AQA Computer Science Definitions

Hardware

The physical components making up a computer system eg: Motherboard, RAM, Keyboard

Software

The computer code, programs and algorithms that gives instructions to the hardware, to perform the required task

Computer

A computer is an electronic device that processes data by following a set of instructions

System Software

System software manages the computer system resources and acts as a platform to run application software

Application Software

Application software is software that performs end-user tasks.

Operating System

An operating system is a collection of software used to manage the computer resources and application software that runs on top of it.

Utility Software

Software provided by the operating system that is not essential for the computer, but makes managing the tasks of operating system a lot easier.

Encryption Software

Software that uses an algorithm and encryption key to transform plain text data into ciphertext data.

High Level Languages

Languages which use English-like syntax but must be translated to machine code to be executed.

Low Level Languages

Low-level languages are those that sit close to the computer's instruction set.

Instruction Set

Instruction set of a processor is the list of all the software instructions that the processor can execute.

Translator

A program that converts source code into machine code so that a computer can understand and execute it.

Compiler

A compiler translates all the original program code before execution, it takes the entire high-level program as input and produces machine code.

Interpreter

Interpreters do not generate machine code directly; they read a high-level program line-by-line and call corresponding subroutines.

Assembly Language

Each line of assembly language is assembled into a single machine code instruction.

Assembler

A translator which translates each line of Assembly Language directly into machine code.

Machine Code

Machine code is the binary instructions that a computer or microprocessor can understand.

Computer Programme

A computer program is a list of instructions that the CPU can use to carry out a particular task.

Memory

Storage on a computer comes in many different types with different purposes and attributes.

Main Memory

RAM and ROM memory.

Secondary Memory

Permanent storage on the computer.

CPU

Central Processing Unit. A CPU processor fetches, decodes and executes instructions from memory and performs logical and arithmetic operations.

ALU

Arithmetic Logic Unit. Performs arithmetic and logic operations and is situated in the CPU.

Control Unit

Purpose of the control unit is to decode the machine code instruction.

Clock

The purpose is to keep all the processor components synchronised.

Register

Memory locations on the CPU, much faster than cache and RAM, used to store frequently accessed data and instructions.

Bus

Wires through which data and instructions are transferred between computer components.

Processor

A processor fetches, decodes and executes instructions from memory and performs logical and arithmetic operations.

Core

A core is CPU in its own right.

Cache

Cache is a volatile memory store on the processor, and is not to be confused with RAM and registers.

RAM

Random Access Memory - Memory which can be accessed by the CPU.

ROM

Read Only Memory - computer memory which stores instructions which cannot easily be modified.

Volatile Memory

A type of memory which stores data only while it has power.

Non-Volatile Memory

A type of memory which persists in storing data once power is lost.

Solid State Drive

SSD - Fast secondary storage which uses transistors to store binary values.

Magnetic Storage

HDD - magnetic persistent storage.

Tiny magnetics

Represent binary values depending on their charge.

Optical Storage

CD/DVD/Blu-Ray - use of laser to read reflected light from the surface of the disc to represent binary values.

Cloud Storage

Cloud computing is storing data online.

Local Storage

Memory on the computer not transferred online.

Embedded System

A computer with a dedicated / specific purpose or function.

Cloud Computing

Cloud computing is storing and using services online.

Computer Network

Two or more computer devices linked together to communicate and share resources and data.

Wired Network

A network of computers using ethernet cables, Fibre optic cables.

Wireless Network

Sending data over radiowaves.

WAN

Wide Area Network - interconnected networks, internet is an example.

LAN

Local Area Network - network of computers usually within an organisation or university.

PAN

Personal Area Network e.g.: A phone and headphones connected via Bluetooth.

Router

Directs data packets across a wide area network.

Switch

Directs data packets across a Local area network.

MAC

Media Address Control address, a fixed identifier for each device, assigned by the manufacturer.

NIC

Network interface card - part of a device which allows connection either via WiFi or Ethernet.

Internet

A world-wide system of computer networks.

World Wide Web

The World Wide Web is the combination of all resources and users on the Internet that are using the Hypertext Transfer Protocol (HTTP/HTTPS).

Bus Network

A historic means of connecting computers to a main cable (bus or backbone cable). All computers share this cable to transmit data to each other.

Star Network

All the devices have their own cable connecting them to a switch, controlled by a server with client computers.

Protocol

A set of rules to determine how data is managed and transmitted across a network.

TCP

Transmission Control Protocol.

IP

Internet Protocol.

HTTP

Hypertext Transfer Protocol.

HTTPS

Hypertext Transfer Protocol Secure.

FTP

File Transfer Protocol.

IMAP

Internet Messaging Protocol.

SMTP

Simple Mail Transfer Protocol.

UDP

User Datagram Protocol.

Ethernet

A family of related protocols, used to communicate between devices.

WIFI

A family of related protocols, used to communicate wirelessly between devices.

Latency

The amount of time when sending and receiving data.

Cyber Security

The processes, practices and technologies designed to protect devices, data and networks from malicious attacks.

Social Engineering

Manipulating or fooling people into revealing confidential information such as login details or bank details.

Malware

Malicious Software.

Data Structure

A structured collection of data e.g.: List, Array, Database, Record.

Structured Data

Data that is organised so it is easy to update, delete, search and maintain.

Unstructured Data

An unorganised collection of data.

Database

A structured collection of data e.g.: List, Array, Database, Record.

Flat file Database

A single table to record all data.

Relational Database

A structured collection of data with two or more tables linked by shared keys.

Table

A single structure to store data in fields and columns.

Field

A column within a table, with an identifier and data type.

Record

An instance of an object with a database, (each row of the database).

Primary Key

A field which uniquely identifies each record in a table, each value in the field is unique.

Foreign Key

A field in one table which is the primary key of another, which links the two tables.

Data redundancy

Is when the same data exists in multiple places within a database.

Data Inconsistency

Is when the same data exists in multiple places within a database but the instances of the data are not identical.

SQL

Structured Query Language - Used to query, create, search and maintain a database.

Select

Returns a subset of the data based on given criteria.

Update

Updates values in the database.

Insert

Inserts a new record into the database.

Delete

Removes data from the database based on criteria.