Computer words explained in plain English. Dotted underlines in lessons link here.
515 of 515 terms shown
Keep three copies of your data, on two kinds of storage, with one copy kept somewhere else.
Example: Amina keeps her files on her laptop, a copy on an external drive at home and a third copy in cloud storage.
Related: Backup, Cloud storage
Learn more: Why backups matter and the ways data is lost, Making a backup plan and testing a restore
The complete address of a file or folder, starting from the very top of the file system.
Example: On Linux, /home/joseph/Documents/cv.odt is an absolute path; on Windows, C:\Users\Joseph\Documents\cv.docx.
Related: Relative path, File path
Learn more: Folder hierarchies and file paths
An absolute reference is a cell address with dollar signs that does not change when the formula is copied.
The dollar signs lock the column, the row or both. $F$1 always points at F1. It is used for a rate or a setting that many formulas share.
Example: =B2*$F$1 keeps using the rate in F1 when copied down.
Related: relative reference, Cell reference, Formula
Learn more: Formulas, functions and cell references
Hiding the complicated details of one layer so the layer above can use it simply.
Example: You save a file without knowing which part of the disk holds it, because the operating system hides that.
Related: Operating system, Application
Learn more: Hardware, operating system and applications as layers
The kind of access a person is given to something you share, such as only viewing it or being allowed to edit it.
Example: You share a budget with your sister as 'viewer', so she can read it but not change the numbers.
Related: Sharing link, Permission
Learn more: Sharing files: attachments, links and permissions
A device that gives wireless devices a place to join a wired network.
Example: An office puts an access point on the ceiling so laptops can use Wi-Fi in every room.
Related: Wi-Fi, Router, Network
Learn more: Routers, switches, modems, access points, Ethernet and Wi-Fi
Making devices, documents and websites usable by people with different abilities, such as poor sight, hearing or movement.
Example: Turning on larger text or adding captions to a video makes it easier for more people to use.
Related: Screen reader, Alt text, Colour contrast
Learn more: Accessibility, zoom and comfortable use
The steps a service offers to help you regain access when you cannot sign in.
Example: Joseph used a recovery code to get back into his email after losing his phone.
Related: Recovery code, Multifactor authentication (MFA)
Learn more: Multifactor authentication, recovery codes and sessions
The address bar is the box at the top of a browser where you type a web address or a search and where the current address is shown.
Most browsers use it for both addresses and searches. Reading the address in it is the best quick check of which site you are really on.
Example: Amina clicks the address bar, types a library name and presses Enter.
Related: URL, Browser, search engine
Learn more: How a web browser works for you
A user account allowed to change important settings and install software for the whole computer.
Example: Amina's laptop asks for the administrator password before it installs a new program.
Related: User account, Permission, sudo
Learn more: User accounts, permissions, updates and drivers
A scam that asks you to pay a fee first for a job, prize or loan that never arrives.
Example: Amina was asked for a registration fee for a job she never applied for.
Related: Scam
Learn more: Common scams: jobs, investments, impersonation and romance
Software that shows unwanted adverts, and sometimes tracks what you do.
Example: After installing a free tool, Amina's browser filled with pop-up adverts from adware.
Learn more: Threats, vulnerabilities, risks and malware
A setting that switches off all wireless radios, including Wi-Fi and Bluetooth, at once.
Example: A laptop shows no Wi-Fi networks because Airplane mode was switched on by a function key.
Related: Pairing
Learn more: No internet, printer failures, Bluetooth and sound problems
A step-by-step set of instructions for solving a problem or completing a task.
Example: A recipe for making tea is an algorithm: boil water, add leaves, wait, pour.
Related: Condition, Loop, Function
Learn more: Algorithms, sequencing, pseudocode and flowcharts
A short written description of a picture, read aloud for people who cannot see it.
Example: The alt text for a photo might be 'A girl holding a certificate on stage'.
Related: Accessibility, Screen reader
Learn more: Tables, images, checking, track changes and exporting to PDF
Software that scans for known harmful programs and tries to stop or remove them.
Example: Your antivirus warns you that a file you just downloaded contains a virus.
Related: Malware, Virus, Firewall
Learn more: Everyday defences: updates, antivirus, firewalls and least privilege
A set of rules that lets one program ask another program for information or actions.
Example: A weather app uses an API to ask a weather service for today's forecast.
Related: Application, Server, JavaScript
Learn more: JavaScript basics: variables, conditions, loops, functions, arrays and objects
The built-in Ubuntu store where you search for, install and remove apps.
Example: Open App Center, search for 'VLC' and press Install.
Related: Package manager, Snap package, Repository
Learn more: Installing and removing software on Ubuntu
Your decision about whether a program may use a sensitive feature such as the camera, microphone or your location.
Example: Allowing a video call program to use the camera but denying it to a game.
Related: Permission, Application
Learn more: Privacy permissions, notifications and application defaults
A catalogue run by the system maker where you find, install, update and remove apps in one place.
Example: The App Center on Ubuntu and the Microsoft Store on Windows.
Related: Application, Package manager
Learn more: Applications: installing, updating and removing
Software an employer uses to collect, sort and search job applications.
Example: A website that scans uploaded CVs for the skills listed in a job advert.
Learn more: Digital job applications
A program that lets you do a particular job, such as writing, browsing or editing photos.
Example: A word processor, a web browser and a calculator are all applications.
Related: Operating system, Software
Learn more: What happens when a computer starts
Ubuntu's typed-command tool for installing, updating and removing software from its official sources.
It does the same job as the App Center, but by command. You will use it in a later module, after permissions are taught.
Example: The App Center and apt both get software from Ubuntu's repositories.
Related: Package manager, Repository, sudo
Learn more: Applications: installing, updating and removing
A single file that holds other files and folders packed together.
Example: A .zip archive can hold forty photos so you can email them as one attachment.
Related: ZIP, Compression
Learn more: Files, folders, names and extensions
Extra information you give to a command so it knows what to work on.
Example: In 'ls Documents', the word Documents is the argument telling ls which folder to list.
Related: Command, Option (flag)
Learn more: Terminal, shell and your first commands
An ordered list of values kept together in one variable and numbered from zero.
Example: const seeds = ["bean", "maize", "kale"]; seeds[0] is "bean".
Related: Variable, Object (JavaScript)
Learn more: JavaScript basics: variables, conditions, loops, functions, arrays and objects
Computer systems that do tasks which normally need human thinking, such as recognising speech or writing text.
Example: A phone that turns your spoken words into typed text uses artificial intelligence.
Related: Machine learning, Large language model
Learn more: What AI is and how it learns
Anything you want to protect because it has value, such as data, a device or an account.
Example: Wanjiru's accounts spreadsheet is an asset because the shop cannot run without it.
Related: Threat model, Backup
Learn more: Threat modelling and secure configuration
An attachment is a file sent along with an email message.
Attachments are a common way to spread malware, so open only the ones you expected from people you know, and check the file type.
Example: Wanjiru attaches her CV as a PDF to an email to an employer.
Related: PDF, Malware, File extension
Learn more: Writing professional emails, attachments and etiquette
All the places where someone could try to get into a system, such as open services, accounts and ports.
Example: Turning off a service you never use removes one way in and shrinks the attack surface.
Learn more: Threat modelling and secure configuration
Proving that you are who you say you are, for example with a password and a code.
Example: Typing a password and then a code from your phone to sign in.
Related: Authorisation, Multifactor authentication (MFA)
Learn more: Authentication, network security and safe lab practice
An app on your phone that creates short-lived codes for signing in.
Example: Wanjiru reads a six-digit code from her authenticator app, which changes every thirty seconds.
Related: Multifactor authentication (MFA), Passkey
Learn more: Multifactor authentication, recovery codes and sessions
Setting things up so the computer does a repeated task for you with little or no manual effort.
Example: Copying one formula down 200 spreadsheet rows instead of typing each total.
Related: Batch processing, Shell script
Learn more: Automating repetitive tasks safely
How much of the time a service is working and reachable when you need it.
Example: A service with 99.9 per cent availability is down for under nine hours a year.
Related: Cloud computing, Backup
Learn more: Local vs cloud computing
A separate copy of your files kept so you can get them back if the originals are lost or damaged.
Example: Copying your photos to an external drive each Sunday is a backup.
Related: Cloud storage, Ransomware, Sync
Learn more: Why backups matter and the ways data is lost
The amount of data a connection can carry in a given time.
Example: A video call needs more bandwidth than sending a text message.
Related: Latency, Internet, Packet
Learn more: Packets, protocols, bandwidth and latency
Doing the same action to many items in one go, following one rule.
Example: Renaming a hundred photos with a single command.
Related: Automation, Dry run
Learn more: Automating repetitive tasks safely
An email field that sends a copy to people without showing their addresses to the other recipients.
Example: Sending a class notice to many parents with all addresses in Bcc, so nobody sees the others' addresses.
Related: Phishing, Netiquette
Learn more: Professional email, online meetings and etiquette
BCC is a box for recipients whose addresses are hidden from everyone else who gets the email.
It protects privacy when you write to many people who do not know each other. Do not use it to secretly involve someone in a private discussion.
Example: Amina invites twenty parents to a meeting and puts all their addresses in BCC.
Related: CC (carbon copy), email address
Learn more: Email basics: addresses, inbox, To, CC and BCC, Writing professional emails, attachments and etiquette
A repeated tendency of a system to favour or disadvantage certain people or views, usually because its training examples were unbalanced.
Example: A tool that assumes every doctor in a story is male because most of its examples did.
Related: Training data, Hallucination
Learn more: Hallucinations, bias, privacy and responsible use
A way of writing information using only two symbols, 0 and 1, matching a switch that is off or on.
Example: The number five is written 101 in binary.
Learn more: How computers process information
The smallest piece of information a computer stores: a single 0 or 1.
Example: One bit can say 'off' or 'on', like a light switch.
Learn more: How computers process information
A short-range wireless technology for connecting nearby devices such as headphones and keyboards.
Example: Pairing wireless earbuds with your phone uses Bluetooth.
Learn more: Ports, cables and peripherals
A bookmark is a saved shortcut to a web page so that you can return to it without searching again.
Example: Joseph bookmarks the page of his bus timetable and opens it from the bookmarks list each morning.
Related: Browser, URL, browser tab
Learn more: How a web browser works for you
A value that can only be true or false, used to answer yes or no questions in a program.
Example: The question 7 > 5 gives the boolean value true.
Learn more: Variables, data types, conditions, loops and functions
The process a computer goes through when it is switched on, ending with the operating system running.
Example: Booting takes a minute as the laptop checks its parts and loads the operating system.
Related: Firmware, Operating system, Login
Learn more: What happens when a computer starts
A small program that finds the operating system on the drive and starts loading it.
Example: On Ubuntu this is usually GRUB, and on Windows it is the Windows Boot Manager.
Related: Boot, UEFI, Operating system
Learn more: What happens when a computer starts
The idea that every element is a rectangle made of content, padding, border and margin.
Example: A card with 16px of padding and a 2px border, sitting 24px from its neighbours.
Learn more: The box model, Flexbox and Grid
A separate line of work in Git where you can try changes without disturbing the main version.
Example: A branch called new-colours for testing a different colour scheme.
Learn more: Project structure, code editors, local testing and Git
An application for visiting and viewing websites.
Example: Chrome, Firefox and Edge are browsers.
Related: URL, HTML, Web server
Learn more: How a web browser works for you
A small program inside your web browser that changes what the browser does.
Because it runs where you see your email and bank, a bad extension can read or change what you do online.
Example: An advert blocker that you add to your browser.
Related: Browser, Permission
Learn more: Default apps, file associations, licences and browser extensions
A browser tab is one web page open inside the browser window, shown as a small label along the top.
Example: Fatuma keeps her email in one tab and a recipe in another and clicks between them.
Related: Browser, address bar
Learn more: How a web browser works for you
Browsing history is the list of pages your browser remembers that you have visited.
It helps you find a page again. Anyone who can use your browser profile can read it, so it matters on shared computers.
Example: Kamau opens the history list to find a page he read yesterday.
Related: Browser, Cookie, private browsing
Learn more: History, cookies, cache, private browsing and permissions
Guessing passwords by trying huge numbers of possibilities automatically.
Example: A computer can try millions of short passwords a second, but far fewer long random ones.
Related: Passphrase, Data breach
Learn more: Passphrases, unique passwords and password managers
A mistake in a program that makes it behave in a way its maker did not intend.
Example: A calculator app that shows 2 + 2 = 5 has a bug.
Learn more: Errors and debugging
Extra programs packed together with the one you wanted, often installed unless you decline them.
Example: An installer that also changes your browser's home page unless you untick a box.
Learn more: Trusted sources, fake installers and bundled software
A group of eight bits, enough to store one letter or a small number.
