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Q&A-KCSE Computer Studies Paper 1

Name two other input/output devices used at the POS terminal apart from keyboard and barcode reader and give a use for each device.

device: beeper/loud speaker
use: to indicate barcode correctly read/error in reading barcode
device: (LCD) screen/monitor
use: to show prices and other information about goods
device: touch screen
use: to show prices and other information about goods/to select items that need to be
weighed/identified
device: weighing machine
use: to find weight of loose items (e.g. fruit) to enable pricing
device: (magnetic) card reader/CHIP and PIN reader
use: to read customer’s debit/credit card/enable customer to pay for goods using a
credit or debit card
device: printer
use: to print receipts

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Differentiate between bus topology and star topology of networks. What are the advantages and disadvantages of star topology over bus topology

  • Bus topology is characterised by common transmission media shared by all the connected nodes
  • Star topology is characterised by a central switching node connected directly to each of the multiple nodes in the network

Advantages of Star topology over Bus topology

  • Faster communication as compared to bus topology
  • Independent line of connection allows freedom of removing or adding nodes

Disadvantages of Star topology over Bus topology

  • Expensive as compared to the bus topology
  • Long cable length
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Suggest one disadvantage to the programmer of using a high-level language instead of a low-level language.

  • not able to directly manipulate the hardware
  • may need to wait for translation before running
  • the program may be less efficient.

 

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State Examples of utility programs

 

Encryption software

  • Scramble/encode/mix up data so it cannot be read/understood if intercepted/stolen

Defragmentation s/w

  • Move free space together and Move files together hence enabling Faster access to files

(Data) compression s/w

  • Reduce the file size of files or makes files smaller inorder  To use less storage space
  • enables Faster transmission
  • enables storage of more files

Anti-virus / anti-malware s/w

  • To help protect computer/data against viruses/malware
  • To scan the computer to look for/quarantine/remove viruses/malware

Disk analysis and repair s/w

  • Scan disk and look for faults
  • Prevent the loss of data due to faulty disk

Auto-update

  •  Checks Internet for new versions of software/OS
  • Downloads and installs without user interaction

Firewall

  • Examine incoming and outgoing traffic
  • To help restrict/prevent unauthorised access over a network

...over a network/external source

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Computer Studies Paper 1 2021  KCSE Prediction Section B Qs. 17,18 and 19

17. a) i) Explain the term search as used in the Internet.                                            [2]

A web based application that locates items or information from the World Wide Web

ii) Peter intends to download a movie from the Internet. State the three factors that may determine the total time taken to complete the download.                                           [3]

  • Size of the video/format
  • The bandwidth of the media/speed of network/network traffic
  • Type of browser software
  • Background activities running in the computer
  • Restrictions enforced in the computer/firewall/antivirus
  • Speed of the computer/CPU speed
  • Size of RAM

b) Wakulima online is an organization that runs a web based system for assisting farmers to obtain market for their produce. State four technological reasons that may cause a farmer not to access the organization’s system.                                                                                  [4]

  • Poor network/lack of connection
  • Software failure in the system
  • Hardware failure
  • Lack of access rights
  • System overload/hanging
  • Lack of skills/disability/illiteracy
  • Lack of power supply

c) Explain a situation when each of the following Desktop Publishing program features may be used when creating a publication:

i. Cropping                                                                                                               [2]

Applies to graphics – used to trim/remove/hide some portions in the graphics

ii. Transparency                                                                                                         [2]

Used to make background of a graphic to be clear/visible

d. List two areas where infrared waves are used in data communication.                             [2]

18. a) List four activities of the planning stage of systems development.                             Ignore this question, marks redistributed elsewhere

b) Explain a circumstance when each of the following feasibility studies are carried out during systems development.

i. Technical                                                                                                               [3]

Done to determine whether technology exists to support the proposed solution

 

ii. Economic                                                                                                              [3]

Done to determine whether the proposed solution is economically viable

 

iii. Schedule                                                                                                               [3]

Done to determine whether the proposed system can be done within an acceptable time.

c) Table 1 and Table 2 are related tables in a database. Use them to answer the questions that follow.

Table 1

Dept Code

Dept Name

001

Computer

002

Aviation

003

Engineering

 

Table 2

DeptID

Student Registration No.

