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COMPUTER STUDIES 2024

PAPER 1
MARKING SCHEME
SECTION A (40 Marks)
1. Give TWO reasons why Powder type fire extinguishers are not recommended to be used in
a computer laboratory.
i. Powder based fire extinguishers may react with some electrical components hence
changing their electrical characteristics
ii. Powder based fire extinguishers has abbrasive particles that may cause corrosion to
moving parts of the computer
Or any other correct responce
Reason @ 1 Mark
Total = 2 X 1 Mark
= 2 Marks

2. State the purpose of each of the following memories in a computer system.

(i) ROM
It stores the firmware that is required frequently to perform specialised functions on
the computer ie to control the booting process
Or
It is used to permanently hold information that can only be accessed but not modified
or erased by the user

(ii) RAM
Temporarily holding
a. User data
b. Running programs
c. Input storage shortly before processing
d. Output storage shortly after processing
Or any other correct responce
Purpose @ 1 Mark
Total = 2 X 1 Mark
= 2 Marks

3. State two factors that one would consider when selecting data entry method in computing.

i. Type of data
ii. Speed of input device

Or any other correct responce

Factor @ 1 Mark

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 Total = 2 X 1 Mark
= 2 Marks
4. Describe the following types of printers and state one application area of each.
(a) Dot matrix
A dot-matrix printer is an impact printer that produces printed images with a print
head striking mechanism. The print head of a dot matrix printer is implemented in an
array of pins arranged in rows and columns. To print a character, the required sets
of pins are activated and sruck against an inked ribbon leaving the image on paper.
Application – in banks for printing bank slips

(b) Thermal printer.

It is a non impact printer that uses a chemically treated paper that changes color to
form characters when subjected to heat. Application – in photo studios to print
pictures
Description @ 1 Mark
Application Area @ ½ Mark
Total = (2 X 1 Mark) + (2 X ½ Mark)
= 3 Marks

5. Differentiate between in-house software and freeware.

These are programs developed and designed to solve specific user problems. They are
developed for a specific person/ organisation and therefore they cannot be used by
anyone else except the owners of the software who have all the rights over the software
while freeware software are software products that are freely made available to the user.
Most freeware software are distributed freely over the internet where the user can
download a program of choice.
Difference @ 2 Marks

6. Give two importance of feedback mechanism in systems

i. The feedback mechanism helps in evaluating the system output to determine whether
a system is moving toward the achievement of its goal
ii. The feedback mechanism helps in monitoring the performance of the system

Or any other correct responce

Importance @ 1 Mark
Total = 2 X 1 Mark
= 2 Marks

7. With an aid of a diagram, explain one-to-one database relationship.

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PRESIDENT LE COUNTRY
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 A one-to-one relationship is created if and only if the relating field in both tables are
primary keys
Diagram @ 1 Mark
Explanation @ 1 Mark
Total = (1 X 1 Mark) + (1X 1 Mark)
= 2 Marks

8. KASSU Secondary School intends to set up internet connection in their school for e-learning
purposes. Advise the school management on four internet connectivity requirements that is
required for them to be able to access internet.
i. Network interface card
ii. Internet service provider
iii. Computer
iv. Communication media
Or any other correct responce
Connectivity requirement @ ½ Mark
Total = 4 X ½ Mark
= 2 Marks

9. The figure below shows an extract of an e-mail application.

What is meant by each of the following terms:

(a) Trash
Acts as a dust bin for your e-mail account where all deleted mails are stored
before being permanently removed from the account

(b) Spam
This is a folder in your account where all junk and suspicious mails received are
stored

(c) Inbox
This is a folder in your account where all genuine mails received are stored
Meanimg @ 1 Mark

3
 Total = 3 X 1 Mark
= 3 Marks

10. State two ways in which users in an organization can be a security threat to data in an
information system.
i. Through accidental access to files they are not supposed to access
ii. By using confidential data for their own personal gain
iii. Through intentional access to unauthorised data
Or any other correct responce
Threat @ 1 Mark
Total = 2 X 1 Mark
= 2 Marks

11. State three negative impact of information communication technology on the Environment.
i. The huge garbage dumps of dead computer parts, printers, ink toners, cartridges,
monitors and other accessories are deposited in land fills causing pollution.
ii. Disposal of Nickel-Cadmium laptop batteries which contain toxic cadmium are
buried in a land fill can leak into underground water table and catchment areas.
iii. Massive extraction of natural resourses such as mining of iron ore and other metals
for the costruction of computer parts
Or any other correct responce
Threat @ 1 Mark
Total = 3 X 1 Mark
= 3 Marks