Example: The letter 'A' is stored as one byte.
Learn more: How computers process information
A small store of recently used data kept close by so it can be fetched again quickly.
Example: Your browser keeps a site's logo in its cache so the page loads faster next time.
Learn more: History, cookies, cache, private browsing and permissions
A calendar is an app that stores your events, dates and reminders, and can share them with other people and devices.
Example: Joseph adds a clinic visit to his calendar and gets a reminder an hour before.
Related: calendar invitation, Sync, Time zone
Learn more: Shared documents, online meetings and calendars
A calendar invitation is a message that adds an event to your calendar when you accept it.
Example: Kamau accepts an invitation and the meeting appears in his calendar with a joining link.
Related: shared link, email address
Learn more: Shared documents, online meetings and calendars
When a system treats capital and small letters as different.
Example: On Linux, Notes.txt and notes.txt are two different files.
Related: File path, Command line
Learn more: Paths, case sensitivity, quoting, history and tab completion
CC is a box for people who should see an email for information and are not the main person you are writing to.
Everyone who receives the message can see who is in To and CC.
Example: Kamau writes to his manager and puts the team lead in CC.
Related: BCC (blind carbon copy), email address
Learn more: Email basics: addresses, inbox, To, CC and BCC, Writing professional emails, attachments and etiquette
A group of servers around the world that keep copies of a website so it loads quickly for everyone.
Example: A video site uses a CDN so a viewer in Nairobi gets the video from a nearby server.
Related: Hosting, Web server, Cache
Learn more: Web servers, hosting, CDNs, cookies and sessions
A cell is one box in a spreadsheet, where a row and a column cross.
Each cell has an address made from its column letter and row number. A cell can hold text, a number, a date or a formula.
Example: Cell B3 is in column B and row 3.
Related: Spreadsheet, Cell reference, Formula
Learn more: Spreadsheet basics: cells, rows, columns and data types
The name of a spreadsheet cell, made from its column letter and row number.
Example: B3 means column B, row 3.
Related: Spreadsheet, Formula
Learn more: Formulas, functions and cell references
A digital document that helps prove a website is really the one named in its address.
Example: Your browser checks the certificate of example.org before it shows the padlock.
Related: HTTPS, TLS (Transport Layer Security)
Learn more: Domains, URLs, HTTP and HTTPS
A qualification, usually from an exam, that shows you know a set of skills.
Example: CompTIA A+ is a certification for IT support skills.
Related: Portfolio
Learn more: Next steps: IT support, networking and Linux administration
An agreed table that says which number stands for which letter or symbol.
Unicode is the modern table. It covers letters from nearly every language, plus emoji.
Example: In the common encoding, the capital letter A is stored as the number 65.
Learn more: How computers process information
One full use of a battery's capacity, added up across several partial charges, which slowly wears the battery.
Example: Using half the battery on Monday and half again on Tuesday, with a charge in between, counts as about one cycle.
Related: Lithium-ion battery, Power supply
Learn more: Starting a laptop and logging in
A chart is a picture of numbers, such as columns, bars, lines or slices, that makes patterns easy to see.
Choose the type by the question: columns compare, lines show change over time and pies show parts of a whole. Give every chart a title, axis labels and honest axes.
Example: A column chart of each pupil's Maths mark.
Related: Spreadsheet, cell, Formula
Learn more: Charts and spreadsheet safety
A long string calculated from a file's contents that changes completely if even one part of the file changes.
Example: Comparing the checksum of your download with the one on the maker's official site.
Learn more: Trusted sources, fake installers and bundled software
A citation is a short note that tells the reader exactly where a quotation, fact or image came from.
Example: Wanjiru writes the author, title, publisher, date and web address of the page she used.
Related: plagiarism, primary source, copyright
Learn more: Copyright, plagiarism and citing sources
A device or program that asks another computer, called a server, for something.
Example: Your browser is a client when it asks a server for a web page.
Learn more: What is a network?
A hidden holding place where the computer keeps whatever you last copied or cut, until you paste it.
It normally holds one item at a time, so copying something new replaces the old item.
Example: Copy a sentence, switch to another document and paste it there.
Related: Keyboard shortcut
Learn more: The keyboard and essential shortcuts
How many tiny steps per second a processor's internal clock ticks, measured in gigahertz (GHz).
Clock speed alone does not tell you how fast a computer feels. The number of cores, the design of the processor and the memory and storage all matter too.
Example: A processor rated at 3 GHz ticks about three billion times each second.
Learn more: How computers process information, Inside the computer: CPU, RAM, motherboard and graphics
Using computers and services run by a company over the internet instead of on your own device.
Example: Writing a document in a web-based editor uses cloud computing.
Related: Cloud storage, Server, Internet
Learn more: Cloud storage, synchronisation and local vs cloud copies
A company that rents out computing power, storage and services over the internet.
Example: A small business rents a virtual server from a cloud provider instead of buying one.
Related: Cloud computing, Virtual machine
Learn more: Next steps: cybersecurity and cloud computing
Online space where a company keeps your files so you can reach them from any device.
Example: Saving photos to an online drive lets you open them on your phone and laptop.
Related: Backup, Sync, Cloud computing
Learn more: USB drives, external drives, safe ejection and formatting
A built-in command in PowerShell, named in a Verb-Noun style.
Example: Get-ChildItem is a cmdlet that lists the files in a folder.
Related: PowerShell, Command
Learn more: Command Prompt and PowerShell
A text editor made for writing code, with colouring, helpful hints and tools for working on many files.
Example: Visual Studio Code, or the plain Text Editor and Notepad for very small pages.
Learn more: Project structure, code editors, local testing and Git
The difference in brightness between text and its background, which affects how easy it is to read.
Example: Dark text on a white slide has good contrast; light grey text on white does not.
Related: Accessibility, Slide
Learn more: Presenting, accessibility, exporting and sharing
A typed instruction that tells the computer to do something.
Example: Typing 'pwd' tells a Linux terminal to show which folder you are in.
Related: Command line, Argument, Terminal
Learn more: Terminal, shell and your first commands
The list of commands you have typed earlier, which you can recall instead of retyping.
Example: Pressing the Up arrow in a terminal brings back your last command.
Related: Command line, Tab completion
Learn more: Paths, case sensitivity, quoting, history and tab completion
A way of controlling a computer by typing commands instead of clicking.
Example: Instead of clicking through folders, you type 'cd Documents'.
Related: Terminal, Shell, Command
Learn more: Terminal, shell and your first commands
The classic Windows program for typing commands.
Example: Type cmd in the Start menu to open Command Prompt.
Related: PowerShell, Command line, Windows Terminal
Learn more: Command Prompt and PowerShell
A saved snapshot of your project in Git, with a short message saying what changed.
Example: git commit -m "Add contact section"
Learn more: Project structure, code editors, local testing and Git
Software that lets programs made for one operating system try to run on another, though not always perfectly.
Example: Wine lets some Windows programs run on Ubuntu.
Related: Application, Operating system
Learn more: File systems and software compatibility
Making data take up less space by storing it more cleverly.
Example: Compressing a folder of documents shrinks it so it is quicker to send.
Related: ZIP, Lossless compression, Archive
Learn more: ZIP files: compressing and extracting
A machine that takes in information, works on it by following instructions, stores it and shows you the result.
Example: A laptop, a desktop, a tablet and a smartphone are all computers.
Learn more: What is a computer?
A test in a program that is either true or false and decides what happens next.
Example: 'If the password is correct, open the account' uses a condition.
Related: Loop, Variable, Algorithm
Learn more: Variables, data types, conditions, loops and functions
The developer tools panel where a page's messages and errors appear and where you can type JavaScript.
Example: console.log("hello") prints hello in the console.
Related: Developer tools, Error message
Learn more: Validation, error handling and browser developer tools
A small fan that moves air over hot parts and out of the computer.
Example: The whirring sound from the vents on a laptop that is working hard.
Related: Heatsink, Thermal throttling
Learn more: Power, cooling and the display
Copyright is the legal right of the creator of a work, such as a text, photo, song or program, to decide how it is copied and shared.
It arises automatically when a work is created. Rules and exceptions differ between countries, so this course gives general principles, not legal advice.
Example: A photographer owns the copyright in her photo, so you need her permission or a suitable licence to use it.
Related: Licence, Creative Commons, plagiarism
Learn more: Copyright, plagiarism and citing sources
One complete working unit inside a processor. More cores let it do several jobs at the same time.
Example: A quad-core processor has four cores, so it can run four streams of instructions at once.
Related: CPU, Clock speed
Learn more: Inside the computer: CPU, RAM, motherboard and graphics
The part of a computer that carries out instructions; its main thinking chip.
Example: A faster CPU lets a computer open programs and finish calculations more quickly.
Related: RAM, Motherboard, GPU
Learn more: How computers process information
When a program meets a problem it cannot handle and closes suddenly.
Example: A message saying a program 'closed unexpectedly' and its window vanishing.
Related: Frozen application
Learn more: Slow computers, frozen apps, full storage and crashes
Creative Commons is a family of free public licences that let creators say in advance how others may reuse their work.
Each licence has conditions, such as credit the author (BY), no commercial use (NC), no changes (ND) or share alike (SA). Read the conditions before reuse.
Example: A photo marked CC BY may be reused if you credit the photographer.
Related: copyright, Licence, citation
Learn more: Copyright, plagiarism and citing sources
The language that controls how a web page looks, such as colours, fonts and spacing.
Example: A CSS rule can make every heading on a page blue.
Related: HTML, JavaScript
Learn more: CSS basics: selectors, colours and typography
A CSS layout method that arranges items in rows and columns at the same time.
Example: grid-template-columns: 1fr 1fr 1fr makes three equal columns.
Learn more: The box model, Flexbox and Grid
The name of one thing CSS can change, written before a colon and its value.
Example: In color: darkgreen, color is the property.
Related: CSS, CSS selector
Learn more: CSS basics: selectors, colours and typography
The part of a CSS rule that says which elements the rule applies to.
Example: In h1 { color: green; }, the selector h1 picks every main heading.
Related: CSS, CSS property
Learn more: CSS basics: selectors, colours and typography
A plain-text file where each line is a row and commas separate the columns.
Example: A line such as `Amina,Nairobi,250` holds a name, a town and an amount.
Related: Dataset, Spreadsheet
Learn more: Next steps: programming, web development and data analysis
The arrow or mark on the screen that shows where you are pointing, or in text, where typing will appear.
Example: Move the mouse and the arrow moves; in a document the blinking line shows where the next letter will go.
Learn more: What happens when a computer starts
A short document listing your education, work and skills, used when applying for jobs.
Example: Salma sends her CV with a job application.
Related: Word processor, PDF
Learn more: Project: a CV, a formal letter and a report
An incident in which a company's stored information, such as passwords or emails, is stolen or exposed.
Example: A small shop's website had a data breach, and thousands of email addresses were leaked.
Related: Password manager, Personal data
Learn more: Passphrases, unique passwords and password managers
A company that collects personal information from many sources and sells it.
Example: A data broker built a profile of Joseph's interests from many sites and sold it to advertisers.
Related: Personal data, Tracking
Learn more: Personal information and your digital footprint
A building full of servers, with strong power, cooling and network links.
Example: A shop's website may run on a server in a data centre in another country.
Related: Server, Hosting, Cloud computing
Learn more: Web servers, hosting, CDNs, cookies and sessions
Sharing only the information that is truly needed.
Example: Wanjiru left optional boxes blank when signing up for a newsletter.
Related: Personal data, Privacy policy
Learn more: Personal information and your digital footprint
A data type is the kind of thing a cell holds, such as text, a number or a date.
The type decides what you can do with the data. Numbers can be added, but text cannot. A number stored as text is a common cause of wrong totals.
Example: The number 350 is a number, the word Rent is text, and 3 Apr 2026 is a date.
Related: cell, number format, Spreadsheet
Learn more: Spreadsheet basics: cells, rows, columns and data types
Data validation sets rules for what can be typed into a cell, such as a list of allowed values.
A drop-down list stops spelling variations, and number rules can refuse negative amounts. The rule guards typing but not pasting.
Example: A Category cell that accepts only Paper, Tools or Writing.
Related: sorting, filtering, Spreadsheet
Learn more: Sorting, filtering and data validation
A collection of related data, usually arranged as rows and columns.
Example: A spreadsheet with one row for every sale in a month is a dataset.
Related: Spreadsheet, CSV file
Learn more: Next steps: programming, web development and data analysis
An installable software file used by Ubuntu and other Debian-based Linux systems.
Example: Downloading chrome.deb and opening it installs Chrome on Ubuntu.
Related: Package manager, Dependency
Learn more: Installing and removing software on Ubuntu
Finding and fixing mistakes in a program.
