1 Benedict has a computer that is assigned an Internet Protocol (IP) address. The IP address is: 198.167.214.0 The IP address is represented as denary values. (a) Convert the denary values 167 and 214 from the IP address to 8-bit binary. 167 214 Working space … … … … [2] (b) Benedict’s computer is also assigned a Media Access Control (MAC) address. (i) Identify one similarity between an IP address and a MAC address. … … [1] (ii) Identify two differences between an IP address and a MAC address. Difference 1 … … … Difference 2 … … … [2]

1(a) One mark per each correct register. 1 0 1 0 0 1 1 1 1 1 0 1 0 1 1 0 2 1(b)(i) Any one from: − Both addresses can be used to identify a computer/device − Both are unique − Both can be represented as hexadecimal − Both addresses do not change if IP address is static 1 1(b)(ii) Any two from: − An IP address is assigned by the network/router/ISP, A MAC address is assigned by the manufacturer − An IP address can be changed (if dynamic), MAC address cannot be changed − IP address has 4/8 groups of values, MAC address has 6 groups/pairs of values − IP address is 32-bit/128-bit, MAC address is 48-bit − IP address does not contain serial number/manufacturer number, MAC address does − IP(v4) address is denary and MAC address is hexadecimal 2

1 A denary value can be converted into hexadecimal and binary. (a) Complete the table to show the hexadecimal and 8-bit binary values of the given denary values. Denary Hexadecimal 8-bit binary 49 123 200 [6] Working space … … … … … (b) Give two benefits, to users, of converting binary values to hexadecimal. Benefit 1 … … Benefit 2 … … [2] (c) Hexadecimal is used to represent Hypertext Markup Language (HTML) colour codes in computer science. Identify three other ways that hexadecimal is used in computer science. 1 … 2 … 3 … [3]

1(a) One mark per each correct binary value. One mark per each correct hex value. Denary Hexadecimal 8-bit binary 49 31 00110001 123 7B 01111011 200 C8 11001000 6 1(b) Any two from: − Easier/quicker to read/write/understand − Easier/quicker to identify errors/debug − Takes up less screen/display space − Less chance of making an error 2 1(c) Any three from: − MAC address − URL − Assembly language − Error codes // error messages − IP addresses − Locations in memory − Memory dumps 3

1 (a) Denary is a number system that is used by programmers. Tick (✓) one box to show whether denary is a base-2, base-10 or base-16 number system. Tick (✓) Base-2 Base-10 Base-16 [1] (b) Hexadecimal values can be used to represent denary values. Convert these four hexadecimal values into denary values. 05 … 20 … 1A … AB … [4] Working space … … … … … (c) Hexadecimal values can also be converted to binary values. Tick (✓) one box to show the correct 8-bit binary value for each hexadecimal value. (i) Hexadecimal value 25 Tick (✓) 00011001 00100101 10100001 [1] (ii) Hexadecimal value 1B Tick (✓) 00011011 10110001 00011010 [1] (d) (i) Give one way that hexadecimal is used in website development. … [1] (ii) Give one way that hexadecimal is used in low-level programming. … [1]

1(a) − Base-10 1 1(b) − 5 − 32 − 26 − 171 4 1(c)(i) − 00100101 1 1(c)(ii) − 00011011 1 1(d)(i) Any one from: − To represent HTML colour codes − In error messages 1 1(d)(ii) Any one from: − Assembly code/language − Memory address locations − In error messages − Memory dump 1

