##Higher Computing 2009
(b) Represent the decimal number –73 using 8 bit two’s complement.
01001001 = 73
10110111 = -73
State one advantage of Unicode when compared to ASCII.
Unicode stores more characters so can support special characters in of foreign languages.
(a) A disk editor is a common example of utility software. Describe one function of a disk editor.
(b) The bootstrap loader is part of the operating system. State the purpose of the bootstrap loader.
First thing loaded on boot: used to load the operating system at start-up
Disguise itself as other harmless files
More data can be stored in registers; it can be accessed from there more quickly
(a) State one possible software compatibility issue that might prevent the new software from running.
Unsupported by the operating system
(b) State one possible hardware compatibility issue that might prevent the new software from running.
Insufficient memory available
(a) Describe one difference between a peer-to-peer network and a client-server network.
P2P stores files on all computers; CS stores on one central server
(b) Describe one possible technical reason for choosing a client-server network over a peer-to-peer network.
Backups can be made from the server - easier
JPEGs are smaller, more compressed, so would be quicker to send
Explain how the iterative nature of the software development process is used in the production of software.
ADITDEM repeated; made then evaluated and corrected / perfected.
Defines a scope of work; details limits on cost to client
A program is being designed which generates a username using the following steps:
get user initial and surname
display the username
(a) Show how these steps could be represented using a graphical design notation.
| | |
| | display username
| create username
get initial and surname
(b) The username is created by joining the initial to the end of the surname, for example “CarrickE”.
Name the string operation used to create the username.
Explain why there is a need for scripting languages within applications.
It allows users to extend the features of a program, using plug-ins.
(a) Explain what is meant by the term “robustness”.
Can handle unexpected inputs
(b) Explain what is meant by the term “reliability”.
No design flaws; gives correct outputs
New hardware is developed and the program has to use it.
(a) Programmers may make use of a module library. State what is meant by the term “module library”.
A collection of small parts of software which can be called by the program. They are stored externally, sometimes part of the OS.
(b) The program may require a user-defined function. State what is meant by the term “user-defined function”.
Code written specifically for this program by the developers.
18 A palmtop computer has a processor with a 24 bit address bus, 32 bit data bus and 8 control lines. The palmtop computer accepts flash cards as additional storage.
(a) The processor receives a signal on an interrupt control line. Explain what happens when the processor receives this signal.
The current process is stopped, and the new state is passed to the processor so the registers can be refreshed and can move on to the new process.
(b) Calculate the maximum amount of memory that the palmtop computer can address. Express your answer in appropriate units. Show all working.
= 2^24 x 32 bits
(c) Data is to be transferred from the processor to main memory using a write operation. Describe how a processor would perform a write operation. Your answer should mention the buses or control lines used at each stage.
The address is placed in the address bus, and the data bus with the data, then the write function of the control bus is activated and the data is transferred to the address.
(d) A file created on the palmtop is to be stored on the flash card. The file management and input/output management functions of the palmtop’s operating system are used during the transfer. Describe one task carried out by each of these functions.
File management - locating the data to be written / read
I/O management - gives feedback to the palmtop on the interface if there are issues with the transfer
(e) The price of flash cards has decreased in recent years as their capacity has increased.
State one other recent trend in the development of flash cards.
SD cards are smaller (in size)
19 Pat has a wireless enabled laptop in his house. He uses this to illegally access his neighbour’s wireless network.
(a) Name the Act of Parliament that makes this network access illegal.
The Computer Misuse Act
(b) Pat’s computer has anti-virus software installed. One technique used by anti-virus software to detect a virus is virus signature recognition.
(i) Name one other virus detection technique
Using a checksum in possibly infected files
(ii) Describe how your named technique detects a virus.
Calculates the properties of the file and applies a data set to it, stores that data, then checks that it matches at a later time to ensure the file has not been changed.
(iii) Describe how a virus might use camouflage to avoid virus signature recognition.
Minor changes to the code that do not affect the result - different syntax
20 A network is configured as a star topology. It contains four computers and a switch.
(a) Draw a labelled diagram of this star topology. You should clearly show the location of the switch.
N N \ / N = node S / = channel / \ S = switch N N
(b) Describe one advantage of using a star topology compared to a bus topology.
In a star network, only one node will be affected. In a bus network, all nodes will be affected as there is one main line.
(c) Explain why using a switch rather than a hub may improve the performance of a network.
The switch directs data to specific nodes so if more efficient.
(d) Explain why the addition of a print server to a large network contributes to an improvement in network performance.
Using one printer for all of the clients will be more efficient.
(e) Developments in browser software have contributed to the increase in the use of networks. Describe two of these developments.
UX additions like tabs and, in Chrome as an example, the Omnibar for Search.
21 One function of an interface is to store data in transit between the computer and a peripheral.
(a) State one other function of an interface.
Voltage conversion, Analogue-digital conversion
(b)(i) Describe how data is transferred using a serial interface. You may include a diagram in your answer.