12. In a computer based information system, state the purpose of the following files and give
one example where such a file may be required in a school.
a. Report file.
A report file is used to extract records from the masterfile or generated after
processing. It stores a copy of the generated reports by the system.

b. Sort file.
A sort file is used where data is to be processed sequetially to first arrange the
records in the order of the master file before updating it. Example students exams
marks entered in a class list
Function @ 2 Marks
Total = 2 X 2 Mark
= 2 Marks

13. State three responsibility of a Database administrator in an organization.

i. Selection of hardware and software
ii. Managing data security and privacy
iii. Managing Data Integrity

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 iv. Data backup
v. Database recovery
vi. Tuning database performance
vii. Improving query processing performance

Any three correct responce

Responsibility @ 1 Mark
Total = 3 X 1 Mark
= 3 Marks

14. With an example for each, describe how computers are used in the following areas of
education;
a. Simulation
This is whereby the compters are designed to resemble the actual enviroment for
the users to learn instead of going to the actual environment which might be very
expensive or risky for them. Example used for training pilots instead of using the
actual planes

b. Tutorial
These are learning materials provided in soft copy for the learners to read for
knowledge. Example: e – books

Description @ 1 Mark
Example @ ½ Mark
Total = (2 X 1 Mark) + (2 X ½ Mark)
= 3 Marks

15. a. Dan a computer student noticed that every time a person enters the computer lab the
computer screen flickers. Identify three reasons why the monitor might be flickering
i. There may be a loose connection to his computer hence flckering when
touched
ii. Cables may be laid on the path way hence flickering when stepped on
iii. Electronic Interference - External factors can also cause monitor flicker, it is
possible that additional electronic devices, emitting their own waves, could be
interacting with the monitor screen, causing a flicker. Generally, any strong
magnetic force or device that sends out signals such as mobile phones could
cause it.

Or any other correct responce

Reason @ 1 Mark
Total = 3 X 1 Mark
= 3 Marks

b. State two ways in which the problem can be solved

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 i. Proper insulation of cables
ii. Laying the cables in trunks away from busy pathways
Or any other correct responce
Solution @ 1 Mark
Total = 2 X 1 Mark
= 2 Marks
SECTION B (60 MARKS)
Answer question 16 (Compulsory) and any other THREE questions from this section.
16. To maintain a strategic fit safaricom is introducing a tariff called the mega tariff that will
lower costs to safaricom to safaricom calls and calls to other networks. Calls to safaricom
networks will be charged according to the time of the day as listed below:
-Between 8am to 12 noon-6 Kshs
-Between 12 noon to 2 pm-0.8 Kshs
-Between 2 pm to 6 pm-2 Kshs
-Between 6 to 1 am-4 Kshs
-Between 1 am to 8 am-1 Kshs

Internal calls to other networks are charged at a fixed rate of 7 Kshs between 8am to 8 pm
and to while international calls are charged at a rate of 25 Kshs between 8 am to 8 pm
and Kshs 35 for the rest of the day. All calls are charged per minute usage.

Mr. Wasswa Bbaale a business man who makes both internal and external calls would
like to make maximum use of this tariff.
(a) Write a pseudo code that would show him know the charges of calls with an
appropriate label when he inputs type of call and the time where appropriate. Use
a 24 hour clock.

START

READ calltype
CASE calltype OF
“Safaricom”:
READ time
CASE time OF

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 8 to12: charge=6
12 to14: charge=0.8
14 to 18: charge=2
18 to 1: charge=4
1 to 8: charge=1

ENDCASE

“Other Networks”:
Charge=7
“International”:
READ time
CASE time OF
8 to 20: charge=25
ELSE
Charge=35
ENDCASE
ENDCASE
PRINT “call on mega ongea now at,”charge,”shillings per minute on safaricom to”,
calltype,”calls”

STOP

Note: Award marks as follows

Input- ½ calltype, ½ time=1 mark
Output- ½ for output, ½ for appropriate label=1 mark
Logic – selection construct= 1/2
Decision (proper branching)-1 mark for 3 correct selections – ½ for two selections =1 mark
Process

-International calls-1
-Calls to other networks – ½
-Safaricom calls- 2½
Use of 24 hour clock- ½ Mark

