What Is -90 Using 8 Bit Twos Compliment

Higher Computing – Revision for 2011 Perfect Paper Prelim - ANSWERS

1. What is -90 using 8 bit twos compliment? 10100110 2. What is 90 using 8 bit twos compliment? 01011010 3. Draw and label 4 different network topologies. Drawings of Bus, Ring, Star, Mesh. Must label a channel and a node 4. Which is the most robust topology and why? Mesh - In the event of channel failure, the data can be sent via a different path 5. Name 2 methods for storing text in a computer. ASCII, UNICODE 6. Describe 2 differences between the 2 methods you named above. ASCII uses 8 bits per char, UNICODE uses 16 bits. UNICODE can store more alphabets than ASCII 7. What is the purpose of the bootstrap loader? A program in ROM that locates and loads the operating system when the computer is turned on 8. What does MIPS measure that clock speed does not? MIPS shows the number of instructions that can be completed per second 9. Name 6 lines on the control bus. Read, write, interrupt, NMI, clock, reset 10.Describe 2 ways a virus could camouflage to avoid detection Encrypting signature, inserting dummy code, changing order of code, pretending to be a useful file 11.How is a vector image stored? A collection of objects each with their own properties (instructions) about how to draw them 12.A vector image contains 2 uncoloured rectangles. They are then coloured red and their line thickness is increased. What happens to the file size and why? No change in file size. The value for colour and line thickness is simply altered. 13.Which operating system function looks after RAM and which looks after saving and deleting? RAM – memory management. Saving and deleting – file management 14.Describe: Integer, Real, String and Boolean data types. Integer – whole number, Real – decimal, String – text, Boolean – True or False 15.Use an IF statement to give an example of using a Boolean. IF age >= 18 THEN canvote = True 16.Which document is used at the testing stage to make sure we have met the requirements? Software Specification 17.At which stage of development is a structured listing produced as an item of documentation?

Implementation 18.Name 3 design methodologies (2 graphical, 1 text). Pseudocode (text), Structure Diagram (graphical), Flowchart (graphical) 19.A password creator program asks you three questions. It then uses the first 3 letters of each answer to create your password. Eg:

Fruit Holiday Colour PASSWORD banana spain yellow banspayel

Write ONE line of code that will create the password and store it in a variable called PASSWORD. Password = mid$(fruit,1,3) & mid$(holiday,1,3) & mid$(colour,1,3) 20.A macro can be created in 2 ways. What are they? Recording user’s actions or programming with a scripting language 21.Give 2 features of declarative, procedural and event-driven languages. Declarative – uses facts and rule / can be search Procedural – start and end point / instructions in sequence / loops / variables Event-driven – no start and end point / order of instructions depends on user’s inputs / menus, buttons etc built in to the editor 22.A programmer has created a function (CALCAREA) to calculate the area of a circle. Show how this function could be used to store the answer in a variable called AREA. (note: do not write the function, call the function) Area = calcarea(radius) 23.What do we call testers who are not part of the company writing the code? Independent Test Group 24.Why is the software development process called iterative? Earlier stages of the process will be revisited in the light of new information 25.Which selection structure can often be used in place of lots of ELSE IF commands? CASE 26.What are 4 methods used to improve computer performance and explain what each does? Increase data bus width – more data fetched in each fetch execute cycle More registers in CPU – processor can access data without using fetch execute cycle Increase Cache Memory – using fast SRAM instead of the slower DRAM Add more RAM – reduces virtual memory that uses disk drives Install processors that are dual or quad core – increases throughput of instructions Faster access hard drive – less time waiting for saving or loading Install faster interfaces – data can transfer between devices in less time 27.What eventually happens to a processor if you continue to increase the clock speed it is working at? Overheats

