Computer Science Revision Guide: Architecture, Data, and Networks

Comprehensive vocabulary flashcards covering computer architecture, data representation, networking, hardware, and logic operations from the Computer Science Revision Guide.

Bit

A single binary digit with a value of either $0$ or $1$.

Byte

A collection of $8$ bits treated and processed as a single unit.

Nibble

A group of $4$ bits, exactly equal to one hexadecimal digit.

Binary Coded Decimal (BCD)

A number representation system based on denary (base $10$ in binary) where each decimal digit is encoded into its own $4$-bit nibble with place values $8, 4, 2, 1$.

Kibi (Ki)

A binary prefix denoting a multiplication factor of $2^{10} = 1024$.

One's Complement

A binary operation performed by flipping every individual bit (subtracting each bit from $1$).

Two's Complement

A method for representing negative integers in binary, obtained by taking the one's complement and adding $1$.

Overflow

A condition occurring when the numerical result of a calculation is too large to fit within the designated number of bits available for storage.

ASCII

A $7$-bit character encoding standard representing $128$ characters, including letters, digits, symbols, and control codes.

Unicode

A $16$-bit or $32$-bit character encoding standard that represents over $1$ million characters across world languages and emoji, matching ASCII in its first $128$ codes.

Pixel

The smallest individual element of a bitmap graphic, defined by its position in the matrix and its colour value.

Colour Depth

The number of bits assigned to encode the colour of each individual pixel in an image (for example, $1\text{ bit} = 2$ colours, $8\text{ bits} = 256$ colours, $24\text{ bits} = 16.7\text{ million}$ colours).

Image Resolution

The total dimensions of a bitmap graphic specified as $\text{width} \times \text{height}$ in pixels.

Vector Graphic

An image format constructed from drawing objects defined by geometric formulae and properties stored in a drawing list, which scales without quality loss.

File Header

Metadata stored at the beginning of an image file containing essential properties such as file size, resolution, and colour depth.

Analogue Data

Data measured directly from a physical property that can take any value across a continuous range.

Digital Data

Data represented and stored as binary values selected from a discrete range.

Sampling

The process of measuring the amplitude of an analogue sound wave at regular time intervals and storing each recorded value in binary format.

Sampling Rate

The number of audio samples captured per second, expressed in Hertz ($\text{Hz}$).

Sampling Resolution (Bit Depth)

The number of bits allocated to each audio sample, where $16$ bits provides $65\,536$ amplitude levels.

Lossless Compression

A compression technique in which file size is reduced without losing any data, allowing the original file to be reconstructed exactly.

Run-Length Encoding (RLE)

A lossless compression algorithm that replaces consecutive repeating values with the value itself and a counter of how many times it repeats.

Lossy Compression

A compression technique that achieves significantly smaller file sizes by permanently removing data and detail that humans are unlikely to perceive.

Local Area Network (LAN)

A network spanning a restricted geographical area such as a single room, building, or site, with infrastructure owned entirely by the organisation.

Wide Area Network (WAN)

A network that connects geographically dispersed sites many kilometres apart, relying on leased telecommunication lines or public networks such as the Internet.

Thin Client

A client terminal designed solely for user input and output, relying entirely on a central server to perform computational processing.

Thick Client

A networked computer that possesses independent processing capability and performs computational operations locally.

Bus Topology

A network layout where all nodes connect to a single central shared cable terminated at both ends, making it cheap but prone to total failure if broken.

Star Topology

A network layout where all devices connect individually to a central switch, isolating cable faults but leaving the switch as a single point of failure.

Mesh Topology

A highly reliable network layout where each device interconnects directly to multiple other devices, providing alternative routing paths.

Network Interface Card (NIC)

A hardware component that enables a device to connect to a network and assigns it a unique physical MAC address.

Switch

A networking device that inspects data packets and directs them exclusively to the specific intended recipient device.

Router

A networking device that links separate networks together and forwards data packets across them according to destination IP addresses.

World Wide Web

An information system of interconnected HTML pages identified by URLs and retrieved across the Internet using HTTP.

Domain Name Service (DNS)

An Internet service that receives a domain name from a browser, resolves it, and returns the corresponding numerical IP address.

RAM (Random Access Memory)

Volatile primary storage that allows read and write operations, holding currently active program code and operational data.

ROM (Read Only Memory)

Non-volatile primary storage that cannot be modified under normal operations, used to retain permanent firmware and the bootstrap loader (BIOS).

Cache

A small, high-speed memory unit placed in close physical proximity to the processor to hold frequently requested instructions and data.

Buffer

A temporary memory space acting as a queue to compensate for speed disparities when transferring data between a fast and a slow device.

Sensor

An input hardware device that detects and measures an external physical parameter, converting it into a signal for computer input.

Actuator

An output hardware mechanism that takes an electrical control signal and produces physical movement or adjustments (e.g., operating a motor, valve, or heater).

Logic Proposition

A declarative statement that is strictly evaluated to be either TRUE or FALSE.

XOR Gate

An exclusive logic gate whose output is $1$ if and only if its two inputs are different ($X = A \oplus B$).

Von Neumann Architecture

A theoretical computer design centered on a single CPU that sequentially fetches and executes instructions from a shared memory holding both program code and data.

Control Unit (CU)

The central processor component responsible for decoding instructions and synchronizing operations across system buses by issuing timing signals aligned with the clock.

Arithmetic Logic Unit (ALU)

The internal CPU component that executes all elementary mathematical calculations and logical evaluations.

Program Counter (PC)

A dedicated CPU register that stores the memory address of the next sequential instruction waiting to be fetched.

Memory Address Register (MAR)

A processor register that holds the memory address of the specific storage location about to be accessed for reading or writing.

Memory Data Register (MDR)

A processor register that buffers data newly retrieved from main memory or prepared to be written out to memory.

Current Instruction Register (CIR)

A CPU register that stores the binary machine code of the instruction currently undergoing decoding and execution.

Accumulator (ACC)

A central working register within the processor that holds immediate operands and results produced by the Arithmetic Logic Unit.

Index Register (IX)

A special-purpose CPU register containing an offset value that is automatically added to a base memory address during indexed addressing.

Status Register (SR)

A CPU register consisting of individual flag bits indicating arithmetic conditions such as carry, overflow, negative, and zero.