Computer Studies Paper 1 KCSE 2025  Revision Set 1

Give two reasons for connecting computers in a network.

Can share files/data
Can share applications/software
Can collaborate
Can share peripherals (printers, speakers)
Can share connectivity (Internet connection, hotspot)
Can access files from any computer / hot desk
Central control/management (security, software updates, backup, remote support, users, remote monitoring)
Allows communication (email, social media, video
conferencing, online meeting, collaborative games) 

Describe one way a local area network (LAN) is different from a wide area network (WAN)

A LAN covers a small (geographic) area / a WAN covers a large  (geographic) area (2)
A LAN uses infrastructure owned by one company / a WAN uses third-party infrastructure (2)
A LAN connects individual devices / uses switches (1), whereas a WAN connects LANs / uses gateways (1)

Describe how a firewall protects a local area network (LAN)

Monitors/checks traffic (1) using a set of rules / list of
authorized/unauthorized computers/addresses/protocols (1) to decide if data is allowed into or out of the network (1)

State the name of an email protocol.

POP3
IMAP
SMTP

Explain one disadvantage of using a star network topology.

All communication could fail (1) because/if the central device fails (1)
It can be difficult/expensive to set up (1) because each device needs a cable to connect to the central device (1)
The number of devices that can be connected is limited (1) because the central device supports a fixed number of connections (1)

Some low-level programming languages use mnemonics.
(i) State the purpose of a mnemonic.
To represent an instruction/command
To make an instruction/command easy to
read/write/learn/remember/understand
An instruction in a set of instructions

(ii) State the type of low-level programming language that uses mnemonics.
Assembly language

(iii) Mnemonics are one characteristic of some low-level languages.

Describe one other characteristic of a low-level language.

They are microprocessor/CPU/machine specific (1) so they can manipulate the hardware directly (1)
They can be highly optimised (1) to make efficient use of the hardware/execute more quickly/use minimal memory (1)
Each line of code (1) is one instruction only (1)

State the name of the high-level programming language translator that executes a line of code immediately after translating it.

Interpreter

State the two items held in RAM according to the von Neumann architecture.

Data
Instructions

Describe how data is stored on optical media.

A laser heats/burns (areas of a disk) (1), which creates lands/pits (1) representing binary / 1s and 0s (1) 

State the type of secondary storage that stores data as electric charges.

Solid state / flash
Accept ‘SSD’ for solid state

An embedded computer system is part of a larger machine.
State two characteristics of embedded systems that make them different from general purpose computers.

Limited processing resources
Low power consumption
Simple/robust operating system
Low cost per unit
Smaller in size
Less storage
Limited user interface

Robust software must be free from vulnerabilities before it is released to users.
Programming bugs are one type of vulnerability.
State two other types of vulnerability

Programming language specific vulnerabilities (directly
manipulating memory)
Security (vulnerability)
Weak design

Insufficient testing
Bad programming practices (not following standards, using unvalidated 3 rd party libraries)
Inadequate validation (that fails to prevent
incorrect/inappropriate data input)
Inadequate authentication (that enables hackers to gain unauthorised access)
Sensitive data not encrypted 

Some users are given administrator privileges.
Explain one way an operating system allows an administrator to manage users.

Users can be added/deleted (1) so multiple people can use the same computer (1)
Edit user permissions (1) so only specific users can securely access their storage space (1)
Control the amount of resources/storage each user can access (1) so the limited storage on the machine can be shared (1)
Enforce user permissions (1) so only certain users are allowed to install programs / access certain files (1) 

Data can be encoded using ASCII.
Describe ASCII.

A standard For representing text/characters
Allows data to be interchangeable between computers (from different manufacturers)
Each character is mapped to a unique number/binary
equivalent
ASCII (encoding) uses 7/8 bits
There are 128 unique characters (allow 256 for 128)

Explain one reason why files should be backed up regularly.

It helps prevent loss of data (1) because malware could deliberately delete data / because data can be
deleted/corrupted accidentally (1)
It helps minimise disruption following a system failure (1) because data can be restored (1)
Data can be restored (1) because physical hazards (fire/flood) (can damage storage devices) (1)

Give two pieces of information that organisations must tell people when requesting consent to use their personal data.

That they are giving consent
That they can say no / refuse
That they are not denied service, if they say no
What the data is being collected for
What processing will be done on their data/purpose of the processing/how data will be processed
That they can withdraw consent at any time
That the data will be shared (with third parties)
How long it will be stored
That the data will be stored securely

State two types of utility software.

Anti-virus
Anti-spyware
Firewall
File management
File repair/recovery
File conversion
Compression
Defragmentation
Back up

Explain one reason why compiled code helps protect intellectual property.

The source code is not available (1) because the compiler converts the code to machine code (1)
Compiled code is not human readable (1) so nobody else can alter it or sell it on (1)
Compiled code is difficult/impossible to reverse engineer (1) so nobody else can alter it or sell it on (1) 

Describe one freedom that open source software provides to developers.

Freedom to view the source code , modify it and redistribute it

Explain one positive impact of computing technology on the environment.

Less CO2 is produced by people travelling to work (1) because people can use the internet to work remotely (1)

More energy efficient homes (1) because smart technologies can switch the lights off when no one is in the room (1)
Endangered species can be protected (1) because GPS
technologies can track their locations

Describe how hardware and software work together to start a computer.

ROM contains (1) the firmware for the motherboard / BIOS / Boot sequence / Start-up instructions (1) that loads the operating system (1) from secondary storage (1) into RAM (1)

Describe the role of the transmission control protocol (TCP).

Splits the data into packets (1) and numbers them (1)
using a checksum (1) to see if packets have been delivered correctly (1) to avoid error/data corruption detection (1) before reordering them at their destination (1)
Award other linked points such as:
resends packets if found to be corrupt/missing on arrival (1)
handles handshaking and transmission details (1)
establishes a dedicated channel between source and destination devices (1)
communicates with the application layer above and the network layer below (1)

In system development testing is one of the critical stages. Give three reasons why testing phase is critical to system development

i) Verifies that the system works as intended and meets user requirements

ii) Detects bugs and errors early, reducing the cost and effort of fixing them later

iii) Helps identify vulnerabilities that could lead to security breach

iv) Ensures the system operates efficiently under different conditions

v)  Reduces maintenance costs

State three advantages of structured programs

Can be reused

minimize error

loaded efficiently

can be maintained and modified easily