Published on March 6th 2025 | 17 mins , 3332 words
451/1
COMPUTER STUDIES
PAPER 1
MARKING SCHEME
SECTION A (40MARKS)
1. Two practices that ensure the safety of the computer user
- All cables should be insulated
- Cables should be laid away from user pathways.
- Providing standard furniture
- Use antiglare screens on CRT monitors
- Avoid overcrowding of computers and users.
- Adjust the display lighting.
(First 2x1)
2. Definition of portability as used in software selection
- Ability of a software to be copied or installed in more than one computer.
(first 1x1)
3. a) How OS manage computer memory
- OS manage the memory by organizing it into blocks of sizes called page frames. Task are equally divided into pieces that can fit into the frames.
- OS swaps the tasks between the main memory and the virtual memory on the hard disk.
(first 1x2)
b) i) What is meant by disk partitioning?
- Process of diving a large physical disk into two or more partitions called logical drives.
(First 1x1)
ii) Purpose of disk partitioning
- For the purpose of installing more than one OS on the same disk.
- For the purpose of backup on the same disk but different partitions.
(first 1x1)
4. a) Four stages in data processing cycle
- Data collection
- Data input
- Data processing
- Data output
(In correct sequence) (first 4x ½ )
b) i) Reference file
- A file that contain data used for lookup purposes e.g. price list. (first 1x1)
ii) Master file
- Contains relatively permanent data (first 1x1)
5. a)
- Body scanners will replace security guards by scanning travellers as they enter to detect prohibited items.
- Online booking will replace clerks at booking offices
- Payments using plastic cards (electronic) will replace receipt inspectors and conductors.
(first 2x1)
b) One role of:
i) Webmaster
- Develop websites for organization and individuals
- Install web pages information
- Maintain, update and modify information on webpages.
(first 1x1)
ii) Network administrator
- Controls and monitors Network resource usage
- Sets up a computer network
- Maintain and troubleshoot network related problems
- Maintain and enforce network security measures.
(first 1x1)
6. a) One reasons why parallel cables are faster than serial cables in data transmission
- Parallel cables transmit many bits of data simultaneously using set of conductors while serial cables transmit only one bit at time. (first 1x1)
b) Two ways that may be used to represent a negative number in a number
- Ones complements
- Twos complement
- Prefixing an extra sign bit
(first 2x1)
7. a) Distinguish between autocomplete and the autocorrect feature
- Autocomplete is a feature that automatically displays a complete word when the user types the first few characters.
- Autocorrect is a feature that automatically detects wrongly capitalized or spelt word and replaces it with the correct one.
(first 1x2)
b) What is thesaurus?
- A tool that helps the user find words or phrases with similar meaning or opposite meaning to the one selected (first 1x1)
8. Definition of:
i) Internet
- Interconnection of computer networks globally to facilitate flow of information world widely. (first 1x1)
ii) Piconet - A network of bluetooth enabled devices.
- A device / software that enable Bluetooth – enabled devices to communicate. (first 1x1)
9. Reasons why DTP is preferred over word processors
- Items can be edited independently since every item on a page is contained in a frame.
- Frames need not to flow in logical sequence e.g. a story on pages I can be continued on page 5.
- DTP has a wide range of templates that can be used to create a document first
- Master pages are used to set a common layout which may be repeated on several pages. (first 2x1)
10. Symbols of some keyboard keys:
4 x ½ = 2 mks
11. Factors to consider when buying input devices
- Initial cost of the input device
- Volume of data to be input (Speed of the device)
- Reliability of the device
- Mode of operation
- Appropriateness of the device.
(first 4x1)
12. a) Distinguish between workbook and a worksheet
i) - Workbook – An excel file that consists of several worksheet
- Workbook – a group of worksheets
ii) Worksheet – a work area made up of rows and columns into which data is entered. (1x2)
b) Meaning of “what if analysis”
- A feature used to predict / forecast an outcome if a value used in a formula or function are changed. (1x1)
13. Reason why HTML is not considered as a true programming language
- HTML does not have declaration part and control structures (first 1x1)
14. Definition of:
i) Piracy – Illegal copying of copyrighted software. (First 1x1)
ii) Industrial espionage
- Involves spying on a competitor to get information that can be used to cripple the competitor. (First 1x1)
15. Types of relationships as used in database design
3 x 1 = 3 marks
SECTION B (60marks)
16.