28.A computer system has a 3GHz processor, 8 bit control bus, 48 bit data bus and 32 bit address bus. What is the maximum addressable RAM? 2^32 * 48 = 24 GB 29.What status signals would be passed between the processor and a peripheral that had interrupted it? Condition of peripheral (ready, out of paper etc) Data received 30.Data is to be transferred from the RAM to the processor using a memory READ operation. Describe how this would happen (mention buses, registers etc). MAR sends address to address bus Address bus activates RAM location Control Unit activates Read line of control bus Data can now be passed onto Data bus Data is received from Data bus into MDR 31.Describe the MIPS, FLOPS and application based tests of computer performance. MIPS – counts number of instructions the processor can complete in 1 second FLOPS – counts number of floating point operations the processor can complete in 1 second Application based – measures time taken to complete ‘real life’ practical tasks 32.Which of the above tests gives an indication of the ‘real world’ performance of a computer? Application based 33.Which part of the computer does FLOPS test thoroughly? Measures processing power but not all other parts of the computer 34.Status signals are messages. What are they sent between and what information do they carry? Sent between CPU and peripheral. Signals indicate if devices are ready to send or receive data. Confirm if data has been received. 35.Interfaces can be serial or parallel. Give an advantage of each. Draw a diagram to show how each sends data. Serial – no skewing so can be longer distance. Parallel – many wires at same time so faster 36.Describe 2 roles of the systems analyst and 2 roles of the project manager. Systems Analyst – investigates current system / observes workplace / sends questionnaires / creates specification Project manager – sets deadlines / monitors costs 37.What do we call the process of breaking a large problem into smaller problems and repeating this until each task is easily understood and coded? Stepwise refinement

38.Give 2 reasons why it is essential to start the software design process by analysing the problem. The specification produced is an important legal document / this stage makes sure all future stages are appropriate / without this stage the final program may not be what was needed 39.A smart phone App is being developed to store an amount every time you spend some money and tell you the total at the end of the week. What data structure and type is needed to store the data? Array / Real 40.Write an algorithm in pseudocode that will find the largest amount spent in the above App. Set max to spent(1) For each item If current value > max Set max to current value End if Next item Display max 41.What do we call pre-written and pre-tested subroutines used in the development of software? Module library 42.What do we call a variable that has a scope of only one module? Local 43.What 2 advantages does the above type of variable have? Variables cannot be accidentally altered by other modules Program more readable / maintainable Aids modularity (the modules can easily work in other programs) 44.Define the following network hardware: hub / switch / router Hub – a ‘simple’ device to join computers together in a LAN – sends data to all nodes Switch – a ‘clever’ device to join computers together in a LAN – only sends the data to the correct node Router – joins networks together – eg joins your LAN to the Internet 45.Describe 2 methods of improving transmission speeds on a network. Use network cards with higher bandwidth Replace hubs with switches Use cabling with higher bandwidth (eg fibre optic) 46.Compare the roles of a file server and a web server. File server is a central storage location for files on a network. It manages the security of files and allows sharing. Web server allows creation of private internal website and / or public external website. Caches web pages locally for faster access 47.Give an advantage and a disadvantage of developing software with a scripting language compared to starting from scratch with a high level language.

Advantage of scripting language – develop applications within the existing software (not starting from scratch) / allows automation of frequently used commands Disadvantage of scripting language – final product may not be fully customised to needs 48.Describe 2 security risks that may arise after connecting your office network to the internet. Attack from hackers / Viruses spreading / Malware (pop-ups, keyloggers…) 49.Give 2 advantages of a client / server network compared to a peer to peer network. Advantage – centralised backups / can implement security levels / remote updates and repairs 50.Give 2 similarities and 2 differences between procedural and event-driven languages. Similarities – range of data types / loops and condition commands / modular Differences – interface (event-driven has buttons etc built in), order (event-driven’s order can change depending on user’s inputs), start and end point (event-driven has no start and end point) 51.Would you use a procedural, declarative or event driven language to make an interactive computer game and give 1 reason why? Event-driven – the order of a game depends on the users inputs and events that happen during the game. Can provide a graphical interface to activate events. 52.Computer games and applications should be as portable as possible. Why is this? Customers have different platforms therefore it is important that the game can be released for different platforms with few modifications.