AQA GCSE Level Computer Science Key Terminology

Central Processing Unit (CPU)

The main part of the computer, consisting of the registers, ALU and control unit.

Von Neumann architecture

Traditional computer architecture that forms the basis of most digital computer systems. Instructions are fetched, decoded and executed one at a time.

Fetch-decode-execute cycle

The complete process of retrieving an instruction from storage, decoding it and carrying it out. Also known as the instruction cycle.

Arithmetic Logic Unit (ALU)

Performs calculations and logical comparisons in the CPU.

Control Unit

Decodes instructions. Sends signals to control how data moves around the CPU.

Clock speed

Measured in hertz, the clock speed is the frequency at which the internal clock generates pulses. A higher clock rate means faster computer operations. The clock is the electronic unit that synchronises related components by generating pulses at a constant rate.

Processor cores

A part of a multi-core processor. A multi-core processor is a single component with two or more independent CPUs, responsible for the fetch-decode-execute cycle.

Cache

Memory in the processor that provides fast access to frequently used instructions and data.

Register

Tiny areas of extremely fast memory located in the CPU, designed for specific purposes where data or control information is stored temporarily.

Bus

A communication system that transfers data between components inside a computer.

Embedded system

A computer built to solve a highly specific problem. Not easy to change, examples include operating systems in washing machines, microwaves, or traffic lights.

Main memory (RAM)

Volatile and read-and-write memory used for temporary storage of currently executing instructions and data.

Random-Access Memory (RAM)

Volatile memory that loses data when the computer is powered off, used for temporary storage of executing instructions.

Read-Only Memory (ROM)

Non-volatile memory used to store startup instructions, which are retained when the computer is powered off.

Secondary storage

Permanent storage for instructions and data not currently in use by the processor.Stores the operating system, applications and data. Read-and-write and non-volatile.

Solid-state storage

Memory cards and SSDs, known for high portability and fast data access speed, with no moving parts. used in digital cameras and smartphones

Optical storage

Media such as CD-R and DVD-R used for music and files, has low capacity, slow access speed and is highly portable

Magnetic storage

Use of hard disk drives for the operating system and applications, known for high capacity but low portability.

Cloud storage

Remote servers that store data accessible over the internet, providing advantages like access and automatic backups.

Local storage

Any storage existing within the device you are working on, like a hard drive in a PC.

Network topology

The arrangement of elements in a communication network.

Personal Area Network (PAN)

A computer network for interconnecting devices centered on an individual person's workspace, typically using Bluetooth.

Local Area Network (LAN)

Networking within a small geographic area where all hardware is owned by the organization using it.

Wide Area Network (WAN)

Networking over a large geographic area that uses infrastructure hired from telecommunication companies.

Wired connections

Computer networks that connect hardware via physical cables.

Wireless connections

Computer networks that connect hardware via Wi-Fi.

Star network

Computers connected to a central switch where failure of one computer does not affect others.

Bus network

A LAN arrangement where each node is connected to a main cable called the bus.

Ethernet

Standard for networking local area networks using protocols, transmitting frames containing addresses and data.

Wi-Fi

Wireless connection requiring a wireless access point, sending data on specific frequencies.

Transmission Control Protocol (TCP)

Provides error-free transmission between two routers and is part of the TCP/IP protocol stack.

User Datagram Protocol (UDP)

A part of the Internet Protocol suite used for sending short messages called datagrams, known for being unreliable.

Internet Protocol (IP)

Routes packets across a wide area network and is part of the TCP/IP protocol stack.

Hypertext Transfer Protocol (HTTP)

Client-server method for requesting and delivering HTML web pages used for non-sensitive information.

Hypertext Transfer Protocol Secure (HTTPS)

Provides encryption and authentication for sensitive data transmitted over the web.

File Transfer Protocol (FTP)

Protocol used for sending files between computers, usually over a wide area network.

Simple Mail Transfer Protocol (SMTP)

Protocol used for sending email to an email server.

Internet Message Access Protocol (IMAP)

Used by mail clients to manage remote mailboxes and retrieve emails from servers.

Network security

A set of software policies and procedures that enhance and maintain the security of data on a network.

Authentication

The process of verifying a user's identity before granting system access.

