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.

• hexadecimal is easier (for humans) to read (than binary);
• numbers are displayed in a more compact way (in hexadecimal than in binary);
• it is quicker to type in (hexadecimal numbers than binary numbers);
• it reduces the risk of typing errors (in hexadecimal numbers than binary numbers);

• A physical file contains the original data whereas a logical file does not contain any data
• A physical file contains one record format while a logical file can contain up to 32 record formats
• A physical file can exist without a logical file while a logical file cannot exist without a physical file

1. Hardware failure
2. Corrupted software files
3. Hacking into the system
4. Power failure

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

• TV remote control communication;
• DVD remote communication
• Communication between peripheral devices and the computer
• Data link over a short distance using mobile phones Radio remote control
• Remote locking/opening doors/ devices

• a computer that responds to requests to provide information and services over the Internet - an Internet server
• defines how messages are transmitted and formatted over the Internet-HTTP
• software that enables users to access/view documents and other resources on the Internet - Browser     
• numerical ID for each device on the Internet-IP address
• unique ID for a network interface card  -MAC address

(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

• Use of debugging utilities
• Use of test data
• Dry run / Desk checking

Number of cores
The number of cores a processor has directly affects the performance of the processor. Each core can perform its own fetch-execute cycle independently of others, so different applications can be allocated to different cores. Quad-core (four-core) and even octa-core (eight-core) processors are becoming common

Cache memory
A processor’s cache is a small portion of incredibly fast memory. It has read and write speeds far higher than hard disk drives and even SSDs. The cache is used to store frequently used information and reduces time wasted in fetching the same information from main memory time and time again

Clock speed
A processor’s clock speed relates to the frequency of the pulses generated by the system clock. The higher the frequency, the more cycles of the fetch-execute cycle can be completed in the same period of time.

Word length
A word is a group of bits that is treated as a single unit by a processor. Words can be used for representing both instructions and data. The length of a word is the number of bits that are assigned to it, with higher word lengths allowing for more bits to be transferred and manipulated as a single unit.

Address bus width
The width of a bus relates to the number wires that make up the bus. Increasing the width of the address bus increases the range of addresses that it can specify, hence increasing the computer’s amount of addressable memory. Adding a single wire doubles the number of addressable memory locations

Data bus width
Increasing the width of the data bus increases the volume of data that can be transferred over the bus at any one time. A wider data bus allows the processor to fetch more data from the main memory in one cycle of the fetch-execute cycle, reducing the number of cycles required to fetch large volumes of data.

Syntax error

• An error in the source code of a program like pront("Hello, " + name) instead of print
• These are errors that emanate from improper use of language rules such as spelling mistakes,improper use of variables and misuse of reserved words

Logical error

• A mistake in a program's source code that results in incorrect or unexpected behaviour like if age == 65: print("Eligible for a discount.") instead of using if age >= 65: print("Eligible for a discount.")
• These are errors that occur due to imperfect comparisons

Run-time error

• An error which occurs when a program is asked to do something that it cannot, resulting in a ' crash'9. For example, asking a number to be divided by 0 such as 72/0.
• An error that results in a sudden halt of an executing program

Explain the purpose of each of the following features of a spreadsheet chart (KCSE 2021, Q19 (a))

Legend

• Legends are a small visual representation of the chart's data series to understand each without confusion.

A data series

• is a row or column of numbers that are entered in a worksheet and plotted in your chart, such as a list of quarterly business profits
• A group of related data points or markers that are plotted in charts and graphs

Data Marker

• A symbol on the chart that represents a single value in the worksheet.
• A column, dot, pie slice, or another symbol in the chart representing a data value

https://www.lifewire.com/data-series-data-points-data-labels-3123411

Benefits

• The user is not restricted to the predetermined options//the GUI uses icons and set menus
• The user has more control over the computer settings//in GUI computer settings are protected from the user
• Uses less memory than GUI
• Requires less processing power for the interface
• More processing power is made available for the task

Drawbacks

• The commands used have to be learnt
• The commands used have to be remembered
• The commands used have to be typed in/entered exactly
• Have to remember the exact path/correct name of application
• More prone to errors on data entry Commands have to be typed in//in a GUI can use touchscreens/mice
• Tends to be used by specialist people//GUI is more user-friendly and can be used by non-experts

(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

Microwaves can cover shorter distances. On the contrary, radio waves can travel a long distance. Radio wave is usually propagated through sky mode while microwave uses the line of sight propagation. 

i) To manage the execution of instructions
By running a clock
To decode instructions
(ii) To store OS
To store those parts of applications programs currently running
To store data currently in use
(iii) Part of the processor where data is processed/manipulated
All I/O must pass through here

• Implementation

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

• Portable
• Light
• Faster access speed
• No moving parts
• Efficient power consumption
• Durable
• Small physical size
• Large storage capacity

• 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.