Example: Debugging a game might mean working out why the score never goes up.
Related: Bug, Troubleshooting
Learn more: Errors and debugging
A fake photo, video or voice recording made with AI that looks or sounds like a real person.
Example: A made-up audio clip that copies someone's voice to ask for money.
Related: Generative AI, Scam
Learn more: Hallucinations, bias, privacy and responsible use
The program the computer uses automatically to open a certain kind of file or link.
Example: Making a PDF viewer the default for files that end in .pdf.
Related: File extension, Application
Learn more: Privacy permissions, notifications and application defaults
The device on a network, usually the router, that sends traffic on to other networks.
Example: Your laptop sends a request for a website to the default gateway at 192.168.1.1.
Related: Router, IP address, DHCP
Learn more: Files, processes and network diagnostics on Windows
Using several layers of protection so that if one fails, the others still help.
Example: A strong password, two-step sign-in and a recent backup protect an account in three different ways.
Related: Multifactor authentication (MFA), Backup
Learn more: Threat modelling and secure configuration
A finished item you have been asked to hand over, such as a report or a spreadsheet.
Example: In the electricity project the deliverables are a report, a spreadsheet, five slides and an email.
Related: Project brief, Naming convention
Learn more: Project, part 2: report, spreadsheet, presentation, email and backup
Another piece of software that a program needs in order to work.
Example: A video editor may depend on a codec package, which the installer fetches too.
Related: Package manager, Deb package
Learn more: Installing and removing software on Ubuntu
Putting your finished site on a server so other people can reach it on the internet.
Example: Uploading your folder to a static host and receiving a public web address.
Related: Static site, Hosting
Learn more: Final project: build and publish a personal web page
The part of an operating system that gives you the screen, windows, menus and icons you click.
Example: Ubuntu's default desktop environment is GNOME.
Related: Operating system, Taskbar, Dock
Learn more: What happens when a computer starts
A set of panels built into the browser for inspecting a page, running code and seeing errors and network requests.
Example: Pressing F12 in Firefox or Chrome opens the developer tools.
Learn more: Validation, error handling and browser developer tools
A Windows tool that lists the hardware in your computer and its drivers.
Example: Open Device Manager to see whether a printer has a driver problem.
Related: Driver, Windows Settings
Learn more: Task Manager, Device Manager, power, printers and Bluetooth
A service that automatically gives each device on a network an address.
Example: When your phone joins home Wi-Fi, DHCP hands it an address like 192.168.1.23.
Related: IP address, Router, Default gateway
Learn more: DHCP, DNS and the default gateway
The time for which a device may keep the address that DHCP gave it.
Example: A phone's lease lasts 24 hours and is renewed automatically while it stays connected.
Related: DHCP, IP address
Learn more: DHCP, DNS and the default gateway
A digital certificate is an electronic identity card that shows a website controls its domain name.
Browsers check it when a site uses HTTPS. A valid certificate shows the connection goes to that domain; it does not prove the site's owner is honest.
Example: A padlock beside the address means the browser accepted the site's certificate.
Related: HTTPS, TLS (Transport Layer Security), Domain name
Learn more: HTTPS and spotting suspicious websites
The trail of information about you that exists online, from what you post and what others post or collect.
Example: Amina searched her own name and found an old photo, a club list and a shop review.
Related: Personal data, Tracking
Learn more: Personal information and your digital footprint
A mark on a file, made with a secret key, that shows who published it and that it has not been changed since.
Example: Windows showing Verified publisher with a company name when you open a signed installer.
Related: Installer, Encryption
Learn more: Trusted sources, fake installers and bundled software
Another word for a folder: a container that holds files and other folders.
Example: On Linux, the Documents directory holds your documents.
Learn more: Files, folders, names and extensions
How much of a storage device is already filled with data and how much space is left.
Example: `df -h` shows that the main disk is 78% used.
Learn more: Services, logs, storage and backups for administrators
The flat screen itself, made of a grid of pixels that light up with colour.
Example: An LCD or OLED screen on a laptop or phone.
Related: Pixel, Resolution, Refresh rate
Learn more: Power, cooling and the display
A setting that draws text, icons and buttons larger without lowering the sharpness of the screen.
Example: Setting scaling to 150% on a high-resolution laptop so the writing is easy to read.
Related: Resolution, Pixel
Learn more: Display scaling, language, keyboard layout, date and time
The internet's phone book, which turns website names into the numeric addresses computers use.
Example: DNS turns example.com into an address like 93.184.216.34.
Related: Domain name, IP address, URL
Learn more: How a web browser works for you
A short-term memory of recent DNS answers, which saves asking the same question again.
Example: The second visit to a site is quicker to start because its address is already in the cache.
Related: DNS, Cache, DNS resolver
Learn more: DHCP, DNS and the default gateway
The server that looks up a name for you and returns its IP address.
Example: Your router passes the question about example.org to the resolver your provider runs.
Related: DNS, DNS cache, Domain name
Learn more: DHCP, DNS and the default gateway
The bar of app icons along the side or bottom of the Ubuntu screen.
Example: Click the Files icon on the Ubuntu dock to open your folders.
Related: Desktop environment, Workspace
Learn more: A tour of the Ubuntu desktop
The official written explanation of how a product, command or tool works.
Example: The Ubuntu help pages, or Microsoft's pages about Windows settings.
Related: Man page, Release notes
Learn more: Reading documentation and searching for error messages
The file type Microsoft Word uses for documents.
Example: report.docx opens in Word and in LibreOffice Writer.
Related: Word processor, Open Document Format, File extension
Learn more: Writing your first document in LibreOffice Writer
The browser's live, tree-shaped model of a web page, which JavaScript can read and change.
Example: Changing the text of a heading through the DOM updates what is on screen at once.
Related: JavaScript, HTML tag
Learn more: The DOM and events
The readable name of a website, such as example.com.
Example: In https://www.example.com/shop, example.com is the domain name.
Learn more: Trusted sources, fake installers and bundled software
A third-party website that collects links to many programs and earns money from adverts, rather than being run by the maker.
Example: A site listing free PDF viewers with several large Download buttons that are really adverts.
Related: Bundled software, URL
Learn more: Trusted sources, fake installers and bundled software
Software that lets the operating system talk to a piece of hardware.
Example: A printer will not print until the right driver is installed.
Related: Operating system, Driver update, Device Manager
Learn more: What happens when a computer starts
A newer version of a driver that fixes faults or improves how a device works.
Example: Updating the Wi-Fi driver fixed a laptop that kept dropping its connection.
Learn more: User accounts, permissions, updates and drivers
Running a task in a way that only shows what it would do, without changing anything.
Example: A rename script that prints the planned new names before it renames any file.
Related: Shell script, Automation
Learn more: Automating repetitive tasks safely, Your first simple shell scripts
Printing on both sides of a sheet of paper.
Example: Choosing duplex printing turns a ten-page document into five sheets.
Related: Print preview, Page range
Learn more: PDFs, print preview and printing
An email address is the unique name of a mailbox, written as a user name, an @ sign and a domain name.
Example: In amina.wanjiru@example.com, amina.wanjiru is the mailbox and example.com is the domain.
Related: Domain name, inbox, webmail
Learn more: Email basics: addresses, inbox, To, CC and BCC
An email signature is a short block of text, such as your name and contact details, added automatically at the bottom of your messages.
Example: Joseph's signature has his full name and his work telephone number.
Related: email address, inbox
Learn more: Email basics: addresses, inbox, To, CC and BCC
Scrambling data so only someone with the right key can read it.
Example: Encryption stops someone who intercepts your online banking from reading your details.
Related: HTTPS, TLS (Transport Layer Security), VPN (virtual private network)
Learn more: HTTPS and spotting suspicious websites
A named setting stored by the system that programs can look up.
Example: The HOME variable tells programs where your home folder is.
Related: PATH variable, Variable, Shell
Learn more: The filesystem hierarchy, environment variables and shell scripts
Arranging your seat, screen and keyboard so that using a computer does not strain your body.
Example: Raising the screen so the top is at about eye level and resting your feet flat on the floor.
Related: Accessibility
Learn more: Accessibility, zoom and comfortable use
A message from the computer or program that says something went wrong and often where and why.
Example: The browser console says: Uncaught SyntaxError: Unexpected token.
Related: Syntax error, Debugging
Learn more: Errors and debugging
A wired way to connect a device to a network using a cable.
Example: Plugging an Ethernet cable from a laptop into the router gives a steady connection.
Learn more: Ports, cables and peripherals
A function that the browser runs when something happens on the page, such as a click.
Example: A listener that shows a message when the Save button is clicked.
Learn more: The DOM and events
A fake Wi-Fi network that copies the name of a real one to catch your traffic.
Example: A hotspot called CafeFreeWiFi appeared next to the real CafeWiFi, but it was an evil twin.
Related: Wi-Fi, VPN (virtual private network)
Learn more: App permissions, public Wi-Fi and shared devices
An error that happens while a program is running and stops it unless the code handles it.
Example: Reading a property of undefined throws a TypeError exception.
Related: try/catch, Error message
Learn more: Validation, error handling and browser developer tools
The right to run a file as a program or script, or to enter a folder; shown as x.
Example: chmod u+x hello.sh lets the owner run hello.sh.
Related: Permission string
Learn more: Permissions, getting help, sudo and packages
A simple file system that Windows, Ubuntu, macOS and many cameras can all read and write, with no small file size limit.
Example: A 128 GB USB stick formatted as exFAT works on both a Windows laptop and an Ubuntu laptop.
Related: FAT32, File system, NTFS
Learn more: File systems and software compatibility
The standard file system that Ubuntu and many other Linux systems use on their main drive.
Example: Ubuntu's own drive is normally formatted as ext4.
Related: File system, NTFS
Learn more: File systems and software compatibility
An old, very widely understood file system that cannot hold a single file larger than 4 GB.
Example: A film file of 5 GB will not copy to a USB stick formatted as FAT32.
Related: exFAT, File system
Learn more: File systems and software compatibility
A named chunk of stored data, such as a document, photo or song.
Example: holiday.jpg is a file holding a photograph.
Related: Folder, File extension, File system
Learn more: What happens when a computer starts
The computer's list that says which app opens each type of file, according to its extension.
Example: Files ending in .pdf are associated with a document viewer.
Related: File extension, Default application
Learn more: Default apps, file associations, licences and browser extensions
The Windows program for browsing files and folders.
Example: Open File Explorer and click Downloads to see what you have saved.
Related: Folder, File path, Windows Settings
Learn more: File Explorer and Windows Settings
The letters after the last dot in a file name that show its type.
Example: In letter.docx, the extension .docx shows it is a Word document.
Learn more: Default apps, file associations, licences and browser extensions
A Windows feature that saves versions of the files in your user folders to an external drive or network location.
It is separate from the OneDrive folder backup, which keeps chosen folders in Microsoft's cloud.
Example: Kamau turned on File History with a USB hard disk and later opened an older version of his budget file.
Related: Backup, Version history, Restore
Learn more: Making a backup plan and testing a restore
The written route to a file through the folders that contain it.
Example: C:\Users\Joseph\Pictures\cat.jpg is the path to a picture.
Related: Absolute path, Relative path, Folder
Learn more: File Explorer and Windows Settings
The way a drive organises and keeps track of files and folders.
Example: A USB stick formatted as exFAT works on both Windows and Mac.
Related: Storage, Folder, File
Learn more: File systems and software compatibility
The standard layout of folders on a Linux system, all branching from one root.
Example: On Linux, /home holds users' files and /etc holds settings.
Related: Root, Directory, Absolute path
Learn more: The filesystem hierarchy, environment variables and shell scripts
Filtering hides the rows of a list that do not match your condition.
The hidden rows are not deleted. Clearing the filter brings them back. Gaps in the row numbers show that a filter is on.
Example: Filtering a stock list to show only the Writing category.
Related: sorting, Spreadsheet, data validation
Learn more: Sorting, filtering and data validation
A security feature that blocks unwanted network connections to or from your computer.
Example: The firewall stops an unknown program from receiving connections from the internet.
Related: Malware, Network, Antivirus
Learn more: Microsoft Store, Windows Update and Windows Security
Small built-in software stored on a hardware device that starts and controls it.
Example: The firmware on a motherboard starts the computer before the operating system loads.
Related: Boot, Motherboard, Driver
Learn more: What happens when a computer starts
A type of storage chip that keeps data without power and has no moving parts.
Example: It is used inside SSDs, USB sticks, memory cards and phones.
Related: SSD (solid-state drive), Storage
Learn more: Storage devices: SSD, hard disk, USB drives and memory cards
A CSS layout method that arranges items along one line, a row or a column.
Example: display: flex on a menu puts its links side by side.
Learn more: The box model, Flexbox and Grid
A diagram that shows the steps of an algorithm as boxes joined by arrows, with branches for yes or no questions.
