MATSEC SEC Information Technology key terms

The physical components of a computer system that you can touch, such as the processor, memory chips, circuit boards, keyboard, monitor and printer. It is distinct from the programs and data that run on it.

The set of programs, instructions and data that tell computer hardware what to do. It includes operating systems, application programs and utilities, and has no physical form of its own.

The main chip that fetches, decodes and executes instructions, performing arithmetic, logic and control operations. Its speed is often measured in gigahertz, and it coordinates the rest of the computer's components.

Volatile main memory that holds programs and data currently in use so the processor can reach them quickly. Its contents are lost when power is switched off, so work must be saved to backing storage.

Non-volatile memory whose contents are written during manufacture and normally cannot be changed by the user. It typically stores firmware such as the bootstrap program needed to start the computer.

A small, very fast block of memory placed close to the processor that stores frequently used instructions and data. It reduces the average time needed to access main memory and so speeds up processing.

A technique in which part of secondary storage is used as an extension of RAM, allowing programs larger than physical memory to run. Excessive use causes disk thrashing and slows the system noticeably.

Non-volatile storage such as a hard disk, solid-state drive, optical disc or USB flash drive, used to keep files and programs permanently. It is slower and cheaper per gigabyte than main memory.

Any hardware unit connected to and controlled by the computer, such as a keyboard, mouse, scanner, printer or speaker. Peripherals are classed as input, output or storage devices.

Hardware used to enter data or instructions into a computer system, for example a keyboard, mouse, touchscreen, scanner, microphone or barcode reader. Choosing the right one depends on the type and volume of data.

Hardware that presents processed data to the user in a readable or usable form, such as a monitor, printer, plotter or speaker. Some devices, like touchscreens, act as both input and output.

System software that manages hardware, memory, files and processes, and provides a user interface so applications can run. Examples include Windows, macOS, Linux, Android and iOS.

Programs written to help users carry out particular tasks, such as word processing, spreadsheets, databases, browsers or games. They rely on the operating system to access hardware resources.

A small piece of system software that performs maintenance or housekeeping tasks, such as antivirus scanning, disk defragmentation, file compression or backup. Utilities help keep a system secure, efficient and reliable.

A translator that converts an entire high-level language program into machine code before it is run, producing an executable file. Errors are reported after the whole program is analysed.

A translator that converts and executes a high-level program one statement at a time, stopping when it meets an error. It is useful for testing but generally runs more slowly than compiled code.

Program instructions written by a programmer in a high-level or assembly language, which must be translated before the processor can execute them. It is human-readable and can be edited and maintained.

The binary instructions that a processor can execute directly, made up of operation codes and operands. It is produced from source code by a compiler or assembler and is not easily read by humans.

A finite, ordered set of unambiguous steps that solves a problem or completes a task. Algorithms can be represented as pseudocode, flowcharts or program code before being implemented.

A structured, informal way of writing an algorithm using English-like statements and standard keywords such as IF, WHILE and ENDIF. It is not tied to any programming language and is easy to turn into code.

A diagram that represents an algorithm using standard symbols: ovals for start and end, parallelograms for input and output, rectangles for processes and diamonds for decisions, joined by arrows showing sequence.

A named location in memory whose stored value can change while a program runs. Each variable has a data type and an identifier, and must usually be declared before use.

A named value that is fixed when the program is written and cannot be changed during execution, such as a tax rate or the value of pi. It makes programs easier to read and maintain.

A classification that defines what kind of values a variable may hold and which operations are allowed, for example integer, real, character, string or Boolean. It also determines how much storage is needed.

A data type with only two possible values, true or false, used to store the result of a comparison or a flag. Boolean expressions control selection and iteration in programs.

A programming construct that chooses which statements to execute depending on whether a condition is true or false, using IF, THEN, ELSE or CASE. It gives a program the ability to make decisions.