Encryption

The process of converting data into a form that cannot be easily understood by unauthorized users.

Firewall

An application used within a network to prevent unauthorized access to a computer system.

MAC address filtering

Allows devices to access or block access to a network based on their physical address.

System Software

Software that manages the computer.

Application Software

Any program, routine or procedure that can be run on a computer system

Operating System

Specialised software that communicates with computer hardware to allow other programs to run

Utility Software

A program that performs a specific task relating to the operation of the computer 

Data Protection Act 2018

Legislation designed to protect individuals' personal data from unreasonable use.

Algorithm

A sequence of steps designed to perform a specific task.

Decomposition

Breaking down a complex problem into simpler parts for better understanding.

Abstraction

Removing all unnecessary details from a problem.

Program processes

Operations carried out by a computer that take inputs and produce outputs.

Algorithm efficiency

A measure of how well an algorithm performs its task based on speed and memory usage.

Linear search

A method of finding an item by examining each item sequentially until the target is found.

Binary search

An efficient search method for sorted files that focuses on the middle record. determining whether the target record has been found and, if not, whether the target record is before or after the mid-point. The process is repeated on the part of the file where the target record is expected to be until it is found

Merge sort

A divide-and-conquer algorithm that sorts lists by comparing and merging elements.the list is divided into the smallest unit, known as an element. Each element is compared with the adjacent list with a view to sorting the records and merging the two lists back together

Bubble sort

An inefficient sorting algorithm that compares adjacent elements.

Data type

Basic types provided by a programming language, such as char, integer, float, and Boolean.

Integer

A data type for storing whole numbers, both positive and negative.

Real/float

A data type used to store approximations of real numbers,

Boolean

Data type used to store logical conditions, such as TRUE/FALSE.

Character

A single alphanumeric character or symbol.

String

A sequence of alphanumeric characters or symbols.

Variable

A value that can change depending on conditions.

Constant

A value that cannot be changed during program execution.

Assignment

Assigning a value to a variable or constant.

Iteration

A programming construct that repeats code a specified number of times based on conditions.

Selection

Instructions that evaluate a Boolean expression and branch to alternatives.

Sequence

Instructions carried out one after the other in order.

Subroutine

A block of code with a unique name that supports code reuse.

Procedure

A named block of code that can take parameters and perform tasks.

Function

A named block of code that returns a value and can take parameters.

Count-controlled loop

An iteration that loops a fixed number of times based on a counter.

Condition-controlled loop

An iteration that repeats based on conditions set by the programmer or program.

Mathematical operator: DIV

Outputs the number of times one number fits into another (integer division).

Mathematical operator: MOD

Outputs the remainder left over from integer division.

Boolean operator: AND

Returns TRUE only if both compared values are TRUE.

Boolean operator: OR

Returns TRUE if at least one compared value is TRUE.

Boolean operator: NOT

Returns the opposite of the input value.

Authentication routines

A piece of code that checks if someone is allowed to access a system/program and what level of access they should have

Test data: Normal/typical

Data supplied to a program that is expected.

Test data: Boundary/extreme

Data supplied to a program designed to test the boundaries of a problem.

Test data: Erroneous

Data of the incorrect type that should be rejected. 

Syntax Error

An error that breaks the grammatical rules of a programming language and stops it from running

Logic Error

“The program runs but does not produce the expected output.

Logic gate: AND

Accepts two inputs and produces TRUE output only if both inputs are TRUE.

Logic gate: NOT

Accepts one input, producing FALSE if TRUE and vice versa.

Logic gate: OR

Accepts two inputs, producing TRUE output if at least one input is TRUE.

Logic gate: XOR

Produces TRUE output if one input is TRUE and the other is FALSE.

Low-level language

Programming language that is close to machine code.

Machine code

The actual binary code executed by a specific processor architecture.

Assembly language

Language closely related to machine code used for programming.

Translator

Converts a program from one programming language to another.

Interpreter

Translates and executes code one statement at a time.

Compiler

Translates high-level programming language to machine code.

Assembler

Converts assembly language into machine code.

Bit

The smallest unit of data in a computer, representing a binary 0 or 1.

Nibble

Half a byte, consisting of four bits.

Byte

A collection of eight bits.

Kilobyte (KB)

A measure of data equal to 1000 bytes.