Example: A chart that asks Is it raining? and points to Take an umbrella or Leave it at home.
Related: Algorithm, Pseudocode
Learn more: Algorithms, sequencing, pseudocode and flowcharts
A container for organising files and other folders.
Example: You might keep a folder called School with a folder for each subject inside.
Related: File, Directory, File path
Learn more: Ubuntu Files and your Home folder
The style of lettering used for text, such as Arial or Times New Roman.
Example: Choosing a clear font makes a CV easier to read.
Related: Paragraph style, Word processor
Learn more: Writing your first document in LibreOffice Writer
Making the operating system stop a program immediately, without letting it save or tidy up.
Anything you had not saved in that program is usually lost.
Example: Choosing End task in Windows Task Manager for a program that will not close.
Related: Frozen program, Process
Learn more: Sleep, restart, shut down and frozen computers
The visible caption of a form field, linked to the field so that screen readers and clicks connect the two.
Example: A label reading Email address linked to the email box.
Related: Semantic HTML, HTML attribute
Learn more: Tables, forms, semantic structure and accessibility
Preparing a drive with a file system, which erases everything that was on it.
Example: Formatting a USB stick as exFAT so it works on both Windows and Ubuntu.
Related: File system, Backup
Learn more: File systems and software compatibility
An instruction in a spreadsheet cell that calculates a value from other cells.
Example: =B2+B3 adds the numbers in cells B2 and B3.
Related: Cell reference, Spreadsheet, Function
Learn more: Formulas, functions and cell references
The part of a drive's capacity that is still empty and ready for new files.
Example: A drive with 20 GB of free space can still store about 5,000 photos.
Learn more: Bytes, capacity, free space and the difference between RAM and storage
A model where the basic app is free and extra features cost money.
Example: A photo app that is free but charges to export high-quality files.
Related: Subscription, Licence
Learn more: Default apps, file associations, licences and browser extensions
A program that has stopped answering your clicks while the rest of the computer may still work.
Example: A document editor that goes pale and shows '(Not Responding)' while you try to open a huge file.
Related: Crash, Task Manager
Learn more: Slow computers, frozen apps, full storage and crashes
A program that has stopped reacting to clicks and keys, although the rest of the computer may still work.
Example: A word processor window turns pale and says it is not responding.
Related: Force quit, Process
Learn more: Sleep, restart, shut down and frozen computers
A named block of instructions in a program that you can reuse whenever needed.
Example: A function called greet can be used each time you want to say hello.
Related: Variable, Algorithm, Loop
Learn more: Variables, data types, conditions, loops and functions
A spreadsheet function is a ready-made formula with a name, such as SUM or AVERAGE.
You write the name, then the input in brackets. The input is often a range, such as B2:B6, meaning all cells from B2 to B6.
Example: =SUM(B2:B6) adds the five numbers in cells B2 to B6.
Related: Formula, Cell reference, Spreadsheet
Learn more: Formulas, functions and cell references
AI that creates new text, images, sound or code instead of only labelling or sorting things.
Example: A chatbot that writes a first draft of an email from a short request.
Related: Large language model, Prompt (AI)
Learn more: What AI is and how it learns
A movement of one or more fingers on a touchpad or touchscreen that tells the computer to do something.
Example: Sliding two fingers up or down on the touchpad scrolls a page.
Learn more: Mouse and touchpad skills
A unit of data size equal to about one billion bytes.
Example: A phone with 64 GB of storage can hold many apps and photos.
Learn more: How computers process information
A tool that records the history of changes to your project files so you can go back to earlier versions.
Example: Before trying a risky change, you save a Git snapshot so you can undo it.
Related: Repository, Backup
Learn more: Project structure, code editors, local testing and Git
A website that stores Git repositories online so they are backed up, shareable and can be published.
Example: Uploading your personal page project to a GitHub repository.
Related: Git, Repository
Learn more: Project structure, code editors, local testing and Git
The desktop environment Ubuntu uses by default: the panels, dock, menus and windows you see and click.
Example: The Activities button and the dock on Ubuntu are part of GNOME.
Related: Desktop environment, Operating system
Learn more: What an operating system does
A chip that specialises in drawing images and video on the screen.
Example: A GPU helps a game draw smooth moving pictures.
Related: CPU, Motherboard
Learn more: Inside the computer: CPU, RAM, motherboard and graphics
A command that searches inside text files for lines that match a word or pattern.
Example: grep milk shopping.txt prints every line containing 'milk'.
Learn more: Reading and searching: file, cat, less, head, tail, grep and find
A named set of user accounts that can share permissions on files and tasks.
Example: Amina belongs to the group sudo, which allows administrator actions.
Related: Permission string
Learn more: Looking at the system: df, du, free, ps, top, whoami and id, Permissions, getting help, sudo and packages
When an AI tool states something false as if it were true.
Example: A chatbot invents a book title that does not exist.
Related: Large language model, Artificial intelligence
Learn more: Evaluating sources and spotting misinformation
A storage device that keeps data on spinning magnetic disks.
Example: An older desktop may store its files on a hard disk that you can sometimes hear whirring.
Related: SSD (solid-state drive), Storage
Learn more: Storage devices: SSD, hard disk, USB drives and memory cards
The physical parts of a computer that you can touch.
Example: The screen, keyboard, battery and the chips inside.
Learn more: What is a computer?
A common connection that carries picture and sound to a monitor or television.
Example: A cable from a laptop's HDMI port to a TV so you can show a film on the big screen.
Related: Port, Output device
Learn more: Ports, cables and peripherals
A block of metal fins fixed to a hot chip to draw heat away from it so air can carry it off.
Example: The metal fins under the fan on top of a desktop processor.
Related: Cooling fan, Thermal throttling
Learn more: Power, cooling and the display, Inside the computer: CPU, RAM, motherboard and graphics
The team that people contact first when their technology does not work.
Example: Fatuma messages the school help desk because she cannot sign in.
Related: Ticket, Troubleshooting
Learn more: Next steps: IT support, networking and Linux administration
A power state that saves your open work to storage and switches the computer fully off.
Example: After hibernation, your laptop starts again with your documents still open.
Related: Sleep mode, Boot
Learn more: What happens when a computer starts
A display setting that uses strongly different colours, such as light text on a dark background, to make things easier to see.
Example: Turning on high contrast so window edges and buttons stand out clearly.
Related: Screen magnifier, Accessibility
Learn more: Accessibility, zoom and comfortable use
Your own personal folder on Linux, where your documents and settings live; written ~ in commands.
Example: /home/amina is Amina's home directory, and cd ~ takes her back to it.
Related: Working directory
Learn more: Finding your way: pwd, ls and cd
Your personal folder on Linux, where your own files and settings are kept.
Example: On Ubuntu, Amina's home folder is /home/amina.
Related: Folder, User account
Learn more: Ubuntu Files and your Home folder
One step of a packet's journey from one router to the next.
Example: A packet from Amina's laptop to a website may pass through twelve hops.
Related: Packet, Router, Traceroute
Learn more: Packets, protocols, bandwidth and latency
A service that keeps a website's files on a server so people can visit it.
Example: You pay a hosting company to keep your website online.
Related: Web server, CDN, Domain name
Learn more: Web servers, hosting, CDNs, cookies and sessions
The language that describes the content and structure of a web page.
Example: <h1>Welcome</h1> in HTML marks a main heading.
Related: CSS, JavaScript, Browser
Learn more: How a web browser works for you
Extra information placed inside an opening tag as a name and a value.
Example: In <a href="about.html">, href is the attribute and about.html is its value.
Learn more: HTML structure: elements, tags, attributes, headings, links and images
A word inside angle brackets that marks the start or end of an HTML element.
Example: The tags <p> and </p> open and close a paragraph.
Related: HTML, HTML attribute
Learn more: HTML structure: elements, tags, attributes, headings, links and images
The set of rules browsers and web servers use to exchange web pages.
Example: Your browser sends an HTTP request and the server sends back the page.
Related: HTTPS, Protocol, Web server
Learn more: Packets, protocols, bandwidth and latency
The message a browser sends to a web server asking for a page or file.
Example: GET /home asks the server for the page called home.
Related: HTTP, HTTP status code
Learn more: Domains, URLs, HTTP and HTTPS
A three-digit number in a server's reply that says whether the request worked.
Example: 200 means success, 404 means the page was not found, and 500 means the server had a problem.
Related: HTTP, HTTP request
Learn more: Domains, URLs, HTTP and HTTPS
The secure version of HTTP, which encrypts what passes between you and a website.
Example: A padlock and https:// in the address bar show the connection is encrypted.
Related: HTTP, TLS (Transport Layer Security), Encryption
Learn more: Display scaling, language, keyboard layout, date and time
Text or an image on a web page that takes you to another page or file when you select it.
Example: The words Read the seed guide, which open another page when clicked.
Learn more: HTML structure: elements, tags, attributes, headings, links and images
A sensible guess about the cause of a problem, which you then test.
Example: 'The printer is offline because the Wi-Fi dropped' is a hypothesis you can check.
Related: Troubleshooting, Debugging
Learn more: The eight-step troubleshooting method
A service where you rent raw computing power, storage and networking and set up the software yourself.
Example: Renting a virtual server and installing your own system on it.
Learn more: Web applications and service models
A small picture on the screen that stands for an app, file or folder.
Example: The yellow folder picture that stands for a folder.
Learn more: What happens when a computer starts
Using someone else's personal details to pretend to be them, often to get money or credit.
Example: A criminal used a leaked name and ID number to apply for a loan.
Related: Personal data, Phishing
Learn more: Personal information and your digital footprint
The inbox is the folder where new email messages arrive.
Example: Joseph's inbox shows unread messages in bold at the top.
Related: email address, spam, webmail
Learn more: Email basics: addresses, inbox, To, CC and BCC
The planned steps you follow when something goes wrong with security, from spotting it to recovering.
Example: After a lost laptop, you change passwords, tell the owner and check the backups.
Related: Threat model, Backup
Learn more: Next steps: cybersecurity and cloud computing
A backup that, after the first full copy, saves only the files that have changed since the last run.
Example: The first backup of Wanjiru's laptop took two hours, but each nightly incremental backup takes a few minutes.
Learn more: Making a backup plan and testing a restore
A device you use to give information to a computer.
Example: Keyboard, mouse, touchpad, microphone, webcam.
Related: Output device
Learn more: What is a computer?
A small program or package whose job is to put an application's files in the right places and register it with the computer.
Example: Double-clicking a file ending in .exe on Windows starts an installer.
Related: Application, Package manager
Learn more: Applications: installing, updating and removing
One small, exact step that a processor can carry out, such as adding two numbers.
Example: Add the number in box A to the number in box B.
Learn more: How computers process information
Unwanted signals or obstacles that weaken or disturb a radio connection.
Example: Thick walls and busy neighbouring networks can interfere with a Wi-Fi signal.
Related: Wi-Fi, Signal strength
Learn more: Wi-Fi signal, router restarts and firewalls: diagnosing step by step
The worldwide network of connected networks that lets computers share information.
Example: Sending an email to a friend in another country uses the internet.
Related: Network, Internet service provider (ISP), WAN (wide area network)
Learn more: Display scaling, language, keyboard layout, date and time
A company you pay to connect your home or office to the internet.
Example: Joseph's provider brings a fibre line into his house and sends a bill each month.
Related: Internet, Modem, WAN (wide area network)
Learn more: What is a network?
A number that identifies a device on a network so data can find it.
Example: A home laptop might have the address 192.168.1.23.
Learn more: How a web browser works for you
The older and still most common kind of IP address, written as four numbers separated by dots.
Example: 192.168.1.20 is an IPv4 address.
Related: IP address, IPv6, Octet
Learn more: IP addresses: IPv4, IPv6, public and private
The newer kind of IP address, much longer than the old kind, so there are enough for every device.
Example: An IPv6 address looks like 2001:db8::1.
Related: IP address, DNS
Learn more: IP addresses: IPv4, IPv6, public and private
A programming language that makes web pages respond and change as you use them.
Example: JavaScript shows a message when you press a button on a page.
Learn more: JavaScript basics: variables, conditions, loops, functions, arrays and objects
A plain-text way of writing data as named values and lists, used by programs to store and exchange information.
Example: { "name": "Amina", "seeds": 12 }
Related: Object (JavaScript), Array
Learn more: Validation, error handling and browser developer tools
The core part of an operating system that manages the hardware and runs everything else.
Example: The kernel decides which program gets to use the CPU next.
Related: Operating system, Driver, Process
Learn more: What happens when a computer starts
The setting that decides which character each key produces, such as QWERTY for English.
Example: If the @ symbol appears when you press the double-quote key, the layout is set to a different region.
