COMPUTER SCIENCE (1)

Chapter 1-5 (paper 1 SE midterms)

Character Set

A defined list of characters that a computer can recognise and use, each mapped to a unique, numerical binary code.

ASCII

An early character encoding method, primarily used for English text.

Unicode

A character encoding standard designed to represent text in all of the world's languages, including non-English alphabets and emojis (more bits per character than ASCII).

Pixel

Short for "picture element," a single point in an image.

Resolution

The number of pixels in an image (width x height).

Colour Depth

The number of bits used to represent the colour of each pixel in an image.

Metadata (Images)

Data about an image such as

Analogue Sound

Sound that is continuous and varying in amplitude and frequency, found in the real world.

Sample (Sound)

A measure of the amplitude of an analogue sound wave taken at a specific point in time during the digital conversion process.

Sampling Rate (Sound)

The number of samples taken per second when converting analogue sound to digital, measured in hertz (Hz).

Sample Resolution (Sound)

The number of bits used to store the amplitude of each sample when converting analogue sound to digital.

Bit

The fundamental unit of information, representing either a 0 or a 1.

Nibble

A group of 4 bits or half a byte

Byte

A group of 8 bits.

Kibibyte (KiB)

1024 bytes.

Mebibyte (MiB)

1024 KiB.

Gibibyte (GiB)

1024 MiB.

Tebibyte (TiB)

1024 GiB.

Pebibyte (PiB)

1024 TiB.

Exbibyte (EiB)

1024 PiB.

Data Compression

The process of encoding information using fewer bits than the original representation, to save storage space or reduce transmission time.

Lossy Compression

A form of compression where some information is lost in the process of reducing the file’s size.

Lossless Compression

A form of compression where all original information is retained.

Run Length Encoding (RLE)

A form of data compression that reduces the physical size of a repeating string of characters, by storing the character and the number of times it repeats.

Data Transmission

The process of sending data from one device to another, often by breaking it into smaller packets.

Packet

A small unit of data used in transmission, containing a header, payload, and trailer.

Packet Header

Part of a packet that contains control information such as the destination address, originator's address, and packet number.

Payload

The main content or actual data being sent in a packet.

Trailer

The part of a packet that contains error-checking information to verify data integrity.

Destination address

An IP address that specifies where a packet is going.

Packet number

A sequential identifier assigned to each packet, used to reorder them at the destination.

Destination address

An IP address that specifies where a packet came from.

Packet Switching

A method of data transmission where data is split into packets, sent separately via the most efficient routes, and reordered at the destination.

Serial Transmission

A method of data transmission where bits are sent one after another over a single wire or channel.

Parallel Transmission

A method of data transmission where multiple bits are sent at the same time using multiple wires or channels.

Simplex Transmission

A one-way communication method where data flows in only one direction.

Half-Duplex Transmission

A two-way communication method where data flows in both directions, but only one direction at a time.

Full-Duplex Transmission

A two-way communication method where data flows in both directions at the same time.

Universal Serial Bus (USB)

A standard interface that connects peripheral devices to a computer, using serial transmission and allowing data and power transfer.

Parity Check

An error detection method that uses a parity bit to ensure the number of 1s in a data transmission matches the expected even or odd total.

Even Parity

A parity system where the number of 1s in the data, including the parity bit, must be even.

Odd Parity

A parity system where the number of 1s in the data, including the parity bit, must be odd.

Checksum

An error detection method that uses a calculated value based on the data, which is appended and checked at the destination.

Echo Check

An error detection method where the receiver sends the received data back to the sender, who compares it to the original.

Check Digit

A form of checksum where a single digit, calculated from the data, is added to detect errors in data like ISBNs or barcodes.

Automatic Repeat Query (ARQ)

An error control method where data is resent automatically if an error is detected or no acknowledgment is received within a set time.

Encryption

The process of converting plaintext into unreadable ciphertext to protect data from unauthorised access during storage or transmission.

Plaintext

The original readable data before encryption.

Ciphertext

The unreadable form of data after encryption, which requires a key to decrypt.

Symmetric Encryption

An encryption method where the same private key is used by both sender and receiver to encrypt and decrypt data.

Asymmetric Encryption

An encryption method that uses a public key for encryption and a private key for decryption, allowing secure communication without sharing secret keys.

Central Processing Unit (CPU)

The hardware component within a computer that carries out the instructions of a computer program.

Microprocessor

A type of integrated circuit that contains the CPU (and sometimes other components) on a single chip.

Arithmetic Logic Unit (ALU)

A component within the CPU responsible for performing arithmetic operations (addition, subtraction, etc.) and logical operations (AND, OR, NOT).