A programming construct that repeats a block of statements, either a fixed number of times (FOR loop) or while a condition holds (WHILE or REPEAT loop). It avoids duplicating code.

An organised collection of related data stored so that it can be easily accessed, managed and updated, usually through a database management system. Data is arranged in tables, records and fields.

A single column in a database table that holds one attribute of the data, such as surname or date of birth. Every field has a defined data type and a name.

A complete row in a database table, made up of related fields describing one entity, such as one customer or one order. Records are added, edited, deleted and searched by users or programs.

A field, or combination of fields, chosen to uniquely identify each record in a table. It cannot contain duplicate values or be left empty, and it links tables together as a foreign key elsewhere.

A field in one table that holds the primary key value of a record in another table, creating a relationship between the two. It enforces referential integrity so records cannot point to missing data.

A standard language for creating, querying and updating relational databases. Statements such as SELECT, FROM, WHERE and ORDER BY retrieve data, while INSERT, UPDATE and DELETE change it.

A request for information from a database that specifies which fields, tables and conditions are involved. Queries can be written in SQL or built with a query-by-example grid in a database package.

Two or more computers connected together so they can share data, programs and hardware such as printers. Networks may be local (LAN) or wide (WAN) and require protocols and addressing to communicate.

A network covering a small geographical area such as a school, office or home, usually owned and managed by one organisation. Devices are connected by cable or Wi-Fi through switches and a router.

A network that spans a large geographical area, linking sites in different towns or countries, often using telecommunications links leased from a provider. The internet is the largest example of a WAN.

A set of agreed rules governing how devices exchange data over a network, covering message format, timing and error handling. Examples include TCP/IP for the internet, HTTP for web pages and SMTP for email.

A unique numerical label given to each device on a network so data can be routed to it, such as 192.168.1.10 (IPv4) or a longer IPv6 form. Addresses may be static or assigned dynamically by DHCP.

A network device that forwards data packets between different networks, choosing the best path and joining a home or school LAN to the internet. It uses IP addresses to decide where to send traffic.

The worldwide network of interconnected networks that communicates using the TCP/IP protocol suite. It supports services such as the World Wide Web, email, file transfer, streaming and voice over IP.

A service running on the internet in which documents and resources are identified by URLs, linked by hyperlinks and transferred using HTTP or HTTPS. It is accessed through a web browser.

The full address of a resource on the web, consisting of a protocol, domain name and path, such as https://example.com/page.html. The domain name is translated to an IP address by DNS.

Application software used to request, interpret and display web pages, for example Chrome, Firefox, Edge or Safari. It renders HTML, runs scripts and stores bookmarks, history and cookies.

The markup language used to structure web page content with tags such as headings, paragraphs, lists, links and images. It describes the meaning and layout of content, not its visual styling.

The process of scrambling data using a key so that it cannot be read by anyone who does not hold the key. It protects information in transit and at rest, and is reversed by decryption.

Hardware or software that monitors incoming and outgoing network traffic and blocks anything that does not match a set of security rules. It helps protect a network from unauthorised access.

Any software written to damage, disrupt or gain unauthorised access to a computer system, including viruses, worms, trojans, spyware and ransomware. Antivirus software and updated systems help defend against it.

A social-engineering attack in which a criminal sends a fake message, often by email, pretending to be a trusted organisation in order to trick the recipient into revealing passwords or bank details.

A copy of data or programs kept on separate storage so that it can be restored if the originals are lost, corrupted or damaged. Backups should be regular, verified and stored off-site.

A user interface built from windows, icons, menus and a pointer, allowing users to operate a computer with a mouse or touch rather than by typing commands. It is generally easier for beginners than a command line.

The process of reducing a file's size by encoding its data more efficiently, either losslessly (so the original is restored exactly) or lossily (as with some image, audio and video formats). It saves storage space and speeds up transfer.

The delivery of computing services such as storage, software and processing power over the internet, from remote servers, on demand. Users pay for what they use and can access data from any connected device.