Related: Input device
Learn more: The keyboard and essential shortcuts
A combination of keys, pressed together, that does a job faster than using the mouse and menus.
Example: Ctrl and C together copy the selected text.
Related: Modifier key, Clipboard
Learn more: The keyboard and essential shortcuts
Spyware that secretly records what you type, so that passwords can be stolen.
Example: A keylogger hidden in a fake download sent Joseph's typing to a criminal.
Learn more: Threats, vulnerabilities, risks and malware
A network covering a small area such as a home or school.
Example: The devices in your house sharing one router form a LAN.
Related: WAN (wide area network), Router, Network
Learn more: What is a network?
An AI system trained on huge amounts of text so it can read and write language.
Example: A chatbot that drafts an email for you is built on a large language model.
Related: Artificial intelligence, Machine learning, Hallucination
Learn more: What AI is and how it learns
The time it takes for data to travel from one place to another and back.
Example: High latency makes a video call lag so people talk over each other.
Learn more: Packets, protocols, bandwidth and latency
Lateral reading means leaving a page to see what other trustworthy sources say about it and about who runs it.
Professional fact-checkers do this first. Staying on a page and judging it by how professional it looks is easy to fool.
Example: Before trusting an unfamiliar health site, Fatuma opens a new tab and searches for the organisation's name.
Related: misinformation, primary source, browser tab
Learn more: Evaluating sources and spotting misinformation
Giving a person or programme only the access it needs, and no more.
Example: Joseph uses a standard account for daily work, so a bad download cannot change the whole system.
Related: User account, Administrator, Permission
Learn more: Everyday defences: updates, antivirus, firewalls and least privilege
A free set of office programs for documents, spreadsheets and presentations.
Example: LibreOffice Writer is the word processor in the set.
Related: Word processor, Open source, Spreadsheet
Learn more: Writing your first document in LibreOffice Writer
The rules that say how you are allowed to use a piece of software or content.
Example: A licence may allow you to install a program on only one computer.
Related: Open source, Application
Learn more: Default apps, file associations, licences and browser extensions
The amount of vertical space between lines of text.
Example: Double line spacing leaves room for comments on a printed draft.
Related: Paragraph style, Margin
Learn more: Headings, margins, lists, headers, footers and page numbers
The rechargeable battery type used in nearly all laptops and phones.
It stores a lot of energy in a small space. If it is damaged, swollen or overheated it can be a fire risk.
Example: The flat battery pack under a laptop's keyboard.
Related: Power supply
Learn more: Power, cooling and the display, Hardware faults and what not to repair yourself
A local copy is a file stored on your own device, as opposed to one that exists only online.
Example: Amina's essay is stored on her laptop as a local copy and also in her cloud storage.
Related: Cloud storage, Sync, offline access
Learn more: Cloud storage, synchronisation and local vs cloud copies
The setting that lets apps and websites learn where your device is.
Example: Amina allowed a maps app to use her location only while the app is open.
Related: Permission, Digital footprint
Learn more: App permissions, public Wi-Fi and shared devices
A screen that hides your work and asks for your password, while your programs keep running behind it.
Locking is different from logging out: logging out closes your programs, locking does not.
Example: Press the Super key and L on Ubuntu, or the Windows key and L on Windows, before you walk away.
Related: Login, User account
Learn more: Starting a laptop and logging in
A record that a system or program writes, line by line, about what happened and when.
Example: A log line may say that a sign-in failed at 09:14 for the user joseph.
Learn more: Services, logs, storage and backups for administrators
A mistake where the code runs without complaint but does the wrong thing.
Example: A discount that is added to the price instead of taken off.
Related: Syntax error, Debugging
Learn more: Errors and debugging
Proving who you are, usually with a password, to start using a computer or account.
Example: You enter your password at the login screen to reach the desktop.
Related: User account, Password manager
Learn more: What happens when a computer starts
A look-alike domain is an address made to resemble a real one, using a swapped letter, an extra word or a long subdomain.
Criminals use it in phishing and fake shops. Read the address from the right, before the first single slash, to find who controls it.
Example: safarisavlngs.example looks like safarisavings.example but is a different domain.
Related: Phishing, Domain name, HTTPS
Learn more: HTTPS and spotting suspicious websites
A part of a program that repeats instructions again and again.
Example: A loop prints the numbers 1 to 10 without writing ten separate lines.
Related: Condition, Function, Algorithm
Learn more: Variables, data types, conditions, loops and functions
Making a file smaller in a way that lets you get back the exact original.
Example: Unzipping a ZIP file gives you your documents exactly as they were.
Related: Compression, ZIP
Learn more: ZIP files: compressing and extracting
A unique number built into a network interface that identifies it on the local network.
Example: A laptop's Wi-Fi card might be 3C:52:82:1A:9B:07, and the router sees that number for every message it sends.
Related: Network, IP address
Learn more: Routers, switches, modems, access points, Ethernet and Wi-Fi
A way of building software that learns patterns from many examples instead of following rules a person wrote.
Example: A photo app learns to spot faces after being shown millions of pictures that people have labelled.
Related: Artificial intelligence, Large language model
Learn more: What AI is and how it learns
A macro is a small program stored inside a document or spreadsheet that can run automatically.
Macros can save time, but criminals also use them to install malware. Do not enable macros in files you did not expect.
Example: An email attachment that asks you to enable macros to see an invoice is a warning sign.
Related: Malware, Phishing, Spreadsheet
Learn more: Charts and spreadsheet safety
The high-voltage electricity from the wall sockets in your home.
Example: In the UK mains power is about 230 volts, which is dangerous if you touch it.
Related: Power supply
Learn more: Hardware faults and what not to repair yourself, Power, cooling and the display
A short list of regular checks, such as updates, storage tidy-up and backup tests, done on a schedule.
Example: Ten minutes on the first Sunday of the month to update, check space and open one backed-up file.
Related: Restore test, Software Updater
Learn more: A safe maintenance routine
Any software made to harm your device, steal your information or spy on you.
Example: A fake game installer that quietly records everything you type is malware.
Learn more: Microsoft Store, Windows Update and Windows Security
The built-in manual page for a command, opened with man and closed with q.
Example: man ls shows every option of ls.
Related: Permission string
Learn more: Permissions, getting help, sudo and packages
The empty space between the edge of the page and the text.
Example: A letter with 2.5 cm margins leaves a clear border all round so nothing is cut off when it is printed.
Related: Line spacing, Word processor
Learn more: Headings, margins, lists, headers, footers and page numbers
A CSS block whose rules apply only when a condition, such as the screen being wide enough, is true.
Example: @media (min-width: 40rem) { ... } applies from 40rem upwards.
Related: Responsive design, CSS
Learn more: Responsive design, media queries, hover and focus states
A million bits; internet speeds are quoted in megabits per second, and eight bits make one byte.
Example: A 40 Mbps connection moves about 5 megabytes of data each second at best.
Learn more: Packets, protocols, bandwidth and latency
A small removable card that stores files such as photos and music.
Example: A phone's microSD card holds the photos so they can be moved to a laptop with a card reader.
Learn more: USB drives, external drives, safe ejection and formatting
A fault in which a program keeps using more memory over time and does not give it back.
Example: A program whose memory use climbs steadily while you are not doing anything in it.
Related: System Monitor, Task Manager
Learn more: Resource monitoring, startup applications and when to seek repair
Hidden details stored inside a file about the file itself, such as who made it and when.
Example: A photo can carry the date it was taken and the place, so you should check before sharing it.
Learn more: Scanning, image quality, OCR and safe sharing
The built-in Windows shop where you can find and install apps checked by Microsoft.
Example: Opening the Store, searching for a notes app and pressing Get installs it without visiting a website.
Related: Application, Windows Update
Learn more: Microsoft Store, Windows Update and Windows Security
The smallest set of steps or the shortest code that still shows a problem.
Example: Instead of sending a whole project, you show the one command that fails and its exact output.
Related: Error message, Debugging
Learn more: Asking precise questions, recording solutions and knowing when to get help
Misinformation is false or misleading information that is shared, whether or not the person sharing it meant to deceive.
When someone spreads falsehoods on purpose it is often called disinformation. Either way, check before you believe or share.
Example: A forwarded message claims a common medicine cures every illness; no health body says so.
Related: lateral reading, primary source, Hallucination
Learn more: Evaluating sources and spotting misinformation
The result of training: a large set of numbers that captures the patterns found in the training examples.
Example: A model trained on many labelled photos that can then guess whether a new photo shows a cat.
Related: Machine learning, Training data
Learn more: What AI is and how it learns
A box that turns the signal from your internet provider's line into one your router can use.
Example: The small box where the fibre cable enters the house is the modem, and the router plugs into it.
Learn more: What is a network?
A key such as Ctrl, Shift or Alt that changes what another key does when you hold it down at the same time.
Example: Holding Shift while pressing a letter gives a capital letter.
Related: Keyboard shortcut
Learn more: The keyboard and essential shortcuts
The main circuit board that every other part of the computer plugs into.
Example: The processor, memory and storage all connect to the motherboard inside a desktop case.
Learn more: Inside the computer: CPU, RAM, motherboard and graphics
The place in the folder tree where a disk or partition is attached and becomes usable.
Example: The main disk is mounted at /, and a USB drive may appear under /media.
Related: Swap space
Learn more: Looking at the system: df, du, free, ps, top, whoami and id
Signing in with your password plus a second proof, such as a code from your phone.
Example: After typing her password, Grace enters a six-digit code sent to her phone before the account opens.
Related: Passphrase, Recovery code
Learn more: Spam, phishing, password recovery and email account security
An agreed pattern for naming files so they are easy to find and sort.
Example: 2025-03-14_budget_event_v02.xlsx: date, topic, detail, version.
Related: Version control, File extension
Learn more: File naming, document organisation and version control concepts
The polite, considerate way of behaving in email, chat and online meetings.
Example: Muting your microphone when you are not speaking in a video call.
Related: Bcc
Learn more: Professional email, online meetings and etiquette
Two or more devices joined together so they can share information.
Example: The phones, laptops and printer in a home all join the same network through the router.
Learn more: What is a network?
The router's trick of letting many private devices share one public address.
Example: Four phones in one house all reach the internet through the router's single public address.
Related: Private IP address, Public IP address, Router
Learn more: IP addresses: IPv4, IPv6, public and private
The part of a device, a chip or a card, that lets it join a network by cable or radio.
Example: A laptop has a Wi-Fi interface, and may also have an Ethernet interface for a cable.
Related: Ethernet, Wi-Fi, MAC address
Learn more: Routers, switches, modems, access points, Ethernet and Wi-Fi
A numbered door on a computer that tells it which program should receive incoming data.
Example: Web pages over HTTPS arrive at port 443.
Related: TCP, UDP, IP address
Learn more: Ports, TCP and UDP, ping and traceroute
A box with many cable sockets that passes messages between the devices plugged into it.
Example: An office uses a switch so ten desktop computers can all connect to one router.
Learn more: Routers, switches, modems, access points, Ethernet and Wi-Fi
A short message that a program shows on your screen, such as a new email or an available update.
Example: A banner at the top of the screen saying that an update is ready.
Related: App permission
Learn more: Privacy permissions, notifications and application defaults
The standard file system that Windows uses on its main drive.
Ubuntu can read and write NTFS drives, but some other devices, such as many cameras and televisions, cannot.
Example: The C: drive on a Windows laptop is formatted as NTFS.
Related: File system, ext4, exFAT
Learn more: File systems and software compatibility
A number format changes how a value looks in a cell without changing the value.
Formats include currency, percent, decimal places and dates. Open Format Cells with Ctrl+1 in Calc and Excel.
Example: The value 1500 shown as KSh 1,500.00 is still the number 1500.
Related: data type, cell, Spreadsheet
Learn more: Spreadsheet basics: cells, rows, columns and data types
A collection of named values kept together, written with curly brackets.
Example: { name: "Amina", age: 31 } has two properties, name and age.
Learn more: JavaScript basics: variables, conditions, loops, functions, arrays and objects
Software that reads the letters in a picture of a page and turns them into text you can edit and search.
Example: After scanning a printed letter, OCR lets you copy its words into a document.
Related: PDF, Scan resolution
Learn more: Scanning, image quality, OCR and safe sharing
One of the four numbers in an IPv4 address; each runs from 0 to 255.
Example: In 192.168.1.20 the octets are 192, 168, 1 and 20.
Learn more: IP addresses: IPv4, IPv6, public and private
Offline access means being able to open a file or app without an internet connection, because a copy is stored on the device.
Many cloud services only keep a file on the device if you choose to make it available offline.
Example: Kamau marks his notes as available offline before a long bus journey.
Related: local copy, Sync, Cloud storage
Learn more: Cloud storage, synchronisation and local vs cloud copies
A picture of a keyboard shown on the screen that you click or tap instead of using physical keys.
