely that the RAM is too small, so adding extra RAM is the best way to speed up a computer. This will increase the speed of performance of all tasks, such as web surfing and email, as well as the times it takes to open programs. It will also allow more programs to run simultaneously without slowing down. Question Explain a computer’s memory hierarchy. Answer

There are four major memory storage levels, called the memory hierarchy. As we go down the list, access times increase:

• Internal – processor registers and cache

• Main – the system RAM and controller cards

• Online mass storage – secondary storage


• Offline bulk storage – tertiary and offline storage. Question While a computer is working what is stored in RAM? Answer The RAM (random access memory) does not store anything. It contains those items which are being processed. If you are typing something, the typed material is stored in the RAM until you save the file. RAM most commonly refers to computer chips that temporarily store dynamic data to enhance computer performance. By storing frequently used or active files here, the computer can access the data faster than if it had to retrieve it from the far-larger hard drive. RAM is also used in printers and other devices. Questions 1 How does virtual memory free up RAM? 2 Explain the term latency. Answers

1 This is achieved by putting some sections of RAM on the hard disk. It is slower (latency times are extended) but the RAM capacity is extended as well, which helps with usable code needed at the time of running the program. 2 Latency is a delay in transmitting data between a computer’s RAM and its processor. Because RAM is not fast compared to the computer's processor, RAM latency can occur, causing a delay between the time a computer's hardware recognises the need for a RAM and the time the data or instruction is available to the processor. If the CPU requests data that is not stored in the cache, then it will have to wait for the RAM to retrieve the data, causing latency problems. Page 184 Question In the world of computing, what is bus width? Answer

Bus width refers to the number of bits that can be sent to the CPU simultaneously, and bus speed refers to the number of times a group of bits can be sent each second. Question What is the brain of the computer called? Answer

The central processing unit (CPU).


Page 185 Question Why does a computer have both RAM and cache memory? Answer Cache is much quicker than RAM but is smaller so a computer needs both. Page 187 Question Typically, what technology do hard disk drives employ as a storage mechanism? Answer

Magnetic storage on a spinning disk. Page 189 Question Why is there a limited number of tracks on an audio CD? Answer Storage size on a CD is limited so only a limited number of tracks can be stored. Page 191 Question Describe the benefits and drawbacks of a using traditional magnetic hard disk drive in a laptop computer compared to a solid-state hard drive.

Answer Traditional magnetic hard drives are much cheaper than solid-state drives, and have much more storage space. But they are heavier and slower, and can develop faults if the laptop is dropped.


16 Logic

Learning outcomes

• Be able to construct truth tables for a given logic statement [AND, OR, NOT] • Be able to produce logic statements for a given problem

Referenced to



17 Software

Learning outcomes

• Understand what an operating system is and its functions [file management, input/output, resource allocation, process management, network management, user management]

• Understand that application software such as a web browser, word processor, spreadsheet or apps are computer programs

• Understand how software can be used to simulate and model aspects of the real world and be able to create software models

Referenced to



Page 200 Question State three examples of operating systems which are used in different computer devices. Answer • Windows • Windows CE • Macintosh OS X (Mac OS X) • iOS (iPhoneOS) • Linux • Android Phone • Blackberry (RIM OS) • Solaris (SunOS) • AIX • IOS (Cisco) • XOS (Extreme Networks) • IronWare OS (Foundry) Question What is operating system software? Answer

The main purpose of an operating system is to allocate resources such as memory to programs and control this allocation. It also manages the security of the computer system and data flow as well as managing the running of one program at a time.


Page 202 Question What is a supercomputer and what is it used for? Answer A supercomputer is the fastest type of computer. Supercomputers are very expensive and are employed for specialised applications. Examples of use include weather forecasting, animated graphics, fluid dynamic calculations and nuclear energy research.


18 Programming languages

Learning outcomes

• Understand what is meant by high-level and low-level programming languages and assess their suitability for a particular task

• Understand what is meant by a compiler and an interpreter

Referenced to



Page 203 Question What are the advantages of writing in high-level code compared to machine code? Answer High-level code is more understandable than machine code to humans, so it makes the process of developing a program easier. Page 204 Question Describe the differences between a high-level language and an assembly language. Answer Assembly languages are a low-level programming language in which the sequence of 0s and 1s are replaced by mnemonic codes. High-level languages are English-like statements and programs written in these languages need to be translated into machine language before their execution using a system software compiler. Page 207 Question What is a low-level programming language? Answer A low-level language is closer to how the computer works.