5 Sammi works for a finance company and has a laptop that he uses for his work. He has confidential data about his customers stored on his laptop. Sammi does not connect the laptop to any networks. (a) Sammi is concerned about his customers’ confidential data being viewed by other people in his office. One method he uses to prevent others viewing the data is encryption. Identify three other methods Sammi could use to prevent his customers’ confidential data being viewed. 1 … 2 … 3 … [3] (b) Sammi creates videos for the finance company website that give customers advice about their finances. He uses lossy compression to reduce the file size of the videos for the website. (i) Give three ways that lossy compression can reduce the file size of the videos. 1 … … 2 … … 3 … … [3] (ii) Give one drawback of using lossy compression to reduce the file size of the videos. … … [1] (c) Sammi could have used lossless compression to compress the videos for the website. (i) Give one reason why he would use lossless compression, rather than lossy compression, for the videos. … … [1] (ii) Give two disadvantages of Sammi using lossless compression, rather than lossy compression, for the videos. Disadvantage 1 … … Disadvantage 2 … … [2]

5(a) Any three from: − Password − Add a biometric device to the laptop // set biometric password − Use two-step verification // Use two factor authentication − Physically lock the laptop away in a secure cupboard // Taking laptop with him at all times 3 5(b)(i) Any three from: − A compression algorithm is used − The resolution could be reduced − Colour depth could be reduced // bits per pixel reduced − Sounds not heard by human ear could be removed // Perceptual music shaping can be used − Repeating frames could be removed 3 5(b)(ii) Any one from: − Quality may be reduced − Data is lost // original file cannot be reconstructed 1 5(c)(i) Any one from: − Maintains quality // quality better than lossy − Original file is retained // Data is not permanently lost − A significant reduction in file size is not required 1 5(c)(ii) Any two from: − Takes more time to transmit file // Takes more time to upload to web server // Takes more time to download to customer // Web page will load slower − Takes up more storage space − Data usage would be increased − Uses more bandwidth 2

7 A music company has a website that allows users to stream music. The music is stored in sound files. (a) The sound files are compressed using lossless compression. (i) Describe how the sound files are compressed using lossless compression. … … … … … … … … … … … [4] (ii) State one reason why the music company would compress the sound files using lossless, rather than lossy, compression. … … [1] (iii) Give one benefit, to the user, of the music company compressing the sound files. … … [1] (iv) Give one drawback of the music company using lossless, rather than lossy, compression for the sound files. … … [2] (b) Describe how the web pages for the website are requested and displayed on a user’s computer. … … … … … … … … [4] (c) The web server that hosts the website suffers a denial of service (DoS) attack. Explain why this will prevent users from accessing the website. … … … … [2]

7(a)(i) Four from: − (Compression) algorithm is used − No data will be removed // original file can be restored − Example of type of algorithm that would be used e.g. RLE − Repeated patterns in the music are identified − … and indexed NOTE: If another lossless method is described, marks can be awarded. 4 7(a)(ii) Any one from: − To provide the highest quality of music file (that compression will allow) − The user is able to listen to the original sound file − No loss of quality for the sound file provided 1 7(a)(iii) Any one from: − Allow for quicker streaming speed − Would not require as much bandwidth (to stream) − Does not need as much RAM − Smoother listening experience // less lag − Will not use as much of data allowance 1 7(a)(iv) Two from: − Streaming speed may be slower − … and may affect listening experience // buffering may occur − User may need more bandwidth to stream − … that could be more expensive − It would be a larger file size − … so may take longer to upload − … so will take up more storage space … − … on webserver 2 7(b) Any four from: − Browser sends URL to DNS − … using HTTP/HTTPS − IP address is found on DNS − DNS returns IP address to the browser − Browser sends request to web server/IP address − Web server sends web pages back to browser − Browser interprets/renders the HTML (to display web pages) − Security certificates exchanged 4 7(c) Two from: − Web server has been flooded with traffic // web server has been sent many requests at once − … so, server is brought to a halt / crashes 2

Cambridge O Level Computer Science · 2210

O-Level Computer Science (2210) Data representation past paper questions

Revise O-Level Computer Science (2210) — Data representation with real Cambridge past-paper questions grouped by topic, each shown with its marking scheme. Working one topic at a time targets exactly the skill each question tests.

49 free questions from 2016–2021, each with its marking scheme. Open the full topical bank to filter by subtopic, paper, and year.