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Q&A-KCSE Computer Studies Paper 1

A company has a website that is stored on a web server.
(a) The 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, the packet number, and the originator’s address
  • it has a payload
  • it has a trailer.

 

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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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Explain the differences between parallel running and direct changeover as ways of implementing the new system.

Direct changeover – new system replaces existing system immediately/overnight

 Parallel running – new system runs alongside/together with existing system

Parallel running – there is always the old system to fall back on in the event of the new system failing/information is not lost/always a second copy

Direct changeover – if things go wrong lose all data/old system is not available

Direct changeover – training is more difficult to organise

Parallel running – training can be gradual Parallel running is more expensive to implement than direct changeover....

Direct changeover is a quicker method of implementation than parallel running

Direct Changeover: The old system is stopped completely, and the new system is started. All of the data that used to be input into the old system, now goes into the new one.

 Parallel Running: The new system is started, but the old system is kept running in parallel (side-by-side) for a while. All of the data that is input into the old system, is also input into the new one. Eventually, the old system will be stopped, but only when the new system has been proven to work.

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Explain the following terms

(a) Disk mirroring

(b) Encryption

(c) Backup

(a) Disk mirroring- Data is written on two or more disks simultaneously.

(b) Encryption - Contents are scrambled so they cannot be understood without a decryption key

(c) Backup - A copy of the data is taken and stored in another location

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Give an example of where a PAN could be used

  • connecting wireless headphone to a phone
  • Using a wireless mouse, keyboard etc
  •  
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Sarah uses a range of computing devices to complete her studies, including a desktop computer at home, a laptop at school and her mobile phone. Outline two advantages of cloud computing for Sarah.

Cloud computing refers to the delivery of on-demand computing resources over the internet. Instead of relying on a local server or personal computer, cloud computing allows users to access and utilize a wide range of computing services and resources hosted on remote servers.

  • Sarah could keep all of her files in the cloud and easily access these with her devices. This way she does not have to keep different version on her desktop and laptop.
  • Flexibility she could access the files from other devices such as the library etc.
  • Disaster recovery if she accidently dropped or damaged a device – all files would be easy to access.
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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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Explain, with examples where appropriate, the following five computer terms.

(a) Buffer

(b)batch processing

(c) e-commerce

(d) simulation

(a) Buffer

  • temporary storage or memory which compensates for the difference speed of peripherals and the CPU

(b)batch processing

  • processing doesn’t start until all data is collected
  • JCL (any reference to Job Control Language)
  • no need for user interaction
  • processed all in one go
  • done at “quiet” times
  • e.g. billing, payroll, cheque processing

(c) e-commerce

  • electronic commerce
  • buying and selling products/services using the internet/computer networks

(d) simulation

  • studying the behaviour of a system by using a model/mathematical representation
  • results can be predicted
  • e.g. flight (or other) simulator, modelling hazardous chemical process

(e) Email

  • sending messages from one device to another using computer networks/Internet
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Explain three ways a computer can store negative numbers                                            (3 marks)

Prefixing an extra sign bit- A negative number is representes by prefixing a digit 1 to the number

Ones complement- This is flipping the binary equivalent of the number

Twos complement- this involves getting the ones complement and then adding a 1

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Differentiate between object code and source code

  • Object code refers to a program in machine language while source code to a program in a high level language that must be translated to object code for it to be machine readable
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Give one reason why a phased implementation would be the best approach to follow in this case.

  • This approach causes minimum disruption
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A car park uses a number plate recognition system. Identify the reason why unsigned integers should be used to record the number of cars entering and leaving the car park, rather than signed integers

  • Unsigned integers store more positive values
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802.3 is the standard for ethernet wired networks and 802.11x is the standard for ethernet
wireless networks.
Outline why standards such as these are important in the development of network devices and
software.

  • Standards specify a set of rules for hardware and/or software used in network communications. Because all manufacturers must adhere to the standards when manufacturing network hardware or software, it means that all devices should be able to communicate, regardless of manufacturer.
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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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Describe two possible causes of computer failure. In each case state how it could have been prevented

  1. Hardware failure
  2. Corrupted software files
  3. Hacking into the system
  4. Power failure
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Describe the main characteristics that distinguish high-level programming languages from low-level languages.

  1. Low level languages do not resemble natural languages they are made up entirely of bit patterns
  2. Low level languages produce code that is executed faster as it is already in a format the CPU can execute / does not need to be translated.
  3. High level languages are easier to understand / learn as commands are more like English / identifiers can be meaningful .
  4. High level languages are easier to use leading to fewer errors.

Journalists are issued with laptops when they start working at a magazine publishing company. The company only uses free open-source software (FOSS).

  • 2.1.1 Explain the concept of open source in the context of FOSS. (2)
  • 2.1.2 Give ONE example of a free operating system the company could install on a laptop. (1)
  • 2.1.3 State TWO disadvantages of using free open-source software.

The laptops are equipped with either an HDD or an SSD.

  • 2.2.1 Users of laptops equipped with HDDs are advised to defragment the HDD regularly.
  • Briefly explain what defragmentation is. (2)
  • 2.2.2 Write out the abbreviation SSD in full. (1)
  • 2.2.3 Explain why an SSD accesses the data faster than an HDD.

The journalists can access their data remotely using virtualisation or Software
as a Service (SaaS).
2.3.1 Define the term virtualisation. (1)
2.3.2 Office365 is an example of SaaS.
(a) Except for remote data access, state TWO benefits of using
SaaS. (2)
(b) Describe how the license model of SaaS works. (2)

  • 2.4 The company takes precautionary measures to protect the magazine's data.
  • 2.4.1 An incremental backup strategy has been implemented to safeguard data. Explain how an incremental backup strategy works. (2)
  • 2.4.2 The company considers installing biometric readers on all the laptops. How would a biometric reader help safeguard the data on a laptop?

 

2.1.1 Explain the concept of open source in the context of FOSS. (2)

  • Is a software whose source available and user can modify and redistribute

Give ONE example of a free operating system the company could install on a laptop. (1)

  • Linux
  • FreeBSD
  • ReactOS
  • Android
  • ChromeOS
  • OpenSolaris

2.1.3 State TWO disadvantages of using free open-source software.

  • Lack of support
  • Security risks
  • Compatibility issues
  • Hidden costs
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Give two other uses of hexadecimal in computer science.

  • colour codes // colour in HTML/CSS
  • error messages
  • locations in memory
  • memory dump // debugging 
  • IP(v6) address
  • ASCII // Unicode
  • assembly language
  • URL.

 

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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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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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