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Q&A-KCSE Computer Studies Paper 1

Explain the functions of the following parts of the CPU

Control Unit; Decodes instruction; Controls the fetching and writing of data;

Arithmetic Logic Unit/ ALU; Executes mathematical instructions;  Executes logical instructions; Compares values held in registers;

 Clock; Controls the number of instructions carried out each second;   allows the CPU to synchronize operations;

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(ii) The organisation has chosen wireless connectivity over wired connectivity for its new office building. There is no significant difference in the cost of installing either.
Give three reasons why the organisation might prefer wireless connectivity.

May not have space for cables to be installed

Employees and visitors can move around the building without disconnecting

Adding new users just means giving out the SSID and password

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Outline a factor that can influence the performance of a network.

  • The different factors that can influence the performance of a network include: bandwidth, network design, data collisions, and excess broadcast traffic.
  • The bandwidth can influence through the method of transmission and medium used
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Describe the principles of operation of  laser printers and describe how they are applied in real-life scenarios

  • A laser printer makes use of powdered ink and static electricity to print
  • Unlike inkjet printers which print line-by-line, laser printers print the whole page in one go

Steps

  • The data from the  file to be printed is sent to a printer driver
  • The printer driver checks that the data is in an understandable format
  • The printer driver checks if the printer is able to carry out the print job
  • The data is sent to the printer and is stored in a printer buffer
  • A printing drum in the printer is given a positve charge. A laser beam removes the positive charge in some areas. This leaves negatively charged areas which matches the characters/images to be printed
  •  
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Explain the difference between
(i) serial and parallel,
(ii) simplex and duplex
modes of data transmission.

  • Serial is the transmission of data one bit at a time/through one wire
  • Parallel is the transmission of data more than one bit at a time/many wires
  • Simplex is the transmission of data in one direction only
  • Duplex is the transmission of data in both directions simultaneously
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Website data is broken down into packets to be transmitted to a user. Describe the structure of a data packet.

It has a header

  • that contains the destination address
  • that contains the packet number
  • that contains the originator’s address

It has a payload

It has a trailer.

 

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Achieng plays an online game on her laptop. List two ways she can reduce the risk of developing repetitive strain injury(RSI)

  • By use of an ergonomic keyboard
  • She should take regular breaks from her computer and stretch her joints
  • She should use standard furniture with an upright backrest to reduce strain on the back
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Identify two advantages to a programmer of using a high-level language instead of a low-level language.

  • it is easier / quicker to read/write/understand
  • it is easier / quicker to debug
  • code is portable.

 

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State two reasons why the data in fields such SEX field in a database should be coded.

  • less errors on input
  • requires less storage space
  • validation
  • quicker to input
  • quicker to find
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Viruses, pharming and phishing are all examples of potential Internet security issues.
Explain what is meant by each of these three terms.

Virus

  • - program/software that replicates/copies itself
  • – can delete or alter files/data stored on a computer
  •  – can make the computer “crash”/run slow

Pharming -

  • malicious code/software installed on a user’s hard drive/actual webserver
  •  – this code redirects user to a fake website (without their knowledge)
  •  – to obtain personal/financial information/data

Phishing

  • - legitimate-looking emails sent to a user
  • – as soon as the recipient opens/clicks on the link in the email/attachment …
  • – … the user is directed to a fake website (without their knowledge)
  • – To obtain personal/financial information/data
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What is meant by RAID technology?

RAID (Redundant Array of Independent Disks) technology refers to a method of combining multiple physical disk drives into a logical unit to improve performance, data availability, and data redundancy. RAID technology is commonly used in storage systems to provide fault tolerance, data protection, and increased storage performance.

The primary purpose of RAID is to create a more reliable and robust storage solution by spreading data across multiple drives and implementing various data redundancy techniques. This helps to mitigate the risk of data loss and system downtime in case of drive failures.

There are different levels or configurations of RAID, each offering different features and trade-offs. The most commonly used RAID levels are:

  1. RAID 0 (Striping): Data is split evenly across multiple drives, resulting in increased performance as data can be accessed from multiple drives simultaneously. However, there is no redundancy, so if one drive fails, data loss can occur.

  2. RAID 1 (Mirroring): Data is duplicated or mirrored across two drives, providing redundancy. If one drive fails, the other drive can still function and serve the data. RAID 1 offers data protection but does not offer increased performance.

  3. RAID 5 (Striping with Parity): Data and parity information are striped across multiple drives, providing both increased performance and fault tolerance. Parity information allows for the recovery of data in case of a single drive failure. RAID 5 requires a minimum of three drives.

  4. RAID 10 (Combination of Mirroring and Striping): RAID 10 combines elements of RAID 1 and RAID 0. It involves mirroring data across two sets of drives and then striping the mirrored sets for increased performance and fault tolerance. RAID 10 provides high levels of data redundancy and performance but requires a minimum of four drives.

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State and briefly describe three program control structures

Sequence: Sequential execution of a program one line after another

Selection:  Involve the a decision between two or more options e.g  if...then...else

Loops/Repetitions: Used for looping i.e a line of code can be made to execute a given number times before terminating.

Aeroplanes now use Global Positioning Systems (GPS) to determine their location.

Describe how the computer on board the aeroplane uses GPS to find its exact location

Give two benefits of using GPS in this application

Describe how the computer on board the aeroplane uses GPS to find its exact location

satellites transmit signals to onboard computers
computers receive/interpret these signals
system depends on very accurate timing/use of atomic clocks
each satellite transmits data indicating location and time
computer in aeroplane calculates location based on at least three satellites
at least 24 satellites in operation at any one time
position accurate to within one metre
can also calculate altitude of aeroplane
ref to “triangulation”:

Give two benefits of using GPS in this application

safer as the known location is exact/more accurate
reduces the possibility of pilot error
allows accurate estimation of arrival time
display and guide the pilot to the nearest airport in case of emergency

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Give three characteristics of an IP address.

  • consists of values between 0–255 / 0–FFF
  • values are separated by full stops/colons
  • it is a unique address
  • can be static or dynamic
  • can be public or private
  • can be IPv4 / have four groups of digits
  • can be IPv6 / have eight groups of digits
  • in IPv6: can replace groups of zeros.
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State three categories Operating Systems grouped according to user interface

  • Commandline/ Character interface Operating systems
  •  Menu Driven Operating Systems
  •  Graphical User Interface Operating Systems
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Describe the purpose of the control unit (CU) within this computer.

  • It sends control signals that manage the transfer of data and instructions within the CPU
  • It decodes an instruction using an instruction set
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Distinguish between a file and a folder

A file is a collection of related data given a unique name while a folder is named storage location on a storage media that contains related files

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Name three types of cables used in data communication

Twisted pair cables

Coaxial cables

Fibre optic cables

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Give two examples of each of the following application packages       

a)Spreadsheets                                                                                                                               (2mks)

  • Microsoft Excel
  • Lotus 1-2-3
  • Google Sheets
  • OpenOffice Calc

                                           Any 2 @ 1mk

 

b) Word processors                                                                                                                          (2mks)

  • Microsoft Word
  • Wordpad
  • Corel WordPerfect
  • Lotus Word Pro

 

                                         Any 2 @ 1mk

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Differentiate between uploading and downloading a file

Uploading a file  refers to the process of transferring a file from a local computer to a remote webserver while downloading a file refers to the process of transferring or copying a file from a remote webserver to a local machine

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