Control Unit (CU)

A component within the CPU that manages and coordinates the other components of the computer, fetching and decoding instructions.

Register

A small, very fast storage location within the CPU that holds data temporarily during processing.

Program Counter (PC)

A register that stores the address of the next instruction to be fetched from memory. It increments during each fetch-execute cycle to point to the next instruction.

Memory Address Register (MAR)

A register that stores the address to fetch data from or the address where the data is to be stored.

Memory Data Register (MDR)

A register that stores the data that is being fetched from or written to memory. It acts as a buffer between main memory and the CPU.

Accumulator (ACC)

A register that stores the results of calculations or operations carried out by the Arithmetic Logic Unit (ALU). Also temporarily holds data being processed.

Fetch-Decode-Execute Cycle

The fundamental process by which the CPU continually retrieves instructions stored in main memory and decodes and executes them.

Clock Speed

The rate at which a CPU executes instructions, measured in Hertz (Hz), which affects CPU performance.

Number of Processor Cores

The number of independent processing units within a single CPU, allowing for parallel execution of tasks and affecting performance.

Cache

A small, fast memory device located on the CPU that stores frequently used data and instructions, providing faster access than main memory.

Cache Size

The amount of fast, temporary memory (cache) available to the CPU, which stores frequently accessed data for quicker retrieval and affects performance.

Embedded System

A computer system with a simple, dedicated function within a larger mechanical or electronic system (e.g., in a washing machine or car).

Instruction Set

A collection of all the commands (instructions) that a processor can understand and execute, written in machine code.

Barcode scanner

An input device that reads barcodes and converts them into digital data, allowing quick and unique identification of products.

Digital camera

An input device that captures photographs or videos as digital files, used to input images into a computer system.

Keyboard

An input device with keys that allows text, numbers, and commands to be entered into a computer.

Microphone

An input device that captures analogue sound and converts it into a digital signal for voice or audio input.

Optical mouse

An input device that detects movement and clicks to control a pointer on a screen for navigation and interaction.

QR code scanner

An input device that reads QR codes and converts them into readable digital data, such as URLs or payment information.

Touch screen (resistive)

A screen that registers touch through pressure on two layers, allowing input by finger or stylus even with gloves.

Touch screen (capacitive)

A screen that registers touch using the electrical properties of the finger for more accurate and responsive input.

Touch screen (infra-red)

A screen that uses a grid of infrared beams to detect touch location and can detect any input object.

2D scanner

An input device that captures flat images or documents as digital files, used to digitize physical documents.

3D scanner

An input device that captures the shape and appearance of 3D objects to create digital 3D models. Often achieved by taking several pictures from multiple angles.

Actuator

An output device that produces physical movement, converting digital signals into real-world mechanical actions.

Digital Light Processing (DLP) projector

An output device that projects images onto a surface using tiny mirrors and light, for large visual displays.

Inkjet printer

An output device that sprays tiny drops of ink onto paper to produce colour or black-and-white printed images and text.

Laser printer

An output device that uses lasers and toner to produce high-speed, high-quality printed output efficiently.

Light Emitting Diode (LED) screen

A display that uses LEDs to show images with bright and energy-efficient lighting.

Liquid Crystal Display (LCD) projector

An output device that projects images using a light source and liquid crystal panels for visual presentations.

Liquid Crystal Display (LCD) screen

An output display that uses liquid crystals and a backlight to show images with low power consumption.

Speaker

An output device that converts digital audio signals into analogue sound output like music, voice, or alerts.

3D printer

An output device that builds physical objects layer by layer from digital 3D models using materials like plastic or resin.

Sensor

A device that detects physical inputs from the environment (e.g. temperature, light, motion and pressure) and converts them into electrical signals.

Acoustic sensor

A sensor that detects sound or vibrations and measures sound levels.

Accelerometer

A sensor that measures acceleration, movement, or tilt, capturing motion or orientation data.

Flow sensor

A sensor that measures the flow rate of liquids or gases.

Gas sensor

A sensor that detects the presence or concentration of gases in the environment.

Humidity sensor

A sensor that measures the moisture level in the air.

Infra-red sensor

A sensor that detects infrared radiation to measure heat, motion, or proximity.

Level sensor

A sensor that measures the level of liquids or solids in containers.

Light sensor

A sensor that measures the intensity of light.

Magnetic field sensor

A sensor that detects magnetic fields or changes in magnetism.

Moisture sensor

A sensor that detects moisture content in soil or materials.

pH sensor

A sensor that measures the acidity or alkalinity of a solution.

Pressure sensor

A sensor that detects the force applied by gases or liquids over an area.