Example: Useful when a physical key is broken or typing is difficult.
Related: Input device, Accessibility
Learn more: Accessibility, zoom and comfortable use
A free, openly published way of saving documents that many programs can open.
Example: A report saved as report.odt opens in LibreOffice and can also be opened in other word processors.
Related: LibreOffice, DOCX file
Learn more: Writing your first document in LibreOffice Writer
Software whose instructions are public, so anyone may read, use and often improve it.
Example: Linux and LibreOffice are open source, so you can download them without paying.
Related: Licence, Operating system
Learn more: What an operating system does
The main software that runs the computer and lets you and your apps use its parts.
Example: Windows and Ubuntu are operating systems; without one the computer cannot run any app.
Related: Kernel, Application
Learn more: What happens when a computer starts
A download that fixes problems and security holes in the main software of your computer.
Example: Windows restarts overnight to finish installing its monthly update.
Related: Update, Operating system
Learn more: User accounts, permissions, updates and drivers
An extra word added to a command, often starting with a dash, that changes how the command works.
Example: In ls -l the -l option asks for a longer, more detailed list of files.
Learn more: Terminal, shell and your first commands
The main server that holds the original copy of a website, which a CDN copies from.
Example: A CDN fetches a photo once from the origin server and then serves copies from nearby.
Related: CDN, Web server
Learn more: Web servers, hosting, CDNs, cookies and sessions
A device the computer uses to show or give you its results.
Example: A screen, speakers, a printer.
Related: Input device
Learn more: What is a computer?
To replace an existing file with new contents so the old contents are lost.
Example: cp new.txt old.txt replaces old.txt without asking unless you add -i.
Related: Recursive
Learn more: Making, copying and moving: mkdir, touch, cp and mv
A service where the provider runs the servers and system and you only supply your own application and data.
Example: A host that runs your web application code without you managing any server.
Learn more: Web applications and service models
A bundle of software files, with instructions for installing them, that a package manager can add or remove.
Example: On Ubuntu, the package called vlc contains the VLC media player.
Related: Package manager, Deb package
Learn more: Processes, services, packages and logs
A tool that finds, installs, updates and removes software for you from trusted sources.
Example: On Ubuntu, apt is a package manager: you type its install command and it fetches the program.
Related: Repository, Package
Learn more: Installing and removing software on Ubuntu
A small piece of data sent across a network, labelled with where it came from and where it is going.
Example: A photo you send is cut into many packets that travel separately and are put back together.
Learn more: Packets, protocols, bandwidth and latency
When some packets never arrive, so data has to be sent again or is missing.
Example: A video call freezes and stutters because a weak Wi-Fi signal is dropping packets.
Learn more: Packets, protocols, bandwidth and latency
Whether a page is laid out tall (portrait) or wide (landscape).
Example: A wide table prints better in landscape orientation than portrait.
Related: Print preview, Page range
Learn more: PDFs, print preview and printing
The choice of which pages of a document to print or export.
Example: Typing 2-4 in the print box prints only pages two, three and four.
Related: Print preview, Duplex printing
Learn more: PDFs, print preview and printing
The one-time introduction in which two Bluetooth devices agree to trust and connect to each other.
Example: Holding a speaker's button until it flashes, then choosing it in the laptop's Bluetooth list.
Related: Airplane mode
Learn more: No internet, printer failures, Bluetooth and sound problems
A saved set of formatting, such as font and spacing, that you apply to a whole paragraph in one click.
Example: Applying the Heading 1 style to a title makes it large and bold, like every other main heading.
Related: Font, Line spacing
Learn more: Headings, margins, lists, headers, footers and page numbers
A sign-in method that replaces the password with a key held on your device and unlocked by your fingerprint, face or screen lock.
Example: Amina signed in to her account with her fingerprint instead of typing a password.
Related: Multifactor authentication (MFA), Screen lock
Learn more: Multifactor authentication, recovery codes and sessions
A long password made of several unrelated words, which is hard to guess yet easy to remember.
Example: "green kettle bicycle sunrise" is a stronger passphrase than "Password1".
Related: Password manager, Multifactor authentication (MFA)
Learn more: Spam, phishing, password recovery and email account security
An app that stores all your passwords safely and fills them in for you, so you remember only one.
Example: Instead of reusing one password, Peter lets his password manager make a different strong one for each site.
Related: Passphrase, Multifactor authentication (MFA)
Learn more: Making a backup plan and testing a restore
A list of folders the computer searches when you type the name of a program in the terminal.
Example: Typing python works because the folder that holds Python is listed in PATH.
Related: Environment variable, Terminal
Learn more: The filesystem hierarchy, environment variables and shell scripts
A file type that keeps a document looking the same on every device.
Example: A CV saved as a PDF keeps its layout whether it is opened on a phone or a laptop.
Related: OCR (optical character recognition), Print preview
Learn more: Files, folders, names and extensions
A way of connecting in which two devices talk as equals instead of one being a client and one a server.
Example: Two phones send a photo straight to each other over a local wireless link.
Learn more: What is a network?
Testing a system's security by carefully trying to break in, only with the owner's written permission.
Example: A company hires a tester, under a signed agreement, to check whether its own website can be broken into.
Related: Vulnerability, Authorisation
Learn more: Authentication, network security and safe lab practice
A device that connects to a computer from outside to add input or output.
Example: A mouse, a printer, a webcam or a pair of speakers.
Related: Input device, Output device, USB
Learn more: Ports, cables and peripherals
A rule that says who may read, change or run a file or use a feature.
Example: A shared folder may let your sister read the files but not delete them.
Related: User account, Administrator
Learn more: User accounts, permissions, updates and drivers
The ten characters at the start of an ls -l line that show a file's type and who may read, write or run it.
Example: -rw-rw-r-- is an ordinary file the owner and group can change and others can only read.
Related: Execute permission, Group
Learn more: Permissions, getting help, sudo and packages
Any information that identifies you or could be used to identify you.
Example: Your name, phone number, address, photo and ID number are all personal data.
Related: Digital footprint, Identity theft
Learn more: Personal information and your digital footprint
Your own organised collection of notes about problems you solved and how.
Example: A folder of short text files, one for each fix, with the date, the symptom and the steps that worked.
Related: Naming convention, Error message
Learn more: Asking precise questions, recording solutions and knowing when to get help
A trick message that pretends to be from a trusted source to make you give away passwords or money.
Example: An email claiming to be your bank asks you to click a link and confirm your PIN.
Related: Social engineering, Malware
Learn more: HTTPS and spotting suspicious websites
A test that sends a tiny message to another computer and waits for a reply, to show whether the path to it works.
Example: ping -c 4 192.168.1.1 tests whether your laptop can reach the router.
Related: Power cycle
Learn more: No internet, printer failures, Bluetooth and sound problems
The | symbol, which passes the output of one command to another as its input.
Example: ls | wc -l counts how many items ls listed.
Related: grep
Learn more: Reading and searching: file, cat, less, head, tail, grep and find
One tiny dot of colour on a screen. A picture is a grid of thousands or millions of them.
Example: A screen that is 1920 pixels wide and 1080 pixels high has about two million pixels.
Related: Resolution, Binary
Learn more: How computers process information, Power, cooling and the display
Plagiarism is presenting someone else's words, ideas or work as if they were your own.
It is about honesty and credit. Quoting or paraphrasing with a clear acknowledgement is not plagiarism; copying without credit is, even if the work is free to use.
Example: Pasting two paragraphs from a website into an essay without quotation marks or a source is plagiarism.
Related: citation, copyright, primary source
Learn more: Copyright, plagiarism and citing sources
The small arrow on the screen that moves when you move the mouse or slide a finger on the touchpad.
Example: You move the pointer over a button and click to press it.
Related: Touchpad, Input device
Learn more: Mouse and touchpad skills
A socket on a computer where you plug in a cable or a device.
Example: A laptop may have a USB port for a flash drive and an HDMI port for a screen.
Learn more: Ports, cables and peripherals
A small collection of your own work that shows what you can do.
Example: A folder with a fault guide, a network map and a one-page runbook.
Related: Certification
Learn more: Next steps: IT support, networking and Linux administration
Switching a device fully off, waiting briefly and switching it on again to clear a stuck state.
Example: Unplugging a router for 30 seconds, then plugging in the modem first and the router second.
Related: Ping
Learn more: No internet, printer failures, Bluetooth and sound problems
The part that changes the electricity from the wall into the lower, steady voltages that the computer needs.
In a desktop it is a metal box inside the case. In a laptop it is the charger brick plus circuits inside the laptop.
Example: The charger brick that comes with a laptop.
Related: Lithium-ion battery, Mains power
Learn more: Power, cooling and the display, Hardware faults and what not to repair yourself
A quick check the firmware runs at start-up to see that the memory, processor and other basics respond.
Example: If a memory stick is missing, a desktop may beep or flash a light instead of showing anything on screen.
Learn more: What happens when a computer starts
A powerful Windows text tool where you type commands to control the computer.
Example: Typing Get-ChildItem in PowerShell lists the files in the current folder.
Related: Cmdlet, Windows Terminal
Learn more: Command Prompt and PowerShell
A screen only the speaker sees, showing the next slide, notes and a timer while the audience sees the slides.
Example: While the projector shows slide 3, Mary's laptop shows her notes and a preview of slide 4.
Related: Speaker notes, Slide
Learn more: Presenting, accessibility, exporting and sharing
A primary source is the original evidence or the body that first published the information, such as a law, a data table or an official notice.
A secondary source, such as a news report or a blog, tells you about the primary source. Where you can, go back to the original.
Example: A news story quotes a figure; the statistics office's own table is the primary source.
Related: misinformation, lateral reading, citation
Learn more: Evaluating sources and spotting misinformation
A view that shows how a document will look on paper before you print it.
Example: Checking print preview reveals that the last column would spill onto a second page.
Related: Page orientation, Page range
Learn more: PDFs, print preview and printing
The waiting list of documents sent to a printer, printed in order.
Example: A stuck first job holds up every document behind it until you cancel it.
Related: Pairing
Learn more: No internet, printer failures, Bluetooth and sound problems
A document in which a company says what information it collects and what it does with it.
Example: Before signing up, Fatuma skimmed the privacy policy for what the app shares with others.
Related: Personal data, Data broker
Learn more: Personal information and your digital footprint
Private browsing is a window that does not save history or cookies on your device once you close it.
It does not hide you from websites, your employer, your school or your internet provider. It only leaves less behind on that one device.
Example: Wanjiru uses a private window on a library computer so her history is not kept there.
Related: browsing history, Cookie, Browser
Learn more: History, cookies, cache, private browsing and permissions
An address used only inside a home or office network, which is not reachable directly from the internet.
Example: 192.168.1.20 and 10.0.0.5 are private addresses; many homes use the same ones.
Related: Public IP address, Network address translation (NAT), IPv4
Learn more: IP addresses: IPv4, IPv6, public and private
A program that is currently running, together with the memory and resources it is using.
Example: Each open browser window or music player appears as a process in the task manager.
Related: Operating system, Application
Learn more: What an operating system does
The number, also called a PID, that identifies one running process.
Example: ps shows PID 2417 next to a program so tools can refer to that exact program.
Related: Swap space
Learn more: Looking at the system: df, du, free, ps, top, whoami and id
A list of instructions that tells a computer how to do a job.
Example: A calculator app is a program that follows instructions for adding, subtracting and showing results.
Related: Instruction, Software
Learn more: How computers process information
A short written request that says what is wanted, for whom, in what form and by when.
Example: A page asking a volunteer for a one-page report, a spreadsheet and five slides by Friday.
Related: Deliverable
Learn more: Project, part 1: research a topic and organise your materials
The short text in a terminal that shows it is ready and waiting for you to type a command.
Example: On Ubuntu the prompt may read grace@laptop:~$ before the cursor.
Learn more: Terminal, shell and your first commands
The text you give an AI tool so it knows what to produce.
Example: Explain the SUM function to a beginner in four steps.
Related: Generative AI, Large language model
Learn more: Writing prompts and checking what AI tells you
Software whose source code is kept private and whose use is controlled by its owner.
Example: Windows is proprietary; Ubuntu is open-source.
Related: Open source, Licence
Learn more: Default apps, file associations, licences and browser extensions
A set of agreed rules that devices follow so they can understand each other.
Example: Web pages travel using the HTTP protocol, and email uses different protocols.
Learn more: Packets, protocols, bandwidth and latency
A plan for a program written in plain, everyday words instead of a real programming language.
Example: IF it is raining THEN show Take an umbrella.
Learn more: Algorithms, sequencing, pseudocode and flowcharts
The address your network shows to the internet, normally given by your provider.
Example: Websites see the public address of your router, not the private address of your phone.