19 Networks and the world wide web

Learning outcomes

• Understand why computers are connected in a network • Understand the different types of networks [LAN, WAN, PAN, VPN] • Understand the network media [copper cable, fibre optic cable, wireless] • Understand that network data speeds are measured in bits per second [Mbps, Gbps] • Understand the role of and need for network protocols • Understand that data can be transmitted over networks using packets [TCP/IP] • Understand the need to detect and correct errors in data transmission [check sums] • Understand the concept of and need for network addressing and host names [MAC addresses] • Understand the characteristics of network topologies [bus, ring, star, mesh] • Understand what is meant by the internet and how the internet is structured [IP addressing,

routers, connecting backbone, domain names] • Understand what is meant by the world wide web (WWW) and components of the WWW [web

server URLs, ISP, HTTP, HTTPS, HTML] • Be able to use HTML and CSS to construct web pages [formatting, links, images, media, layout,

styles, lists] • Understand the client–server model, the difference between client-side and server-side

processing and the role of cookies

Referenced to

Specification 5.1 and 5.2 Student’s Book 19

Student’s Book answers Page 211 Question Describe the type of network that is suitable for 10 or more users. Answer Any of the networks could potentially be used, depending on geographic location, security needs, and budget. For example, if the users are geographically spread and require a secure system from a range of locations, a VPN would be the best system. Page 213 Question What is the difference between a LAN and a WAN? Answer Local Area Networks (LANs) are characterised by high-speed transmission over a restricted geographical area. If the LAN is too large, signals need to be boosted.


While LANs operate where distances are relatively small, wide area networks (WANs) are used to link LANs that are separated by large distances that range from a few tens of metres to thousands of kilometres. Page 221 Question What is meant by a network protocol? Answer A protocol is, in one sense, nothing more than an agreement that a particular type of data will be formatted in a particular manner. Question What is an IP address? Answer An internet protocol address (IP address) is a numerical address assigned to each device (e.g., computer, printer) connected in a computer network. Page 222 Question What is the purpose of a router on a network? Answer Routers are small devices that join multiple networks together. A router connects two or more networks. Page 227 Question What is a token? Answer A token is a protocol. Tokens are the method by which all networked computers set up a link through some kind of networking equipment.


20 Emerging trends, issues and impact

Learning outcomes

• Be aware of current and emerging trends in computing technology [quantum computing, DNA computing, artificial intelligence (AI), nano technology]

• Be aware of the impact of computing on individuals, society and the environment • Be aware of ethical and legal issues arising from the use of computers • Be aware of ownership issues relating to computing [intellectual property, patents, licensing,

open source and proprietary software]

Referenced to



Page 236 Question Explain the term encryption. Answer Encryption is the coding or scrambling of information so that it can only be decoded and read by someone who has the correct decoding key. Page 238 Question Explain three instances in everyday objects that you personally use where time between failures could be critical. Answer

• Modern cars have computer-controlled steering, if the computer failed you could be killed.

• Aircraft are now fly-by-wire, and failure would be critical.

• Nuclear power plants are all computer controlled. A failure could be catastrophic.

Page 239 Question What is a bug? Answer A bug is an error in a computer program.


Question Explain two different types of redundancy in computing. Answer

Data redundancy: This is a strategy whereby important data is duplicated in a number of places within the computer system so that if one area of the system breaks down or becomes corrupted the data will not be lost. An example of this is running two hard disk drives in parallel, where they both store the same data. Software redundancy: This less common strategy tends to be used for safety critical applications. The purpose of software redundancy is that it is very difficult to create programs that don’t contain any bugs at all, and in the event of a bizarre fault an undetected bug may cause disastrous consequences. Therefore, for critical software where failure cannot happen, there will be three software routines in place – each written by independent programming teams – each producing the same output when the same input is applied. Page 240 Question List five criteria that you would need to consider in developing a policy for backing up your data. Answer

• Amount of data to back up

• How often to back up

• Best type of storage media

• How long to keep backups for

• Manual or automatic backup. Page 242 Question Describe the benefits and drawbacks to a rural school in moving to a cloud-computing model. Answer A small school in the countryside may have limited bandwidth. If this is the case, cloud computing is not a good idea. The advantages of cloud computing are that students are able to access their work anywhere, even at home; software will always be up to date; and the school will not need a technician to manage its systems. Question What are the implications of cloud computing to computer programmers?


Answer Cloud computing has led to a major change in how we back up data, store information and run applications. Instead of installing applications (often referred to as apps) on individual computers, everything can be hosted in the ‘cloud’. Cloud computing has led to a major change in how we back up data, store information and run applications. Instead of installing applications (often referred to as apps) on individual computers, everything can be hosted in the ‘cloud’. Computer programmers have to design a different way of limiting a client–server model. They also need to use different programming languages.

Documents

1 DL EdExcel TextBook Questions and Answers edited with ...€¦ · ... pseudocode, structured English ... [quick sort, bubble sort, selection sort, ... Complete the instructions