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Q&A-KCSE Computer Studies Paper 1

State the seven layers of the OSI model

  1. Application
  2. Presentation
  3. Session
  4. Transport
  5. Network
  6. Data link
  7. Physical

Name three types of cables used in data communication

Twisted pair cables

Coaxial cables

Fibre optic cables

Identify four different types of computer network.

  1. MAN
  2. WAN
  3. PAN
  4. LAN

Describe two differences between a switch and a repeater

  • a repeater is a two-port device that amplifies a signal from one port to another
  • a switch is a multiport device that uses a table of addresses to send a signal through the correct port

Describe the role of a repeater when used in a network.

a repeater will amplify a signal and resend it to overcome reduction in signal strength (attenuation) because over a distance network signals diminish in size/amplitude (are attenuated) due to characteristics of the media.

Satellite services are used to provide broadband internet connectivity to regional and remote areas of Kenya. State one advantage and one disadvantage of using satellites for this purpose.

Advantages

  • can cover large areas
  • requires minimal land-based transmission support
  • requires minimal infrastructure to provide internet access
  • minimal impact on the environment or humans.

Disadvantages

  • transmission speeds are not comparable with other forms of transmission
  • data costs are expensive by comparison to other forms of transmission
  • expensive to deliver.

State the primary function of the Dynamic Host Configuration Protocol (DHCP) protocol.

  • it generates and/or allocates an IP address

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

Explain two ways in which an interpreter and a compiler are different.

  • They execute code differently – a compiler reads a complete program at once, an interpreter reads a program line-by-line
  • they identify errors in different ways – a compiler does not allow a program to run until error-free, an interpreter runs the program until the first error.

Explain each of the strategies listed below.

(a) Phishing

(b) DoS

 

(a) Phishing

  • Phishing is a strategy that encourages a computer user to part with sensitive information such as bank details hence the term ‘phishing’ – i.e. fishing – trying to catch someone out. For example, a perpetrator sends a user an email that appears to be genuine, for example, pretending to be a bank or a lawyer requesting that the user verify bank account details or send money to assist in the completing of a legal case.

(b) DoS

  • DoS is a means of attack on a specific user/system/website which involves overloading a target with too much network traffic resulting in system slowdown, shutdown or a violation of security.

List two primary functions of a domain name server.

  •  map IP addresses to names and criteria
  • To map directory services
  • Maintain directory of domain names
  • To map URL (web address) to IP address

When developing a network security policy, it is important to understand the threats that can be made against a network. ‘IP spoofing’ and ‘back doors’ are two techniques that can compromise the security of a network. Describe each of these techniques.

IP spoofing

A technique used to gain unauthorised access to a computer whereby an intruder sends messages to that computer from a false IP address

Back door:
An undocumented method of gaining access to a program, online service or an entire computer system

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

Describe three possible threats to the computers connected to the network and give one way each threat can be reduced or prevented

Virus / trojan / worm / malware

  • Piece of software/code/a program that replicates itself  or causes damage e.g. editing/deleting files

Prevention

  • Running anti-virus/anti-malware software 
  • don’t download from unknown sources
  • don’t click on unknown links

Spyware / malware / keylogger

  • Piece of software/code/a program that records actions/key presses and sends this data to a third party analysis

Prevention

  •  Running anti-spyware/anti-malware software/firewall

Data interception / passive

  • Data is sent to another device and is intercepted by a third party

Prevention

  • Encryption

Phishing

  • An e-mail has a link that when clicked directs the user to a fake website that collects personal data

Prevention

  • Network policy // firewall

Pharming

  • A piece of code installed that redirects user to fake website that collects personal data

Prevention

  • Anti-malware or firewall

Hacker

  • Person attempting to gain unauthorised access to the network/computers/ data/files 
  • unauthorised access and then deleting/editing data/files

Prevention

  • Firewall
  • strong password 
  • biometrics
  • penetration testing

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.

 

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.

 

A web server has an internet protocol (IP) address. 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.

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

Router

The website has a uniform resource locator (URL).
An example of a URL is given.
https://www.google.co.ke/index.html
Complete the table to identify the name of each section of the URL.

https :  protocol

google.co.ke: domain name

/index.html: webpage/file name

 

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