Computer Science Paper 12
May / June 2016·2210·11 questions
Mock exam: 105 min, official timing
Question paper
Question 1
Question 2
Question 3
Question 4
Question 5
Question 6
Question 7
Question 8
Question 9
Question 10
Question 11
Mark scheme
Question 1
compiler assembler interpreter [3]
Question 2
Application Sensor controlling street lights Light monitoring a river for pollution Gas, pH, temperature, light controlling traffic lights pressure, magnetic field, NOTE: The same sensor cannot be given twice [3]
Question 3
3(a)[3]
1 mark for each nibble 0100 1010 1111 [3]
3(b)(i)[3]
0 1 1 0 1 0 0 1 105 hours 1 mark 0 0 0 1 1 1 1 1 31 minutes 1 mark 0 0 1 1 0 0 1 0 50 seconds 1 mark [3]
3(b)(ii)[1]
1F [1]
Question 4
4(a)[3]
Any three from:
– The file can be compressed – The compression that is used is lossless (not lossy) – use of a compression algorithm – repeated words can be indexed – repeated word sections (e.g. “OU”) can be replaced by a numerical value – reference to zip files – save file as a pdf/convert to pdf [3]
4(b)[4]
Any four from:
– the checksum for the bytes is calculated – this value is then transmitted with the block of data – at the receiving end, the checksum is re-calculated from the block of data received – the calculated value is then compared to the checksum transmitted – if they are the same value, then the data was transmitted without any error – if the values are different, then an error has been found – if the values are different, then a request is sent for the data to be re-transmitted [4]
Question 5
Description Device Allows a user to write on a surface using a pen;
text and drawings are then captured electronically and stored for later use. Digital Light Projector Converts sound into an electrical signal/voltage. Inkjet printer Uses thermal bubble and piezoelectric technology to produce a hard copy. Interactive whiteboard Uses a bright white light source and micro mirrors (on a chip) to produce an image to be shone onto a wall or screen. Laser printer Converts a hard copy document into an electronic form to be stored as a file on a computer. Microphone Uses negatively charged images on a rotating drum and positively charged toner to output a hard copy. Scanner (2D) 5/6 matches – 5 marks 4 matches – 4 marks 3 matches – 3 marks 2 matches – 2 marks 1 match – 1 mark [5]
Question 6
6(a)[6]
Type Tick (✓) Method Tick (✓) simplex serial half-duplex parallel ✓ full-duplex → Type Tick (✓) Method Tick (✓) simplex ✓ serial ✓ half-duplex parallel full-duplex Type Tick (✓) Method Tick (✓) simplex serial ✓ half-duplex ✓ parallel full-duplex [6]
6(b)[2]
Any two from:
– single wire means there is less chance of interference/data corruption – single wire reduces costs – more reliable over greater distances – bits will still be synchronised after transmission [2]
Question 7
7(a)[4]
A B C Working space X 0 0 0 0 0 0 1 1 0 1 0 0 0 1 1 1 1 0 0 0 1 0 1 1 1 1 0 1 1 1 1 0 4 marks for 8 correct X bits 3 marks for 6 correct X bits 2 marks for 4 correct X bits 1 mark for 2 correct X bits [4]
7(b)[5]
1 mark for each correct gate with correct source of input [5]
7(c)[4]
Each dotted area is 1 mark [4]
A B C X A C B X
Question 8
8(a)[3]
1 mark for correct lines from each type of software NOTE: all statements that are correct must be connected to the correct type of software for the mark to be awarded Statement Type of software Users have the freedom to pass on the software to friends and family as they wish. Free software Users can download this software free of charge, but they cannot modify the source code in any way. Users are allowed to try out the software for a trial period only before being charged. Freeware Users can study the software source code and modify it, where necessary, to meet their own needs, without breaking copyright laws. Shareware Users can obtain a free trial version of the software, but this often does not contain all the features of the full version. [3]
8(b)[3]
Any three from:
– That we should follow Copyright laws/intellectual property rights/work should not be stolen/plagiarised – That we should follow Data Protection laws – That we should not create or distribute malware//description of malware – That we should not hack/crack other computers//description of hacking – That we should protect our own computers against malware/hacking – That we should consider privacy issues (when using social networking) – That we consider anonymity issues (when using social networking) – That we should consider environmental impacts when using computers – Loss/creation of jobs from use of computers/robotics – We should follow codes of practice (for creation of code e.g. ACM/IEEE) [3]
8(c)[6]
2 marks for each term described Viruses: – program/software/file that replicates (copies) itself – intends to delete or corrupt files//fill up hard disk space Pharming: – malicious code stored on a computer/web server – redirects user to fake website to steal user data Spyware: – monitors and relays user activity e.g. key presses//key logging software – user activity/key presses can be analysed to find sensitive data e.g. passwords [6]
8(d)[3]
Any three from:
– examines/monitors traffic to and from a user’s computer and a network/Internet – checks whether incoming and outgoing traffic meets a given set of criteria/rules – firewall blocks/filters traffic that doesn’t meet the criteria/rules – logs all incoming and outgoing traffic – can prevent viruses or hackers gaining access – blocks/filters access to specified IP addresses/websites – warns users of attempts by software (in their computer) trying to access external data sources (e.g. updating of software) etc. // warns of attempted unauthorised access to the system [3]
Question 9
9(a)[2]
Binary number A: 1 1 1 0 0 1 0 Binary number B: 1 0 0 1 1 1 0 [2]
9(b)[2]
Parity Bit Binary number A 1 Binary number B 1 [2]
Question 10
1 mark for each correct storage device ROM (not EPROM/PROM) Blu-ray disc RAM DVD/ DVD-R(+R)/ DVD-RW(+RW)/ DVD-ROM (not CD or DVD-RAM) SSD/example of a USB storage device DVD-RAM [6]
Question 11
1 mark for each correct point – Presentation is used to format colour/style – Structure is used to create layout – In a HTML document structure and presentation are often kept separate – By keeping the presentation separate it is easier to update colour/font – Presentation is often stored in a file called a CSS … – … the CSS in then linked to the HTML document to implement the presentation requirements – (Mark-up) tags are used to define the structure of the document … – … presentation and formatting can also be included within the tags [4]