Data is sent down a single line, one bit after another.
(ii) Describe how data is transferred using a parallel interface. You may include a diagram in your answer.
The opposite of serial: multiple lines, so multiple bits at a time.
(c) State one advantage of a serial interface over a parallel interface.
The data remains in order over long distances - no errors.
22 NoTow is a company running a city centre car park. The company require software to control the operation of the car park. The software will have modules for actions such as ‘recognising a car is at a barrier’, ‘printing an entry ticket’ and ‘calculating ticket charge’.
(a) Name the most suitable type of programming language to implement this software. Explain your answer.
Event-driven as it can act upon the user's input
(b) The software is written using modules. Describe two benefits to the programmer of writing modular code.
More readable, easier to find errors as they exist in just one place in the source.
(c) After the software is written, testing is carried out.
(i) “Testing should be planned in advance with the creation of a test plan containing the test data to be used and the expected results.” State the aspect of testing being described here.
Predefined / systematic
(ii) “Testing should be as thorough and complete as possible covering every part of the program with all kinds of test data and testers.” State the aspect of testing being described here.
Comprehensive / complete
NoTow would like the software to calculate the number of cars on a particular day that spent more than three hours in the car park. The number of whole minutes each car is parked in the car park is stored in a list, as shown on the right.
(d) Use pseudocode to design an algorithm to carry out this calculation. 4 PS
Set gt3 = 0
For each entry
If the time > 180 then
gt3 = itself + 1
(e) The output from part (d) is turned into a percentage of the total number of cars using the car park in a day. This is stored in a variable called percent. Using a programming language with which you are familiar, show how to format the
output to two decimal places.
(f) Identify the type of maintenance used to add the module described in part (d). Justify your answer.
Adding a new feature is 'perfective'.
23 A cinema ticket system allows customers to select and pay for their own tickets.
The top level algorithm is:
1. Get ticket details
2. Calculate cost
3. Display cost and accept payment
The module CalculateCost uses the number of tickets and the category of ticket to calculate the total payment due.
(a) State the most suitable data type for the parameter called Cost.
(b) Parameters can either be passed by value or by reference.
(i) Identify one parameter that is passed by value to the module CalculateCost. Justify your answer.
Category - it isn't changed / returned by the function.
(ii) Identify one parameter that is passed by reference to the module CalculateCost. Justify your answer.
The cost is passed to the function, changed, then returned.
(c) A program may use local variables and global variables.
(i) What is the scope of a global variable?
It can be accessed by any part of the program - all of it
(ii) State two advantages of using parameter passing rather than global variables when programming. 2 KU
Data passing is more clear so the program is more readable, hence can be maintained more easily.
(d) State one reason why portability of software is an important factor for developers to consider.
The program can have an influence on a wider set of users - e.g. web apps are accessible from virtually any device.
(e) To calculate the total cost the program must check the category of each ticket against the four possible categories.
(i) The programmer decides to use a nested If. Explain why this is a more efficient method. 2 PS
The nested loops will find a true condition more quickly and stop, so will save processing power.
(ii) State one other multiple outcome selection statement that the programmer could have used.
A case statement
(f) The program will make use of a 1-D array.
(i) When creating, or declaring, a 1-D array for use in a program, a name must be given to the array.
State two other items that should be set when the array is created.
The type of data in the array (either explicitly, VB, or implicitly, JS) and the size of the array are declared.
(ii) Explain why it is a more efficient use of system resources to pass an array by reference rather than by value.
The array would be duplicated if sent by value.
(a) Ten years ago, VideoStream’s best selling product was their VS32 video capture card. Due to advances in video camera technology, the VS32 video capture card is no longer for sale.
(i) One of the main components of the video capture card is the DSP. Describe the role of the DSP.
The DPS can compress the video at a fast rate.
(ii) Describe the technological advance in video cameras that has resulted in the drop in sales of all video capture cards.
From analogue to digital; more popular as they're used to transfer to a PC; tech advances; price drops.
(b) Derek has bought VideoStream’s latest video camera that comes with free video editing software.
(i) Derek records a two minute video using 24-bit colour and a 1000 by 800 pixel frame size at 10 frames per second. Calculate the file size of the uncompressed video. Show all working and express your answer in appropriate units.
(ii) The settings in part (i) produced a poor quality video. Explain why the video is poor quality.
Low FPS, will seem choppy. Raise frame-rate to improve. 25fps is needed for smooth video.
Derek records several video clips and tries out the free video editing software. He loads the video clips and then uses two features of the video editing software to edit the video as shown below.
(iii) Name two features of the video editing software that Derek has used to edit the video.
Sequencing and transitioning
(c) The default format for saving video clips from all VideoStream’s products is AVI. AVI is an example of a container file. Explain why AVI is a “container file”.
It 'contains' several types of file (audio and video (images))
(d) MPEG is a compressed video file type. Describe how MPEG achieves compression.
iFrames allow unchanged data to be removed reducing file size. Each frame is a JPEG so is already compressed, too.
