9608_w18_qp_12
A paper of Computer Science, 9608
Questions:
6
Year:
2018
Paper:
1
Variant:
2
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1
A company is designing a website. The company creates a 4-colour bitmap image for the website as shown. Each colour is represented by a letter, for example, G = grey, K = black. G G G G G W R R R R G W G G G G G W K K K K K W W W W W K K R R R R R R State the minimum number of bits needed to represent each pixel in the image in part . Calculate the minimum file size of the image shown in part . Show your working. Working File size The company takes a photograph of their office to put on the website. The photograph has a resolution of 1000 pixels by 1000 pixels. Two bytes per pixel are used to represent the colours. Estimate the file size of the photograph in megabytes. Show your working. Working Estimated file size The file size of the photograph needs to be reduced before it is placed on the website. Draw lines to link each method of reducing the file size of the image to: • its description and • its compression type, where appropriate. Description Method Compression type Removes pixels Reduces number of pixels per inch Uses fewer bits per pixel Stores colour code and count of repetitions Crop the photograph Use run-length encoding Use fewer colours Lossy Lossless The company has created a logo for the website. The logo is a vector graphic. Describe two reasons why a vector graphic is a sensible choice for the logo. Reason 1 Reason 2
1. Theory Fundamentals  →  1.1. Information representation
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2
Gopal types the Uniform Resource Locator (URL) of a website into a web browser. The following sequence (1 to 5) describes the steps that take place. There are three missing statements. Gopal types into the web browser. DNS looks up the URL in table Three statements A, B and C are used to complete the sequence. A DNS finds corresponding IP address B Web browser sends URL to Domain Name Service (DNS) C DNS returns IP address to web browser Write one of the letters A to C in the appropriate rows (2, 4 and 5) to complete the sequence. Describe the purpose of an IP address. A telecommunications operator has installed fibre-optic cables in Gopal’s neighbourhood. Give three benefits of fibre-optic cable over copper cable. Give two drawbacks of fibre-optic cable over copper cable.
1. Theory Fundamentals  →  1.2. Communication and Internet technologies
Open
3
The following table shows assembly language instructions for a processor which has one general purpose register, the Accumulator (ACC) and an Index Register (. Instruction Explanation Op code Operand LDD Direct addressing. Load the contents of the location at the given address to ACC. LDX Indexed addressing. Form the address from + the contents of the Index Register. Copy the contents of this calculated address to ACC. LDR #n Immediate addressing. Load the number n to IX. STO Store contents of ACC at the given address. ADD Add the contents of the given address to ACC. INC Add 1 to the contents of the register (ACC or . DEC Subtract 1 from the contents of the register (ACC or . CMP Compare contents of ACC with contents of . JPE Following compare instruction, jump to if the compare was True. JPN Following compare instruction, jump to if the compare was False. JMP Jump to the given address. OUT Output to the screen the character whose ASCII value is stored in ACC. END Return control to the operating system. State what is meant by absolute addressing and symbolic addressing. Absolute addressing Symbolic addressing Give an example of an ADD instruction using both absolute addressing and symbolic addressing. Absolute addressing Symbolic addressing State what is meant by indexed addressing and immediate addressing. Indexed addressing Immediate addressing Give an example of an instruction that uses: Indexed addressing Immediate addressing The current contents of a general purpose register (are: X The contents of X represent an unsigned binary integer. Convert the value in X into denary. The contents of X represent an unsigned binary integer. Convert the value in X into hexadecimal. The contents of X represent a two’s complement binary integer. Convert the value in X into denary. The current contents of the main memory, Index Register (and selected values from the ASCII character set are: Address Instruction ASCII code table (selected codes only) LDD 100 ASCII code Character CMP 104 / JPE 54 * LDX 100 - CMP 105 + JPN 47 ^ OUT = LDD 100 DEC ACC STO 100 INC IX JMP 41 END … IX This is a copy of the instruction set. Instruction Explanation Op code Operand LDD Direct addressing. Load the contents of the location at the given address to ACC. LDX Indexed addressing. Form the address from + the contents of the Index Register. Copy the contents of this calculated address to ACC. LDR #n Immediate addressing. Load the number n to IX. STO Store contents of ACC at the given address. ADD Add the contents of the given address to ACC. INC Add 1 to the contents of the register (ACC or . DEC Subtract 1 from the contents of the register (ACC or . CMP Compare contents of ACC with contents of . JPE Following a compare instruction, jump to if the compare was True. JPN Following a compare instruction, jump to if the compare was False. JMP Jump to the given address. OUT Output to the screen the character whose ASCII value is stored in ACC. END Return control to the operating system.
1. Theory Fundamentals  →  1.4. Processor fundamentals
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4
A student has written the steps of the fetch stage of the fetch-execute (FE) cycle in register transfer notation. The student has made some errors. Line 1 MDR [PC] Line 2 PC PC + 1 Line 3 MDR [MAR] Line 4 CIR PC Identify the line numbers of three errors that the student has made. Write the correct notation for each error. Line number of error Correct notation One stage of the FE cycle includes checking for interrupts. Give three different events that can generate an interrupt. Explain how interrupts are handled during the fetch-execute cycle. The processor uses buses in the FE cycle. The diagram shows three buses and two descriptions. Draw one line from each bus to its appropriate description. Bus Description Control bus Address bus Data bus Unidirectional (one direction) Bidirectional (two directions)
1. Theory Fundamentals  →  1.4. Processor fundamentals
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5
This question presents three scenarios. For each scenario, tick (✓) one box to show whether you think the person’s behaviour is ethical or unethical. Justify your choice. Wendy is a software engineer who is developing a program for her company. Her friend, Noah, is developing a program for a different company. Wendy looks at the code that Noah is writing to get ideas for her own program. Ethical Unethical Justification Amit is fixing some bugs in the computer system of a large multinational company. He is asked to sign a confidentiality agreement. He sees some confidential information which contains the names of other multinational companies that have broken the law. He copies this information and releases it on the Internet. Ethical Unethical Justification Farah is providing a company with an estimate for the cost of writing a program. The company she works for is in financial difficulty so she increases the estimate by 10%. Ethical Unethical Justification
1. Theory Fundamentals  →  1.7. Ethics and ownership
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6
Kim is using her laptop computer to write a program in a high-level language. Kim needs to make sure the program is secure against unauthorised access. She has already set up a username and password on her laptop. Identify two additional electronic measures that Kim can use to keep the program secure. Kim will use library routines in her program. Describe what is meant by a library routine. Describe one benefit and one drawback of using library routines. Benefit Drawback Kim develops her program and makes it ready for use. To do this, she uses first an interpreter and then a compiler. Explain why Kim needs to use both an interpreter and a compiler. Interpreter Compiler
1. Theory Fundamentals  →  1.5. System software
3. Advanced Theory  →  3.4. System software
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