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(b) Design a flowchart for the pseudocope in 16 (a) above (7 marks)

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 Note: award marks as follows
Correct symbols – ½
Start /stop symbols - ½
Input – ½
Output – ½
Correct logic – ½
Correct use of symbols – ½
Decisions
-Based on calltype – ½
-Based on safaricom to safaricom calls-2
-Based on international calls- 1
-Based on calls to other networks- ½

17. (a) Explain how an operating system controls I/O devices. (2 marks)
The operating system manages the use of input and output devices. This is done
by the use buffers .The operating instructs input and output buffers to take
inputs from an input device or to take outputs from the processor while the
process using the input or output is suspended .when the process which needs
the input is made active once again, the operating system will command the
buffer to send data.

(b) Maintaining security is one of the functions of the operating system. Explain how
the operating system maintains security.
Maintaining security-in networks and larger computers each user is given a
username or ID and passwords to gain access to the computer system. the
operating system keeps a register of all the names so that the only persons with
valid usernames or IDs passwords can access the system. The operating system
keeps a log which records users logged in, the length of time each user stayed
in the system and what they did.

(c) Distinguish between the following pairs of terms

(i) Indexed sequential and direct file organizations
In direct access the computer can go directly to the record you want without
reading the preceding records. For example, to access a record, the
computer goes directly to it without having to go through what is in in front of
it. In indexed sequential file organization the records are stored in a particular
order using a key file. However the file in which the records are stored contains
an index that lists each record by its key field and identifies its physical location
on the disk. The records in an indexed sequential file can either be accessed
directly or sequentially (one after the other).
(ii) State any TWO factors to consider when selecting a data processing mode
- Link between applications
- Area of application
- Volume of data to be processed
- Urgency of output
(d) (i) Using appropriate examples, differentiate between distributed and centralized
processing modes. (3 marks)
Distributed processing modes is a mode of processing where two or more
geographically dispersed networked computers belonging to the same
organization share all or some processing tasks whereas centralized processing

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 is a mode of processing where a host computer (central computer) does all the
processing tasks of the terminals (users) connected to it.

(ii) State one advantage and one disadvantage of the processing modes in 17 (d) (i)
above (2 marks)

Centralized processing
Advantages
-The processor idle time is eliminated
-User interaction is possible through the terminals
-Queries are possible since files are held online

Disadvantages
-Not reliable with regard to data security
-Response time is slow where there are many tasks
-Users have no control over the central processor
-When the processor is down all the operations are paralyzed

(e) (i) With reference to an operating system ,differentiate between formatting and
partitioning (2 marks)
Formatting is preparing a disk so that the operating system can write
information on it by defining the tracks and sectors. Partitioning a disk refers
to the process of dividing a large physical disk into two or more logical drives
(partitions).

(ii) List any TWO types of user interface. (1 mark)

-Command line
-Menu driven
-Graphical user interface

18. (a) Using eight bits and two complement, subtract 7810 from 1710 . Give
your answer in decimal notations. (3 marks)
Convert the numbers to binary and make the bits equal-1 mark
7810 - 10011102
1710 - 00100012

Complement the negative number and add 1 to the ones complement

Complement of 01001110 = 10110001 - ½ mark

Add 1 + 1
101100102 - ½ mark

Add the two numbers 000100012

+ 101100102
110000112 - ½ mark

Conversion to decimals (- 128 + 64 + 2 + 1) = - 6110 ½ mark

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 (c) Convert 11011011111.11112 to:
(i) Octal (2 marks)

Group the bits in to threes

011 011 011 111 .111 100 - 1 mark
3 3 3 7. 7 4 - ½ mark

= 3337.748 - ½ mark

(ii) Hexadecimal (2 marks)

Group the bits in to fours

0110 1101 1111. 1111 - 1 mark
6 D F F - ½ mark

= 6 DF 16 - ½ mark

(iii) Decimal (2 marks)

110110111111.1111

210 + 29 + 27 + 26 + 24 + 23 + 22 + 21 + 20 + 0.5 + 0.25 + 0.125 +

0.0625 - 1 mark

1024 + 512 + 128 + 64 +16 + 8 + 4 + 2 + 1 + 0.9375

= 1759.9375 10 - 1 mark

(d) State any two methods used to gain access to a computer system. (2 marks)
- by using weak access points
- through hacking

(e) (i) Distinguish between peer to peer client server LANS (2 marks)
Client server LAN is a LAN that consists of requesting computers called clients
and a computer that provides services to the clients called the server.
Peer to peer LAN is a LAN where all the computers on the network
communicate with one another directly without relying on the server.