Related: Private IP address, Internet service provider (ISP), Network address translation (NAT)
Learn more: IP addresses: IPv4, IPv6, public and private
A square pattern that stores data, usually a web address, which a phone camera can read.
Example: Scanning the code on the poster opened the cafe's menu page.
Learn more: Payment fraud, QR codes, online shopping and reporting scams
Phishing that uses a QR code to send you to a fake site.
Example: A sticker placed over a parking-meter code led to a fake payment page.
Learn more: Payment fraud, QR codes, online shopping and reporting scams
Putting quotation marks around text in a command so the shell treats it as one piece.
Example: cd "My Photos" works with the space in the name, but cd My Photos would fail.
Learn more: Paths, case sensitivity, quoting, history and tab completion
The computer's short-term working space, which holds what you are using right now and is emptied when it switches off.
Example: Opening many browser tabs uses a lot of RAM and can make an older laptop slow.
Learn more: Inside the computer: CPU, RAM, motherboard and graphics
Malware that locks your files and demands money to unlock them.
Example: A message says all your photos are scrambled unless you pay; a recent backup means you need not pay.
Learn more: Why backups matter and the ways data is lost
The order in which a screen reader reads the items on a slide or page.
Example: If the picture comes before the title in the reading order, a blind listener hears them the wrong way round.
Related: Screen reader, Alt text
Learn more: Presenting, accessibility, exporting and sharing
A one-time code, saved safely, that lets you get back into an account if you lose your phone or second step.
Example: Ruth prints her recovery codes and keeps them in a drawer in case her phone is stolen.
Related: Multifactor authentication (MFA), Password manager
Learn more: Spam, phishing, password recovery and email account security
Applied to a folder and everything inside it, including folders within folders.
Example: cp -r projects projects-copy copies the folder and all its contents.
Related: Overwrite
Learn more: Making, copying and moving: mkdir, touch, cp and mv
Permanently removing private details, such as names or numbers, from a document before sharing it.
Example: Before sharing a scan, Daniel properly removes his account number rather than just drawing a black box over it.
Learn more: Scanning, image quality, OCR and safe sharing
How many times per second the screen redraws the picture, measured in hertz (Hz).
Example: A 60 Hz screen redraws sixty times a second; a 120 Hz screen redraws twice as often.
Related: Resolution, Display panel
Learn more: Power, cooling and the display
A file location described starting from the folder you are in now.
Example: From Documents, the relative path Reports/may.txt reaches a file in the Reports folder.
Related: Absolute path, File path
Learn more: Folder hierarchies and file paths
A relative reference is a cell address that changes when the formula is copied to another cell.
It keeps the same position relative to the formula. A formula in D2 that says C2-B2 becomes C3-B3 when copied to D3.
Example: Filling =C2-B2 down a column gives each row its own calculation.
Related: absolute reference, Cell reference, Formula
Learn more: Formulas, functions and cell references
A list written by the makers of software that says what changed in a version.
Example: Notes that say a setting moved to a different menu in the newest version.
Related: Documentation, Operating system update
Learn more: Reading documentation and searching for error messages
An online store of software or project files that tools can download from.
Example: Ubuntu's package manager downloads programs from its official repositories.
Related: Package manager, Git
Learn more: Installing and removing software on Ubuntu
The number of pixels a screen shows across and down. More pixels means finer detail.
Example: 1920 by 1080 pixels is called Full HD.
Related: Pixel, Display panel
Learn more: Power, cooling and the display
The operating system's job of sharing the processor, memory, storage and devices fairly between all running programs.
Example: When a browser and a music player both need memory, the operating system decides how much each gets.
Related: Operating system, Process
Learn more: What an operating system does
Building a web page so its layout adapts to the size of the screen it is shown on.
Example: A menu that stacks on a phone and sits in a row on a laptop.
Related: Media query, CSS
Learn more: Responsive design, media queries, hover and focus states
To copy files back from a backup to your computer after they were lost or damaged.
Example: After deleting a folder by mistake, Fatuma restored it from her external drive.
Related: Backup, Version history
Learn more: Making a backup plan and testing a restore
A practice run in which you bring files back from a backup to prove that the backup really works.
Example: Once a month Amina restores one folder from her backup drive into a test folder and opens the files.
Related: Backup, Retention policy
Learn more: Services, logs, storage and backups for administrators
Opening a real file from your backup to prove the backup works and can be read.
Example: Once a month, Amina opens last week's CV from the backup drive to check that it is complete.
Related: Maintenance routine
Learn more: A safe maintenance routine
A rule that says how long backups or logs are kept before they are deleted.
Example: Keep daily backups for two weeks and monthly backups for a year.
Learn more: Services, logs, storage and backups for administrators
The chance that a threat will use a weakness, together with how bad the harm would be.
Example: Using public Wi-Fi to log in to a bank carries more risk than reading the news there.
Related: Threat, Vulnerability
Learn more: Threats, vulnerabilities, risks and malware
A scam in which someone builds an online relationship to get money from you.
Example: A person Fatuma never met asked for money for a hospital bill.
Related: Scam, Social engineering
Learn more: Common scams: jobs, investments, impersonation and romance
The all-powerful account on Linux, or the top folder of the file system, depending on context.
Example: Running a command as root lets it change system files, so be careful; the top folder is written /.
Related: sudo, Administrator
Learn more: Terminal, shell and your first commands
How long a message takes to reach another computer and for the reply to come back.
Example: A ping reply that says time=24 ms took 24 thousandths of a second to go there and back.
Learn more: Ports, TCP and UDP, ping and traceroute
A device that connects your home network to the internet and shares that connection with your devices.
Example: Everyone at home reaches the internet through the one router in the living room.
Learn more: Ubuntu Settings: network, Bluetooth, display, sound and printers
A list inside a device that says which way to send data for each destination.
Example: The table says: for anything not on my own network, send it to the gateway 192.168.1.1.
Related: Default gateway, Router
Learn more: Network settings and diagnostic tools
Software you use through a browser or app while the provider runs and maintains everything behind it.
Example: Online email or an online word processor.
Learn more: Web applications and service models
Telling the computer to finish writing to a drive so you can unplug it without damaging files.
Example: Right-clicking the USB drive and choosing Eject before pulling it out.
Related: USB, Memory card
Learn more: USB drives, external drives, safe ejection and formatting
A trick to get your money or details by making you believe something false.
Example: A message offering a prize if you pay a small fee is a scam.
Related: Phishing, Social engineering
Learn more: Common scams: jobs, investments, impersonation and romance
How much detail a scanner captures, usually counted in dots per inch.
Example: 300 DPI is enough to read a printed page; 1200 DPI makes much larger files.
Related: OCR (optical character recognition), PDF
Learn more: Scanning, image quality, OCR and safe sharing
A password, PIN or fingerprint needed to use a device after it sleeps or is switched on.
Example: Fatuma's phone asks for a PIN each time the screen turns on.
Related: Passkey, User account
Learn more: Multifactor authentication, recovery codes and sessions
A feature that enlarges part of the screen so small text and details are easier to see.
Example: Holding a key and scrolling the mouse wheel to zoom in on a small label.
Related: High contrast, Accessibility
Learn more: Accessibility, zoom and comfortable use
Software that reads aloud what is on the screen, helping people who cannot see it well.
Example: A blind student uses a screen reader to hear emails and menus spoken.
Related: Accessibility, Alt text
Learn more: Accessibility, zoom and comfortable use
A picture of what is showing on your screen.
Example: Pressing the Print Screen key saves a picture of the error message to show a helper.
Related: File, Troubleshooting
Learn more: Updates, screenshots and USB drives on Ubuntu
A text file of instructions that the computer follows in order, so a job can be repeated easily.
Example: A short script can copy your documents to a backup drive every Friday.
Learn more: The filesystem hierarchy, environment variables and shell scripts
A search engine is a website that keeps a huge index of web pages and shows you the ones that best match the words you type.
It does not search the whole web live. It searches its own index, so results can be out of date, ranked by its own rules, or mixed with adverts.
Example: Typing bus timetable Nairobi into a search engine returns a ranked list of pages.
Related: Browser, search query, sponsored result
Learn more: How a web browser works for you, Searching well: queries and operators
A search operator is a small symbol or word, such as quotation marks or a minus sign, that tells a search engine exactly how to treat your words.
Common ones are quotation marks for an exact phrase, a minus sign to exclude a word, site: to limit results to one website and filetype: to find one kind of file. Search engines differ slightly, so test them.
Example: "password manager" -ads site:example.org looks for that exact phrase, without the word ads, only on example.org.
Related: search engine, search query
Learn more: Searching well: queries and operators
A search query is the words you type into a search engine to say what you want to find.
Example: The query how to attach a file to an email gives better results than the query email.
Related: search engine, search operator
Learn more: Searching well: queries and operators
A setting that starts in the safe position, so no one has to remember to make it safe.
Example: A new Wi-Fi router that asks you to set your own password instead of using a published one.
Related: Attack surface, Password manager
Learn more: Threat modelling and secure configuration
A small update that fixes a weakness attackers could use to break into your computer.
Example: A monthly Windows update that closes a hole in the web browser engine.
Related: Operating system update, Malware
Learn more: User accounts, permissions, updates and drivers
HTML elements whose names say what a part of the page is for, such as header, nav, main and footer.
Example: Using nav for the menu links instead of an anonymous div.
Related: HTML, Accessibility
Learn more: Tables, forms, semantic structure and accessibility
A computer that holds information or services and sends them to other devices that ask.
Example: When you open a website, a server somewhere sends the page to your browser.
Related: Client, Web server
Learn more: Email basics: addresses, inbox, To, CC and BCC
A program that runs in the background, often from start-up, to provide something such as printing or web pages.
Example: The ssh service waits in the background so an administrator can log in from another computer.
Learn more: Services, logs, storage and backups for administrators
The period during which a site remembers that you have signed in.
Example: Kamau closed the tab without signing out, so his session stayed active on the library computer.
Learn more: Multifactor authentication, recovery codes and sessions
The program in a terminal that reads the commands you type and carries them out.
Example: Bash is a common shell on Ubuntu; it runs whatever you type after the prompt.
Related: Terminal, Command line
Learn more: Terminal, shell and your first commands
A text file of commands that the shell runs in order, so you can repeat a job with one command.
Example: A file called rename.sh that adds a prefix to every report file in a folder.
Related: Shell, Automation
Learn more: Your first simple shell scripts
How strong the radio signal from the router is where you are, often shown as bars.
Example: One bar in the far bedroom means a weak signal and slow, unreliable Wi-Fi.
Related: Wi-Fi, Interference
Learn more: Wi-Fi signal, router restarts and firewalls: diagnosing step by step
A site permission is a setting that decides whether one website may use your location, camera, microphone or notifications.
Browsers ask the first time a site wants one. You can review and remove permissions later in the browser settings.
Example: A map site asks to know your location; Amina chooses Block.
Related: Permission, Browser, Cookie
Learn more: History, cookies, cache, private browsing and permissions
A low-power state that pauses the computer so it wakes quickly with your work still open.
Example: Closing a laptop lid puts it to sleep, and opening it brings back your document at once.
Related: Hibernation, Boot
Learn more: What happens when a computer starts
One page of a presentation.
Example: A talk with ten slides shows one idea on each.
Related: Slide layout, Theme
Learn more: Building slides: layouts, themes and content
The arrangement of title, text and pictures on a slide.
Example: Choosing the Title and Content layout gives a heading with a bullet list below it.
Learn more: Building slides: layouts, themes and content
A built-in health report that a drive keeps about itself, which software can read to warn you of trouble.
Example: A disk-health tool may say the drive is Healthy or warn that it has reallocated sectors.
Related: SSD (solid-state drive), Hard disk, Backup
Learn more: Storage devices: SSD, hard disk, USB drives and memory cards, Hardware faults and what not to repair yourself
A Windows safety check that warns you before you open files or sites that look unsafe.
Example: A blue warning appears when you try to run a downloaded program Microsoft does not recognise.
Related: Malware, Windows Update
Learn more: Microsoft Store, Windows Update and Windows Security
Phishing sent as a text message.
Example: A text said a parcel was held and asked Kamau to pay a fee through a link.
Learn more: Threats, vulnerabilities, risks and malware
An Ubuntu software bundle that carries everything the app needs, so it runs the same on different systems.
Example: Some apps in the Ubuntu app store are installed as snaps.
Related: Package, App Center
Learn more: Installing and removing software on Ubuntu
The instructions that tell hardware what to do. You cannot touch it.
Software includes the operating system, applications and the files and settings they use.
Example: A web browser, a word processor, Ubuntu or Windows.
Related: Hardware
Learn more: What is a computer?
The Ubuntu tool that checks for and installs updates to the system and its programs.
