method of transmission e.g

• blue tooth
• radio
• optical
• satellite
• infra-red
• microwave

device e.g.

• 3G (WAP) mobile phones/mobile phones/cell phone/remote
• key pad/remote control/keyboard
• infra-red mouse
• multimedia mobile handsets/notebooks
• GPRS (general packet radio service) mobiles
• WLAN(or WiFi) hotspots sited in public areas - e.g. coffee
• shops, railway stations, airports, motorway services
• linked printers
• PDA's (personal digital assistants)
• GPS

(a) Defragmentation software   -   Reorganises files on a disk to improve efficiency

(b) Disk contents analysis/repair software - Scans a hard disk to identify bad sectors

(c) Disk formatter -  Prepares a hard disk for first use

• memory used up/slows down computer/alters setting/systems failure
• erases files/erases data/corrupts data/data needs restoring
• infects other computers on the network
• production loss/financial loss

• Distributed data processing is where computers located in physically separate location transmit data after processing to a server computer that updates the master file. Time-sharing on the other hand is where various terminals transmit data to be processed by a central computer's CPU. Each terminal's tasks are allocated a time slice of the CPU

• Radio waves
• Microwaves
• Infrared waves

– if one station/cable fails, others are not affected
– easier to identify faults when using star topologies
– it is easier to expand this type of network
– performance doesn’t deteriorate under load

• It prevents double-booking which could happen in paper-based booking system
• The customer gets immediate feedback on the availability of seats
• The customer can make  booking at any time of the day
• Emails provided by customers during booking can be used by companies for advertisement

Dual input of data

• Two inputs are compared by the system and any discrepancies are reported (and not stored.)
• Data input once, either printed out or checked on the screen and  errors corrected

 Rules are given to the processor

• Only accept A, B, C, D, E, F, G i.e Any other input rejected.

Drop-down list/radio buttons

• Provides only valid inputs, so no other validation is required

• used to identify a device
• it is a unique (address)
• it is a static address // it does not change
• it is set by the manufacturer
• the first part is the manufacturer ID/number / identifies the manufacturer
• the second part is the serial number / ID.

Network Failure - when the network becomes faulty or the network is down, users may not access network resources hence operations of an organization may be brought to a standstill

Security Issues:  A computer network can be accessed thus there is an increased chance of hacking

The rapid spread of viruses: Viruses can easily spread to terminals of a computer network which may be very expensive to clear

Cultural and moral effects: adult content may be shared in a networked environment which may be of negative impact on teenagers

• It can now process two instructions simultaneously (where suitable) increasing the performance.

• Firmware is a software program permanently etched into a hardware device such as a keyboards, hard drive, BIOS, or video cards.
• Device drivers are operating system-specific and hardware-dependent. A device driver acts as a translator between the hardware device and the programs or operating systems that use it. 
• Firmware is a software that controls a system, and firmware's functionality ranges from performing basic tasks like minimal I/O controls to full-fledged software system running with simple or no OS, with scheduler, memory management, etc. 
• A driver, on the other hand, is usually part of the operating system that performs the specific task of controlling a hardware component like a display or USB controller, etc., and gives an interface to use the hardware by Operating system and applications.

• Thesaurus - Is a feature in a word processor that suggest words with the similar or opposite meaning to the one selected
• Comments: a feature in a word processor that allows a user to attach a remark about the selection

• user changes his mind
• new government legalisation/company policy company changes
• changes in hardware
• changes in software/upgrades/new versions
• improved operating efficiency/ease of use

• Radiowaves are omnidirectional while microwaves propagate in one direction at a time(unidirectional)
• Radiowaves can be propagated over long distances through sky mode while microwaves require a relay satellite to amplify and retransmit the microwaves signals to the receiver earth station

Advantages of  of Hard Disk Drive

• Hard disk drives are cheaper per gigabyte than solid state drives.
• Hard disks have a longer lifespan than solid state drives

Disadvantages of Hard Disk Drives

• Consumes more power than SDD
• They are noisy.
• They are slower than solid state drives.
• They are susceptible to wear and tear as they have movable parts.

Advantages of Solid State Drives

• Are faster than HDDs
• It is more durable as it does not have moving parts
• Consumes less power
• Are not noisy

Disadvantages of SDD

• It costs more than a conventional hard disk
• Have fewer write/erase cycles compared to a hard disk drive
• Lost data cannot not be recovered

• connects different networks
• transfer data packets from source to destination
• allow hosts on different networks to communicate

(i) State the name of this protocol.   HTTPS 

(ii) Identify how this protocol changes the data to transmit the data securely.

• It encrypts it
• It applies encryption algorithm
• It applies an encryption key

State the characteristics of each of the following network topologies (KCSE COMPUTER STUDIES 2021 )

i) Mesh Topology  (2mks)

• a host/node is connected to one or multiple hosts
• a   host/node in point to point connection with every other host or a few hosts
• hosts/nodes in mesh topology also work as relays for other hosts which do not have point-to-point links

(ii) Ring Topology (2mks)

• each host/node connects exactly to two other hosts
• data travels around the ring in one direction through all intermediate hosts
• failure of any host results in the failure of the whole ring

A backup is a copy of data that can be used if the original data is lost.