Student’s Name

002

St01

Alex Too

003

St02

Naomi Komi

002

St03

Peter Kengo

 

i. Identify the appropriate primary key for each table.                    [2]

Table 1 – Dept code, Student Registration No

ii. Explain two benefits of enforcing referential integrity in the database. [4]

  • No record can be added in Table 2 if its corresponding record in Table 1 does not exist
  • No record in Table 1 can be deleted without first deleting the corresponding record in Table 2
  • Reduces data redundancies/ensures integrity
  • Prevents deletion of related table

19. a) Describe each of the following validation checks as used in data processing.

i. Preserve check                                                                                                      [2]

Ignore this question, marks redistributed elsewhere

ii. Data type check                                                                                                    [2]

Ensure correct type of data is entered for the field

iii. Check digit                                                                                                           [2]

This is a number added/calculated by the computer to a binary number. The check digit ensures correct transmission of the binary number.

b. Write each of the following abbreviations in full:

i) BCD                                                                                                                                    [1½]

Binary Coded Decimal

ii) EBCD                                                                                                                                 [

This question was thrown out and marks redistributed elsewhere

iii) ASCII                                                                                                                    [1½]

American Standard Code for Information Interchange

c) Using 10-bits binary number system, perform the following decimal operation using two’s complement.                                                                                                                                   [6]

12910 - 12810

+129 = 00 1000 0001

128 = 00 1000 0000

-128 = 11 0111 1111 (ones complement)

                            +1

          11 1000 0000 (Twos complement)

129- 128

     00 1000 0001

+ 11 1000 0000

 100 0000 0001

Hence = 00 0000 00012 or 12 (the overflow bit is ignored)

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Differentiate between active matrix and passive matrix LCDs

 

  • Passive matrix create images by scanning the entire screen whereas active matrix displays are made using thin-film transistors technology(TFT)
  • active matrix  display has a higher resolution compared to passive matrix
  • Active matrix consume more energy than passive matrix
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Describe how the database can be recovered from a system failure

  • mirrored hard disk/hot standby/second computer
  • re-run the old master file with the transaction file
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Describe two effects on society of an increase in the use of the Internet for e-commerce.

  • loss of jobs as some traditional shops/banks close
  • lower profits for companies that do not get involved with e-commerce
  • decline of leisure shopping as goods are bought on-line
  • city centres becoming deserted as shops/banks close down
  • gap between rich and poor widening as richer get savings from
  • shopping on-line
  • more people choosing to interact with computers rather than people
  • increase in small businesses
  • less pollution/travelling
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A computer game involves driving a racing car around a track. State which two modes of data processing  would be appropriate, justifying your answers

  • Real time  E.g. turning the wheel must turn the car immediately
  • On line - Otherwise system cannot be real time
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State advantages of solid state storage media

  • Portable
  • Light
  • Faster access speed
  • No moving parts
  • Efficient power consumption
  • Durable
  • Small physical size
  • Large storage capacity
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What is repetitive strain injury?

  • the pain felt in muscles, nerves and tendons caused by repetitive movement and overuse.
  • Injury as a result of repetitive use of parts of the body while performing work
  • Strains and injuries due to prolonged typing and use of the mouse
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One characteristic of a robot is its mechanical structure.
State two other characteristics of a robot

  • It has electrical components.
  • It is programmable.

 

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Identify the network component that uses the IP address to send data only to its correct destination

Router

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State two computer-based careers  that have arisen as a result of  computer-based data processing in a factory    (2 marks)

System analyst

Web designers

Network administrators

Database administrators

Programmers

Computer technicians

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Describe what is meant by a clock speed of 3.8 GHz.

  • The number of FDE cycles run per given time/second
  • the frequency that the clock ‘ticks’
  • 3.8 billion cycles/instructions per second
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Students are using their wireless notebooks to complete their work in a classroom. They will need to connect wirelessly to a printer to print their answers at the end of the lesson.
Describe how CSMA/CA (Carrier-sense multiple access with collision avoidance) operates in the above scenario.

  • All nodes ‘listen’ for traffic to sense when the network is idle.
  • When a node wishes to transmit, it transmits a ‘request to send’ frame’ (RTS)
  • The intended receiving device will transmit a ‘clear to send’ (CTS) frame if it is available.
  • All other nodes ‘sense’ the network is busy and wait a random amount of time before trying to transmit
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Describe the role of the one-dimensional array in programming

  • holds an indexed sequence of variables of the same data type
  • Arrays can be used to store values of the same data type and the array is then used as a singular variable to increase efficiency
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Describe the input, processing and output from a computerised traffic-control system.

input

  • from sensors
  • from camera images [Max 2]

processing

  • analyse data from sensors
  • calculate average traffic flow/speed
  • send signals to adjust change lights/timing

output

  • change lights at the junction
  • change timing plan
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Distinguish between an optical scanner and a magnetic ink scanner

  • Optical scanner is used read data by use a beam of light while a magnetic ink scanner is used to read data encoded/written using magnetic ink by magnetising the ink characters and translating them
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Utility software are operating system programs designed to maintain the functionality of a computer system.

Describe three types of utility software that are provided to help maintain the security and integrity of computer data.

  1. Virus scanning / Anti-virus. Used to locate and delete viruses / scans and compares files with databases of known viruses.
  2. Firewall: checks data packets / examines source address / filters out unexpected packets.
  3. Back up. Copies data onto a separate storage device for use if the original data is lost or corrupted.
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