1 A hockey club records the number of people that watch each match. An 8-bit binary register is used to store this value. (a) 46 people watch the first match and 171 people watch the second match. Show how the registers would store these denary values as 8-bit binary. Denary value 8-bit binary 46 171 [2] Working space … … … … (b) Give the largest denary value that can be stored in the 8-bit binary register. … [1] (c) The hockey club wants to increase the number of people that can watch each match to 2000. The 8-bit binary register may no longer be able to store the value. Give the smallest number of bits that can be used to store the denary value 2000. … [1] Working space … … … … (d) Electronic data about the final score for the match is transmitted to a central computer 30 kilometres away, using serial transmission. (i) Explain why serial transmission is more appropriate than parallel transmission in this scenario. … … … … … … [3] (ii) The data transmission is also half-duplex. Describe half-duplex data transmission. … … … … [2] (iii) The data transmission uses checksums. Describe how checksums are used to detect errors in data transmission. … … … … … … [3]

1(a) 1 mark each Denary Value 8-bit binary 46 0 0 1 0 1 1 1 0 171 1 0 1 0 1 0 1 1 2 1(b) − 255 1 1(c) − 11 1 1(d)(i) Any three from: − More accurate/reliable/efficient over long distances − Less chance of interference / cross talk − …that will skew / distort the data // less likely to get errors − Data will arrive in order − Serial is cheaper to purchase/install/maintain 3 1(d)(ii) − Transmission in both directions … − …not at the same time // asynchronous 2 1(d)(iii) Any three from: − Calculates a value from the bits/data (to be transferred) // by example/description − Value is appended to the bits/data − Value is transferred with the bits/data − Receiver recalculates the checksum − If both values are different error is detected // if both values are the same the transmission is successful 3 (a) To earn marks, you must correctly convert both denary values (46 and 171) into their 8-bit binary representations. (b) You need to state the largest denary value that can be represented by an 8-bit binary register, which is 255. (c) To score this mark, you must provide the smallest number of bits required to store the denary value 2000, which is 11 bits. (d)(i) You need to provide any three distinct advantages of serial data transmission, such as being more accurate, less prone to interference, or cheaper. (d)(ii) You must explain that half-duplex transmission allows data to be sent in both directions but not simultaneously. (d)(iii) To earn marks, you need to describe the process of checksum error checking, including calculating a value, appending it, transferring it, recalculating at the receiver, and detecting an error if values differ.

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 To earn marks for 1(a), you must correctly convert each denary value (167 and 214) into its 8-bit binary equivalent. For 1(b)(i), you need to state one valid similarity between an IP address and a MAC address, such as both identifying a device or being unique. For 1(b)(ii), you must provide two distinct differences between an IP address and a MAC address, like how they are assigned or their bit length.

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 (a) To earn marks, you must correctly provide the hexadecimal and 8-bit binary equivalent for each given denary value. (b) You need to state two distinct benefits, such as easier reading or error identification, that users gain from converting binary to hexadecimal. (c) You must identify three specific real-world uses of hexadecimal, like MAC addresses or IP addresses.

1 Greta has a computer that she uses for schoolwork and leisure. (a) The computer has the Media Access Control (MAC) address: 00:A0:C9:14:C8:29 (i) Tick (3) to show whether the MAC address is initially assigned to the computer by the network, the manufacturer or the user. Tick (3) Network Manufacturer User [1] (ii) The values in the MAC address are hexadecimal values. Convert the three given hexadecimal values into 8-bit binary. 14 … A0 … C9 … [3] Working space … … … (iii) Convert the two given hexadecimal values into denary. 29 … C8 … [2] Working space … … … (b) Greta stores data on several off-line storage devices, including an external hard disk drive (HDD), a USB flash memory drive and a compact disc (CD). (i) Identify the type of storage for each device. External HDD … USB flash memory drive … CD … [3] (ii) Describe the operation of a HDD and how it stores data. … … … … … … … … [4]

1(a)(i) − manufacturer 1 1(a)(ii) One mark per each correct binary value. − 00010100 − 10100000 − 11001001 3 1a(iii) One mark per each correct denary value. − 41 − 200 2 1(b)(i) − Magnetic − Solid state − Optical 3 1(b)(ii) Any four from: − It has platters − Platters/disk divided into tracks − Platter/disk is spun − Has a read/write arm that moves across storage media − Read/writes data using electromagnets − Uses magnetic fields to control magnetic dots of data − Magnetic field determines binary value 4

1 Binary is a number system that is used by computers. (a) Tick (3) one box to show whether binary is a base-2, base-10 or base-16 number system. Tick (3) Base-2 Base-10 Base-16 [1] (b) Hexadecimal and denary are number systems that can be used by programmers. Convert these four hexadecimal values into denary values. 09 … 10 … 28 … A1 … [4] Working space … … … … …

1(a) − Base-2 1 1(b) − 9 − 16 − 40 − 161 4 (a) To earn the mark, a student must tick the box next to 'Base-2'. (b) To earn the marks, a student must correctly convert all four hexadecimal values to their denary equivalents: 9, 16, 40, and 161.

Cambridge IGCSE Computer Science · 0478

IGCSE Computer Science (0478) Data representation past paper questions

Revise IGCSE Computer Science (0478) — 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.

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