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Q&A-KCSE Computer Studies Paper 1

Explain why it is not always true that a computer which has  a quad-core processor runs twice as fast as a computer with a dual-core processor

 

  • Software may be designed to run on 1 core and not multiple cores
  • depends on the task(s)  i.e some tasks cannot be split across cores
  • Clock speed also affects speed i.e dual core may have a faster clock speed and quad-core may have slower clock speed so one task may be run faster/slower
  • RAM size also affects speed i.e Quad-core may have less RAM  amount of VM being used
  • Cache size also affects speed i.e Quad-core may have less cache
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State two ways in which data validation is implemented on an input form of a database application

  • By setting the validation rule for the input controls on the property sheet in design view
  • By use of VBA to restrict user inputs for a given control on a form
  • By use of queries to restrict options available for the user in a combo box or listbox
  • Setting correct data types for the fields in table the design
  • Enforcing referential integrity in database relationships
  • Use of input mask for the controls on the property sheeet in design view
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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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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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The data before encryption is known as .................................................. text.
To scramble the data, an encryption .................................................., which is a type
of .................................................., is used.
The data after encryption is known as .................................................. text.
Encryption prevents the data from being .................................................. by a hacker

The data before encryption is known as .......plain.................. text.
To scramble the data, an encryption ......................key.........................., which is a type
of ...................key............................, is used.
The data after encryption is known as ....................cipher............................. text.
Encryption prevents the data from being ......................understood...................... by a hacker

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 Lucy wrote: “I should validate the input into my database by typing in the same data twice”.Why was her statement incorrect?

  • she had actually described verification
  • data could be incorrect, therefore same incorrect data typed in twice
  • accept description of validation process e.g. range check
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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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State two advantages and one disadvantage of having a network of computers, rather than a series of stand-alone machines, in a school classroom.

Advantages

  • Sharing of software and data files
  • Sharing of hardware, e.g. printers
  • Communication

Disadvantages

  • Security of files is more of a problem
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Explain why solid state storage is the best choice for a fitness tracker.

  • Because it will be subject to movement  and it does not use mechanical/moving parts

          OR

  • Solid state storage is smaller/more compact so better suited for a wearable device

          OR

  • Doesn’t have moving parts  because they could be disrupted during use
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State three advantages of  biometric authentication

  • Protection against Password-related Vulnerabilities: Traditional password-based authentication methods are vulnerable to various risks, such as weak passwords, password sharing, or password theft.
  • Stronger Access Control: Biometric readers add an additional layer of access control to laptops. Even if someone gains physical possession of the laptop, they would still need the authorized user's biometric data to unlock it and access the data. This helps prevent unauthorized individuals from accessing sensitive information stored on the laptop,
  • Audit Trail and Accountability: Biometric authentication systems often come with built-in logging and auditing capabilities. This means that each time someone accesses the laptop using their biometric data, it can be recorded and associated with a specific user. This creates an audit trail, allowing organizations to track and monitor access to laptops and establish accountability in case of any security incidents or breaches.
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List three characteristics of Internet Protocol version 6 (IP6).

  • has a significantly larger address pool than previous version
  • features a client-side address assignment
  • has built-in encryption
  • enables one device to have many network addresses
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What are computer networks?
A set of connected computers and other devices which share resources such as software, internet connection,printers etc
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Describe three other different categories of malware.