a)
i) i) A = 2
B = 4
Y = 2+4 = 6 ü (1mark)
Y = 6
ii) A = 4
B = 6
Y = 10 ü (1mark)
iii) A = 6
B = 10
Y = 16 ü (1mark)
iv) A = 10
B = 16
Y = 26 ü (1mark)
ii) Control structures
- Sequence
- Loop / iteration / while….do (First 2x1)
b)
c) Examples of iteration construct
- WHILE – DO
- FOR
- Repeat until
(First 3x1)
17. a)
i) Satellite transmission system (First 1x1)
ii) A – Earth station / transmitter
B – Satellite in the space
C – Uplink
D – Downlink (1x4)
iii) Advantages of satellite transmission
- Cover a wide geographical area
- Low attenuation rate.
- Flexible
(3x1)
b) i) Network topology
- Physical arrangement of computers and other devices on a network.
(1x1)
ii) Distinguish between logical and physical network topology
Logical – the way devices communicate
Physical – the physical arrangement of devices in a network
(2x1)
c) i) Network Interface Card (NIC)
- A device that creates a physical link between a computer and the Network. (1x1)
ii) Gateway – A computer or device that connects networks with different protocols or internet (1x1)
iii) Bridge – A device that divides a network into segments.
iv) Repeater – a device that receives a weak signal, cleans, amplifies it and the retransmit (1x1)
18. a)
- New opportunities – new technology/ a chance to improve services.
- Problems – undesired situations that prevent the organization from meeting its goals.
- Directives from the management or government. (First 3x1)
b)
- Improvement in technology
- Change in user requirement
- New management policies
(3x1)
c)
- Flowcharts
- Pseudcodes
- Data flow diagrams
(First 2x½ )
e) Advantages of questionnaire over interview
- Where sincere responses are required
- Where responses are not urgent
- When the area to be covered is large (geographically) and respondents are scattered
(First 2x1)
f) Reasons why users may resist introduction of information system in place of work
- Fear of losing job
- Fear of being displaced by computer literate people
- Fear of side effects on their health.
(First 3x1)
19. a) i) 113.2510 = X2
| 2 | 113 | Rem
| 2 | 56 | 1
| 2 | 28 | 0
| 2 | 14 | 0
| 2 | 7 | 0
| 2 | 3 | 1
| 2 | 1 | 1
| 2 | 0 | 1
11310 = 11100012ü1
0.25 x 2 = 0.5
0.5 x 2 = 1.0
0.2510 = 0.012ü1
x2 = 1110001.012ü1
ii) 1001110.100112 = x10
1 0 0 1 1 1 0
26 25 24 23 22 21 20
64 32 16 8 4 2 1
64 + 8 + 4 + 2
= 7810ü1
0. 1 0 0 1 1
2-1 2-2 2-3 2-4 2-5
0.5 + 0.0625 + 0.03125
= 0.5937510ü1
x10 = 78.5937510ü1
b) Using two’s complement
i) 5710 – 2910
5710 = 1110012
2910 = 111012
Ones complement of 0111012 = 1000102ü1
Twos complement = 1000102 + 12
= 1000112ü1
111001
100011
(1)011100 = 111002ü1
c) BCD equivalent of 3710
3 = 00112 ü1
7 = 01112ü1
3710 = 001101112ü1
20. a) Virtual reality:
- A condition in which a person becomes psychologically immersed in a artificial environment generated by a computer. (2x1) = 2
b) i) Headgear
- A device with tiny screens worn on the head, enable the weaver to view the virtual world.
ii) Body suit
Worn by the user, enable the wearer to explorer the virtual world
c) i) Artificial intelligence
- Science of designing machines that mimic the intelligence of a human (2x1) = 2
ii) Components of expert system
i) User interface – set of software that link computer expert system and its user.
ii) Knowledge base – a database of knowledge of an experts system.
iii) Inference engine – software that applies the rulers from a knowledge base to the data provided by the user to draw conclusion.
(3x2) = 6
d) Physical features of human beings that can be considered in biometric analysis
- Finger prints
- Voice recognition
- Eye / facial recognition.
(First 3x1)