(ii) Atieno was very happy when she bought a safaricom 2G modem for she was
able to easily connect her computer to the internet. After six months she noticed
it was taking her too long to connect to the internet .State two possible causes of
the problem. (2 marks)
- Many people may be using the same band
- The bandwidth she is using is narrow.

19. (a) (i) Explain any TWO causes of system change. (2 marks)
-Errors in the system

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 -Change in user requirements
-Expansion /growth of the organization
-Technological changes
-Frequent failure of the system

(ii) Explain any THREE causes of system maintenance (2 marks)

-High failure rate of the existing system
-Slowness of the system
-Complaints from users
-Lack of security
-High cost of maintenance

(b) (i) Use of questionnaire is one of the most popular fact finding methods .State
any TWO advantages and TWO disadvantages of using this method to gather
data. (2 marks)
Advantages
-Most questionnaires can be answered quickly
-Responses can be tabulated and analyzed quickly
-It is an inexpensive method of fact finding

Disadvantages
-The number of respondents is usually low
-There is no guarantee that an individual will answer all the questions
-Questionnaires are inflexible.

(ii) Explain the importance of requirement specification phase of system development

It enables the systems analyst determine the equipments needed for the new
system.

(c) Explain TWO reasons why a new system is tested before implementation.
-To detect and remove bugs (errors)
-To ensure the program works properly
-To ensure the program solves the intended problem

(d) (i) State TWO duties performed by a systems administrator

-Installing and configuring servers
-Installing and configuring application software
-Creating and maintaining user accounts.
-Backing up and restoring files
-Monitoring and improving system performance
-Configuring a secure system and maintaining system security.
(ii) The principal of a school is attempting to convince his staff to use CAL and CAI
software .State one benefit and one limitation of using such software.
(2 Marks)
Benefits
- They use multi media that make learning more interesting and
interactive
- Students can learn on their own and at their own pace even in the
absence of a teacher.

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 - Abstract concepts can often be explained more clearly with the use of a
multimedia
Limitations
- It reduces face to face interaction with others
- Lessons are set in a predefined order and students can only -- follow in
that order thus hindering creativity.

(e) State ONE advantage and ONE disadvantage of using expert systems in medicine
(2 marks)
Advantages
- Experts can use the system to arrive at a faster, more accurate
conclusion
- It can support a doctor who is doubtful of his decision because of lack of
experience.
Disadvantage
- The system cannot learn from its mistakes
- Lack instinct and common sense which are essential for decision
making

20. (a) Explain THREE types of communication links that may be used to get
an internet connection.
- Dedicated links-this provides permanent connection to the Internet
- Remote network access-this provides access to the internet via satellite
dish
- SLIP/PPP (serial line internet protocol /point-to-point protocol)-to get
access to the internet, one must dial up an internet service provider
which gives you access to the internet.

(b) (i) Differentiate between the internet and World Wide Web (2 marks)
The internet is a network of networks that connect computers across the world
while the World Wide Web is a part of the internet that which stores
information in multimedia form.

(ii) Technology has been blamed for polluting the environment .Explain how the
computer technology has contributed to this. (2 marks)
- The use of solvents in the manufacturing of computers can harm the
environment.
- Disposal of old and used computer parts are harmful to the environment
because they do not decompose.

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(c) A company that makes and sells vehicles receives orders from various clients .the
Company wants to enter their orders in to a database. Study the table structure
below and answer the questions that follow.
Field name data type field size
Order number number long integer
Order date date/time
Supply date date/time
Product code text 5
Consumer ID number long integer
Customer FName text 15
Customer Lname text 20
Customer phone number long integer
Delivery address text 30
Product type text 15
Product name text 10
Quantity ordered number long integer
Product prize number long integer

(i) Split the above table structure in to THREE tables and for each table identify an
appropriate primary key. (5 marks)
Order table
Order number number long integer
Order date date/time
Ordered quantity number long integer
Supply date date/time

Primary key: order number

Customer table
Customer ID number long integer
Customer FName text 5
Customer LName text 20
Customer phone number long integer
Delivery address text 30

Primary key: customer ID

Product table
Product code text 5
Product type text 15
Product name text 10
Product prize number long integer

Primary key: product code.

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