Trojan (horse); a program which misleads the user into thinking it is another

piece of software which, when run, executes another program;

Spyware; a program which records data such as usernames and passwords on

a host system and forwards the information to a third party;

Adware; code embedded or attached to program files which will persistently

show adverts (that attempt to generate revenue);

Worm; code which will run autonomously and replicates itself on a host system;

Ransomware; a program that encrypts user’s data to make it unreadable until

they pay for the key;

Remote Access Tool (RAT); allows access to control and monitor a computer

from a remote network location;

Rootkit; malware that has managed to gain ‘root’ admin privileges;

Bots/Zombies; a program installed on a computer that performs a job for the

remote owner of the bot/zombie such as sending spam or sending web requests

to perform a DOS or attacking a computer system;

Scareware; malware that tells you something is wrong with your system in an

attempt to get you to make a purchase;

Keylogger; a program that monitors/records a user’s keystrokes in order to steal

passwords/confidential details;

KCSE 2021  Prediction Computer Studies Paper 1  Q.16 (c)

c) Distinguish between a source program and a compiler as used in computer programming. [2]

Source program is the original program in a high level language as written by the programmer while a compiler is a program translator that converts source program to object code.

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State advantages of hardcopy output

  • They are accepted as exhibits in cases of litigation
  • Can be used without a computer
  • they are difficult to change without leaving any trace
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Describe the query criteria given below

 

(a) Like "*kenya*"

  • Returns the records of all countries that contain the string "kenya"

(b) Like "*ina"

  • Returns records for all countries/regions whose names end in "ina", such as China and Argentina.

(c) Like U*

  • Returns records for all countries/regions whose names start with "U", such as UK, USA, and so on.

(d) Not Like U*

  • Returns records for all countries/regions whose names start with a character other than "U".

(e) >= "Mexico"

  • Returns records of all countries/regions, beginning with Mexico and continuing through the end of the alphabet.

(f) Like "[A-D]*"

  • Returns records for countries/regions whose names start with the letters "A" through "D".

(g) "USA" Or "UK"

  • Returns records for USA and UK.

https://support.microsoft.com/en-us/office/examples-of-query-criteria-3197228c-8684-4552-ac03-aba746fb29d8

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Describe two health risks associated with the increased use of computers.

  • RSI in wrists or fingers from prolonged typing or repeated clicking of mouse button
  • headaches/eyestrain/dry eye from staring at a monitor for long periods of time/glare from monitor
  • back ache/strain from sitting in the  same position for a long time/using chair with no adjustment
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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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Explain, using examples where appropriate, the meaning of these computer terms

(a) byte ..................................................................................................................................
..........................................................................................................................................
......................................................................................................................................[2mks]
(b) compiler ............................................................................................................................
..........................................................................................................................................
......................................................................................................................................[2mks]
(c) handshaking .....................................................................................................................
..........................................................................................................................................
......................................................................................................................................[2mks]
(d) technical documentation ..................................................................................................
..........................................................................................................................................
......................................................................................................................................[2mks]
(e) simulation .........................................................................................................................
..........................................................................................................................................
......................................................................................................................................[2

(a) byte

  • fixed number of bits, 8 bits
  • represents a character


(b) compiler  program

  • converts/changes/translates high-level language into machine code/machine language/low-level language/object code
  • changes each high-level language instruction into machine code instructions
  • produces an independent program capable of being executed by itself
  • all (syntax errors) listed
  • converts the whole program before execution/in one go
  • converts source code to object code

(c) handshaking

  • exchanging of signals to establish communication between two devices/computers e.g. printer and computer, modem and computer

(d) technical documentation

  • documentation to ensure that the system can be maintained/updated/altered/developed/upgraded
  • trouble shooting/correcting errors/correcting faults
  • explanation of what the program does/how the system works
  • contains file structures
  • algorithms/flow charts/pseudo code
  • program listings
  • hierarchical chart

(e) simulation

  • studying the behavior of a system by using a model/represents real-life/mathematical representation
    e.g. flight simulator (or others), hazardous applications results can be predicted
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Describe and give an example of one syntax and one logical programming error.

Syntax
An error that occurs when a command does not follow the expected syntax of the language, e.g. when a keyword is incorrectly spelt
Incorrect: IF A ADN B Then
Correct: IF A AND B Then

Logical
An error that causes a program to output an incorrect answer (that does not necessarily crash the program)
An algorithm that calculates a person’s age from their date of birth, but ends up giving negative numbers

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