Computer Science Paper 12

Any two from:

– direct access to computer processor / special hardware // machine dependent instructions – uses up less memory – can increase the speed of processing a program // executes instructions faster [2]

Statements Interpreter (9)

Compiler (9)

Translates the source code into machine code all at once 9 Produces an executable file in machine code 9 Executes a high-level language program one instruction at a time 9 Once translated, the translator does not need to be present for the program to run 9 An executable file is produced 9 [5]

Any two from:

serial – one bit sent at a time // bits sent sequentially – over a single wire – synchronous or asynchronous [2]

Any two from:

parallel – several bits / a byte sent at a time – using many / multiple wires – synchronous [2]

– serial Any two from:

– serial data transmission more reliable over long distances – less likely for the data to be skewed/out of synchronisation – less interference as only a single wire – it is a cheaper connection as only single wire needed // cheaper to set up – a fast connection is not required as a printer is limited by its printing speed [3]

Intersection of Row 7 and column 4 circled [1]

– Row (byte number) 7 has an odd number of 1s (five 1s) – Column (bit number) 4 has an odd number of 1s (five 1s) [2]

112 [1]

56 [1]

divided by 2 // value 112 was halved // multiplied by 0.5 [1]

0 0 0 0 1 1 1 0 [1]

14 [1]

Any two from:

– run out of places to the right of register / at the end of register – right-most 1 would be lost – number would become 3 instead of 3.5 – loss of precision [2]

0 0 0 0 1 1 1 0

2 marks for 4 correct outputs, 1 mark for 2 correct outputs 1 mark for correct gate AND gate [3]

2 marks for 4 correct outputs 1 mark for 2 correct outputs 1 mark for correct gate OR gate [3]

A B Working space X 0 0 0 0 1 0 1 0 0 1 1 1 A B Working space X 0 0 0 0 1 1 1 0 1 1 1 1

1 mark per correct section. [4]

4 marks for 8 correct outputs 3 marks for 6 correct outputs 2 marks for 4 correct outputs 1 mark for 2 correct outputs [4]

A B C Working space X 0 0 0 0 0 0 1 1 0 1 0 0 0 1 1 0 1 0 0 0 1 0 1 1 1 1 0 1 1 1 1 1 1 mark 1 mark 1 mark 1 mark

Any two from:

– a large number of requests are sent to the network/server all at once – designed to flood a network/server with useless traffic/requests – the network/server will come to a halt/stop trying to deal with all the traffic/requests – prevents users from gaining access to a website/server [2]

1 mark for each security threat and 1 mark for matching description Security threat Description Viruses – software that replicates – causes loss/corruption of data // computer may “crash”/run slow Hacking/cracking – illegal/ unauthorised access to a system/data Phishing – a link/attachment sends user to fake website (where personal data may be obtained) Pharming – malicious code installed on user’s hard drive / computer – user is redirected to a fake website (where personal data may be obtained) Spyware/key logger – send/relay key strokes to a third party [4]

Any three from:

– hyper text mark-up language – uses both structure and presentation – web-authoring language/software // used to create websites/webpages – uses tags to define e.g. colour / font / graphics / layout [3]

File name: ComputerSciencePapers Protocol: http(://) Web server name: www.cie.org.uk [3]

1 mark per nibble 0010 1010 1111 [3]

1 mark for identification of each sensor, max 2 for each description Infrared/motion sensor – Receives infrared rays/heat – Sends data to microprocessor – Receives microwaves – Placed in the corner of a room, across a doorway – Used to detect the heat of an intruder // used to detect if an infrared beam has been broken by an intruder Pressure sensor – Receives current if circuit created // stops receiving current if circuit is broken – Sends data to microprocessor – Placed on a window/door, at the entrance – Used to detect a change in pressure [6]