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

Taking a four-digit 0  binary number i.e (0000)2

In ones complement this is  1111

In twos complement this becomes 1111+1= 0000

So, It is clear that 0 and negative zero is the same in twos complement while in ones complement they are two different values

• compact disks
• DVDs
• Blue Ray

• Authenticity
• Users' needs
• Availability of documentation
• Cost
• Compatibility
• Upgradability
• Portability

(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

• Power surge/loss (damages hardware)
•  Use a UPS
• Water can be spilt on the device
• Don’t have water near the device
• Keep the device in a waterproof box when not is use
• Fire can destroy the device
• Use electrics safety
• Keep the device in a fireproof box when not in use
• Data is accidentally deleted
•  Add verification method for data deletion
•  Set access levels for data to limit who can delete the data
• Incorrect use of storage device
• Making sure the device is ejected before removing
•  Physical damage to hardware // hardware failure
•  Correct care and maintenance of hardware
•  Software failure 
• Making sure it is always up to date // enable automatic updates

• More RAM will improve the performance of the computer 
• More RAM will speed up the access to data
• Excessive use of VM can cause disk thrashing which decreases performance
• VM is slower to access than RAM direct (because it has to go back to RAM first)
• Moving data between RAM and VM takes processor time

• The user can access the source code  so, they can tailor the software to their needs and they can fix any bugs in it
• the source code could be studied for educational purposes
• The user can redistribute the software/program  but this must be done under the same terms as the original software

(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

• the computer appears to “freeze”/”hang”
• computer won’t respond
• failure of hardware (stops computer normal functioning)
• failure of software (stops computer normal functioning)

Responsibilities of the software developer is to ensure that the ergonomics focuses on making software user-friendly, reduces repetitive motions or eyestrain and enables movements of users to promote comfort and efficiency.

Software can be designed with adjustable text sizes and screen brightness settings to prevent eye strain, offering users a way to customise their visual experience for better comfort during prolonged use.

Define the term internet      1mk

• The global interconnection of computer networks for purpose of communication and resource sharing

Explain the term web page    1mk

• A hypertext  page prepared to display the content on the web

Explain the following internet address http://www.google.co.us in reference to the structure of a URL    3mks

• HTTP- hypertext transfer protocol or simply protocol
• WWW – subdomain
• google – the name of the computer with the web content/domain name
• .co – top level domain for commercial organization
• .us- a TLD extension for the country US

What is the world wide web                                       1mk

•  A virtual space on the internet that allows web pages and sites to be accessed

Define the term browser                                    1mk

•  A software that used viewing of web content

Explain the meaning of the word hyperlink     1mk

• A text or picture that is a link to another webpage on the internet

What is a search engine?     1mk

• Is a special program that collects and stores links to information websites allowing users to search its database for them
• A specialized web-based application that help the user to search for specific information on the internet.

Explain the meaning of the term internet service provider            1mk

• A company that offers internet services to end-users

Identify three elements apart from a computer that is required for one to be connected to the internet    3mk

• Modem
• Internet software
• Internet service provider
• Telecommunication lines
• TCP/IP protocols

Define the term modem 1mk

• Stands for modulator-demodulator
• A device that enables telecommunication to use telephone lines

What is a protocol? Write the following in full: TCP/IP, HTML, HTTP and FTP           5mks

• Protocols – are special communication rules that govern sending and receiving of messages by computers on a network
• Html – hypertext markup language
• Hypertext transfer protocol
• Transmission Control Protocol
• Internet Protocol
• File Transfer Protocol

What would you do if a website refused to load on the browser within the first attempt?   1mk

• Click the refresh button on the toolbar

 State three internet services                         3mks

• Instant messaging
• E-mails
• E-commerce
• Social media and networks
• E-learning

Define the term internet telephony      1mk

• Transmission of voice data over the internet

State three benefits of the internet in our society

• Provides a platform for conducting business and marketing
• Provides many platforms such as social media through which people can contact each other
• Cost saving
• Efficient communication

Syntax errors-Incorrect use of programming language

Logical errors- The program do not give the expected output

Runtime errors- Premature end of a program

• Detecting congestion.
• Synchronizing activity between traffic lights.
• Updating traffic light timing in real time.
• Updating and informing drivers of ideal speeds.
•  Prioritizing transportation flow.
•  Reduce congestion and time spent on the road
• By reducing congestion it will decrease pollution
• Prioritize traffic based on changes in traffic conditions in real time.
• This system is also helpful to reduce infrastructure damage. It is possible to identify overloaded vehicles and provide them with appropriate ways or roads, which will reduce road damage.

• RAID 10 is a combination of RAID 0 (zero) and RAID 1 (one)

• camera
• microwave
• washing machine
• video recorder
• fridge
• sewing machine
• air conditioning
• games console
• electronic game electronic toys
• rice cooker
• dish washer
• TV
• alarm clock
• radio

• Real-time processing is where data is processed as it is received and the output is made available immediately to influence the ongoing activity
• Interactive processing is computer processing in which the user can modify the operations appropriately while observing results at critical steps

• 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

Many components that go into computer systems are toxic and dangerous to the environment if released or disposed of inappropriately.
Heavy metals are used in batteries and circuits and these can pollute groundwater or kill animals if left exposed on landfill. Large quantities of plastics are used in systems, which take a long time to break down, some of the plastic will eventually break down into toxins as it degrades.

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