(a) Compare the use of a WYSIWYG editor and a text editor in producing the website, in terms of their demand on system resources.
WYSIWYG needs more RAM as it has to render graphics in real-time.
(b) As part of a graphic for the website, Harpreet scanned the image of an eye using 24-bit colour.
Describe how a scanner captures an image. Your answer must contain an appropriate level of technical detail.
Light is reflected off the surface of the paper and detected by a CCD as an analogue input. It's then transferred to the computer after being digitised by an ADC.
(c) After scanning, Harpreet scaled the eye and used image manipulation software to adjust the image.
(i) Name the feature of image manipulation software that Harpreet used to carry out the adjustment.
(ii) Explain how this feature is able to improve the image of the eye.
One pixel at a time, it takes the average of the surrounding pixels and creates pseudo pixels around it from the data which are then used to increase the resolution.
(iii) Name and describe a compression technique that would allow Harpreet to reduce the file size of the 24-bit colour eye without losing any image quality when it is decompressed.
RLE: allows blocks of the same colour to be represented together rather than separate values.
(d) Harpreet would like music to be playing in the background while each web page is being viewed. The music can either be stored as a MIDI file or a compressed MP3 file.
(i) Describe one way that the file size is reduced when saving a sound file as a compressed MP3 file.
Frequencies beyond the range of human hearing are removed.
(ii) State two advantages of storing the music for Harpreet’s web page using MIDI rather than MP3.
Smaller file size so can be downloaded more quickly.
(a) SVG is an example of a vector graphic file type. Name one other vector graphic file type.
(b) Explain why the above logo can be stored more efficiently as an SVG graphic than in the equivalent bitmap graphic.
Made up of simple components; can be saved as a smaller file using SVG as it just stores the attributes of the graphic.
(c) Choose one of the objects in the metro logo above and show how it would be represented in SVG code. Your answer should include the name of the object and at least two attributes.
(d) A small part of the SVG code for the logo is shown: rgb(0,0,255)
(i) State which colour is represented by this code.
(ii) The largest number that can be entered into the rgb instruction shown above is 255.
Calculate the bit depth of that object. Show all working.
log(2)256= 8 (per colour)
3*8 = 24 bits
(e) The logo was converted to 3D and a texture applied to it. Explain the term “texture” in relation to 3D graphics.
An image of a pattern used to fill the surface of an object.
(f) The logo was converted to a bit-map so it could be animated. Name a bit-map format that would be suitable for storing the animated logo.
512 Mb Data Storage
Voice Recording Function
Bluetooth & Firewire Enabled
(a) A multimedia presentation has to be designed and created for the launch of the latest version of the phone.
(i) State two elements that should be included in the design of a multimedia presentation.
storyboard / plan of layout
(ii) Describe two reasons why FoneSmart may wish to create the presentation in multimedia authoring software rather than presentation software.
They can customise the design of the UI. Events and animations can be more complex.
(b) The phone has a voice recording function. This allows the phone torecord the user’s voice using 8-bit mono sound at 22 kilohertz. The recording is then stored on a flash memory card.
(i) Calculate the file size of a 30 second voice recording. Express your answer in appropriate units. Show all working.
3081*22000 = 5280000 bits
(ii) Calculate how many of these 30 second voice recordings can be stored on a 512Mb flash card. Show all working.
512*1024 / 645 = 813KB
(ii) One of the advantages of using a flash card in the phone, rather than optical or magnetic storage, is its portability. Describe one other advantage of using a flash memory card in the phone compared to optical or magnetic storage.
Lower voltage draw so can be used in small devices.
(c) Voice recordings may be stored using either PCM or ADPCM.
(i) State one advantage of storing the recording using ADPCM
compared to PCM.
Smaller file size
(ii) Describe how ADPCM stores sound data.
Difference in amplitude is stored for a specific sample rate
(d) FoneSmart have received complaints that some voice recordings are unclear. The waveform of one of these recordings is shown on the right. Explain why this recording is unclear.
Clipping / saturation of the lowest and highest frequencies
(e) Music files can be transferred to the phone by connecting the phone directly to a computer using either Bluetooth or Firewire.
(i) State one advantage of using “Bluetooth” rather than “Firewire” for transferring music files to the phone.
(ii) State one disadvantage of using “Bluetooth” rather than “Firewire” for transferring music files to the phone.
Slower transfer speed
(f) Explain how this smartphone demonstrates convergence of technology.
Wow, it can play music; shows that functions are becoming available on just one device; no need for music players.
(g) FoneSmart are designing a new smartphone that will use holographic storage. This phone will have a larger storage capacity and a faster data transfer rate than previous phones.
(i) Explain how holographic storage achieves a very high storage capacity.
There are multiple layers of storage.
(ii)Explain how holographic storage achieves a very high data transfer rate.
They can be read parallelly.