Example: Software Updater opens with a list of updates and an Install Now button.
Related: Temporary file
Learn more: Failed updates, display problems, overheating, battery and permission errors, A safe maintenance routine
Sorting puts the rows of a list in order, such as A to Z or smallest to largest.
Sorting must move whole rows so each record stays together. Click inside a tidy table with a heading row and save a copy first.
Example: Sorting a stock list by quantity puts the lowest stock at the top.
Related: filtering, Spreadsheet, data validation
Learn more: Sorting, filtering and data validation
Spam is unwanted email sent in bulk, usually advertising or scams.
Email providers use spam filters to move it to a Spam or Junk folder. Some spam is harmless advertising and some is phishing.
Example: A message promising a free holiday from an unknown sender lands in the Spam folder.
Related: Phishing, inbox, spoofing
Learn more: Spam, phishing, password recovery and email account security
Private notes attached to a slide that only the presenter sees.
Example: Under each slide Lucy writes the main points she wants to say aloud.
Related: Presenter view, Slide
Learn more: Building slides: layouts, themes and content
A tool that marks words that may be spelled wrongly.
Example: A red wavy line under recieve suggests the correct spelling, receive.
Related: Word processor, Track changes
Learn more: Tables, images, checking, track changes and exporting to PDF
A sponsored result is a search result that a company paid to have shown, usually marked with a label such as Sponsored or Ad.
It can look just like a normal result. Being paid for does not make it wrong, but it does not make it the best answer either.
Example: The first link on the page is marked Sponsored, so Kamau scrolls down to the unpaid results.
Related: search engine, misinformation
Learn more: Searching well: queries and operators
Spoofing is faking the sender of a message so that it appears to come from someone you trust.
The name shown can be set to anything. Checking the real address, and contacting the sender by another route, protects you.
Example: A message shows the display name of Joseph's bank but comes from an unrelated address.
Related: Phishing, email address, spam
Learn more: Spam, phishing, password recovery and email account security
A grid of rows and columns for keeping numbers and text and doing sums on them.
Example: A monthly budget in a spreadsheet adds up your spending automatically.
Related: Formula, Cell reference
Learn more: Spreadsheet basics: cells, rows, columns and data types
Malware that secretly watches what you do and sends the details to someone else.
Example: A free toolbar that records every website you visit is spyware.
Learn more: Threats, vulnerabilities, risks and malware
A fast storage device with no moving parts that keeps your files when the power is off.
Example: Swapping a slow old hard disk for an SSD makes a laptop start up much faster.
Learn more: Storage devices: SSD, hard disk, USB drives and memory cards
The name a Wi-Fi network shows in the list of available networks.
Example: Wanjiru's router broadcasts an SSID called HomeNet-Wanjiru.
Related: Wi-Fi, Access point
Learn more: Wi-Fi signal, router restarts and firewalls: diagnosing step by step
An account that can use programs and change its own files and settings, but cannot change the whole computer.
Example: A standard user cannot install software for everyone without an administrator's approval.
Related: Administrator, Permission
Learn more: User accounts, permissions, updates and drivers
A program that starts by itself every time you sign in to the computer.
Example: A chat app that opens on its own and slows the start by several seconds.
Related: Task Manager, System Monitor
Learn more: Resource monitoring, startup applications and when to seek repair
A small build-up of electric charge on your body that can jump to metal as a spark.
It is harmless to you but can damage delicate computer chips.
Example: The little shock you feel after walking across a nylon carpet and touching a door handle.
Related: Hardware
Learn more: Hardware faults and what not to repair yourself
A website made of ready-written files (HTML, CSS, JavaScript, images) that the server sends unchanged.
Example: A personal page with index.html and style.css on a free static host.
Related: Web server, Hosting
Learn more: Final project: build and publish a personal web page
An accessibility setting that lets you press shortcut keys one after another instead of holding them all at once.
Example: Press Ctrl, let go, then press C, and the computer treats it as Ctrl and C together.
Related: Modifier key, Keyboard shortcut
Learn more: Accessibility, zoom and comfortable use
The part of a computer that keeps your files and programs even when it is switched off.
Example: A laptop with 256 GB of storage can hold thousands of photos and documents.
Related: RAM, SSD (solid-state drive)
Learn more: Inside the computer: CPU, RAM, motherboard and graphics
A storage quota is the amount of space that a cloud service lets your account use.
Free accounts usually have a small quota. When it is full, new files may stop syncing and email may stop arriving.
Example: Fatuma sees a message that she has used 14.8 GB of her 15 GB quota and deletes old videos.
Related: Cloud storage, Sync, Gigabyte
Learn more: Cloud storage, synchronisation and local vs cloud copies
A piece of text in a program, written between quotation marks.
Example: The text "Hello, Amina" is a string.
Learn more: Variables, data types, conditions, loops and functions
A prefix added to a domain name to name a separate section or service of a site.
Example: In mail.example.org, mail is a subdomain of example.org.
Related: Domain name, Top-level domain (TLD)
Learn more: Domains, URLs, HTTP and HTTPS
A group of addresses that belong to the same local network and can reach each other directly.
Example: All devices from 192.168.1.1 to 192.168.1.254 can be one subnet.
Related: Subnet mask, IP address, Default gateway
Learn more: IP addresses: IPv4, IPv6, public and private
A number such as 255.255.255.0 that tells a device which part of an address names the network.
Example: With the mask 255.255.255.0, addresses that share the first three numbers are on the same subnet.
Learn more: IP addresses: IPv4, IPv6, public and private
A payment every month or year for continued use of software or a service.
Example: An office suite that stops editing features if you stop paying.
Learn more: Default apps, file associations, licences and browser extensions
A command word that runs the next command with administrator power, after asking for your password.
Example: sudo apt update asks for your password and then refreshes the software lists.
Related: Root, Administrator
Learn more: Users, groups and permissions in depth
Disk space the system uses as slow overflow when memory is full.
Example: free -h shows how much swap is in use; a lot of swap in use suggests memory is short.
Related: Mount point
Learn more: Looking at the system: df, du, free, ps, top, whoami and id
Keeping the same files up to date on more than one device or place.
Example: A photo taken on your phone appears on your laptop because both sync with the same account.
Related: Cloud storage, Backup
Learn more: Why backups matter and the ways data is lost
A sync conflict happens when the same file is changed in two places before they could sync, so the service keeps both versions.
Example: Fatuma edited a file on her laptop while offline and on her phone; the service saved a second copy marked conflicted.
Related: Sync, Version history, local copy
Learn more: Cloud storage, synchronisation and local vs cloud copies
A mistake in the spelling or punctuation of code that stops the computer reading it at all.
Example: A missing closing bracket or quotation mark.
Related: Error message, Logic error
Learn more: Errors and debugging
A request from a program to the kernel to do something it is not allowed to do itself, such as read a file.
Example: A text editor makes a system call to ask the kernel to write your document to the disk.
Related: Kernel, User space
Learn more: Hardware, operating system and applications as layers, Memory, storage and processes working together
The Ubuntu tool that lists running programs, draws graphs of processor, memory and network use and lets you end a program.
Example: Open it, click Resources to see the memory graph, or Processes to end a stuck program.
Related: Task Manager
Learn more: Slow computers, frozen apps, full storage and crashes, Resource monitoring, startup applications and when to seek repair
The part of most modern Linux systems, including Ubuntu, that starts services and keeps track of them.
Example: `systemctl status ssh` asks systemd whether the ssh service is running.
Learn more: Services, logs, storage and backups for administrators
Pressing the Tab key in the terminal to finish a file or command name for you.
Example: Typing Doc and pressing Tab completes it to Documents.
Related: Command history, File path
Learn more: Paths, case sensitivity, quoting, history and tab completion
A grid of rows and columns inside a document used to arrange information.
Example: A timetable in a school newsletter is a table.
Related: Spreadsheet, Word processor
Learn more: Tables, images, checking, track changes and exporting to PDF
The Windows tool that lists running programs, shows how busy the computer is and lets you end a stuck program.
Example: Press Ctrl+Shift+Esc to open it and sort programs by memory use.
Related: System Monitor, Frozen application
Learn more: Slow computers, frozen apps, full storage and crashes, Resource monitoring, startup applications and when to seek repair
The bar along the screen edge in Windows that shows open apps and shortcuts.
Example: Click an app icon on the taskbar to bring that window to the front.
Related: Start menu, Virtual desktop
Learn more: A tour of the Windows 11 desktop
A set of rules that makes sure data sent across a network arrives complete and in the right order.
Example: Web pages and email use TCP so that no part of the message goes missing.
Learn more: Packets, protocols, bandwidth and latency
A scam that claims your computer has a fault and asks for remote access or payment to fix it.
Example: A pop-up told Joseph to phone a number to remove a virus.
Learn more: Common scams: jobs, investments, impersonation and romance
A file a program makes for short-term use that is usually safe to remove once the program is finished.
Example: A half-finished download or a cache left behind after you install an update.
Related: Frozen application
Learn more: Slow computers, frozen apps, full storage and crashes, A safe maintenance routine
A window where you control the computer by typing text commands.
Example: Opening Terminal on Ubuntu and typing pwd shows which folder you are in.
Related: Shell, Command line
Learn more: Reading error messages and gathering evidence
A ready-made set of colours, fonts and backgrounds that gives a whole presentation one look.
Example: Choosing a blue theme changes every slide at once.
Related: Slide layout, Slide
Learn more: Building slides: layouts, themes and content
When a processor deliberately slows itself down to avoid getting too hot.
Example: A laptop on a soft bed blocks its vents, gets hot and becomes slow and sluggish.
Related: Heatsink, Cooling fan, CPU
Learn more: Power, cooling and the display
Something or someone that could cause harm to you or your data.
Example: A scammer sending fake emails is a threat; so is a flood or a stolen laptop.
Related: Vulnerability, Risk
Learn more: Threats, vulnerabilities, risks and malware
A short written analysis of what you protect, what could go wrong and what you will do about it.
Example: A shop lists its till records and customer phone numbers, then the ways each could be lost or stolen.
Related: Asset, Vulnerability
Learn more: Threat modelling and secure configuration
A written record of one problem, what was tried and how it ended.
Example: Ticket 214: printer offline, restarted the printer, reconnected it to Wi-Fi, solved.
Related: Help desk
Learn more: Next steps: IT support, networking and Linux administration
A region of the world that keeps the same clock time, so the same moment shows different hours in different places.
Example: When it is 09:00 in London in winter, it is 12:00 in Nairobi.
Related: Internet
Learn more: Display scaling, language, keyboard layout, date and time
The technology that scrambles data between your device and a website so others cannot read it.
Example: The padlock in the browser means the connection uses TLS.
Related: HTTPS, Encryption
Learn more: HTTPS and spotting suspicious websites
The last part of a domain name, such as .com, .org or .ke.
Example: In example.org the top-level domain is .org.
Related: Domain name, Subdomain
Learn more: Domains, URLs, HTTP and HTTPS
The shape formed by the devices and links of a network.
Example: A home network is usually a star, with every device joined to the router in the middle.
Learn more: What is a network?
The flat, touch-sensitive panel below a laptop keyboard that you use instead of a mouse.
Example: Slide one finger across it to move the pointer, and tap to click.
Related: Pointer, Gesture, Input device
Learn more: Mouse and touchpad skills
A tool that lists the routers a packet passes through on its way to a destination.
Example: traceroute example.org shows each hop and how long it took.
Learn more: Ports, TCP and UDP, ping and traceroute, Network settings and diagnostic tools
A feature that records every edit in a document so others can accept or reject each one.
Example: A teacher's corrections appear in colour, and you choose to accept or reject each.
Related: Spellcheck, Word processor
Learn more: Tables, images, checking, track changes and exporting to PDF
Following what you do online, often with cookies or similar tools, to build a profile.
Example: An advert for shoes followed Kamau from site to site because of tracking.
Related: Cookie, Digital footprint
Learn more: Personal information and your digital footprint
The collection of examples a machine learning model learns its patterns from.
Example: Thousands of photos each labelled cat or not cat.
Related: Machine learning, Model (AI)
Learn more: What AI is and how it learns
A holding place for deleted files, from which you can restore them until you empty it.
Example: Brian deletes a photo by mistake, opens the Recycle Bin and restores it.
Learn more: Ubuntu Files and your Home folder
Malware disguised as something useful or harmless so that you install it yourself.
Example: A free video player download that also installs a hidden program that steals passwords.
Learn more: Threats, vulnerabilities, risks and malware
Finding out step by step what is wrong with a problem and how to fix it.
Example: When the Wi-Fi fails, Amina checks other devices, then restarts the router.
Related: Hypothesis, Bug
Learn more: The eight-step troubleshooting method
A JavaScript structure that tries some code and, if it fails, runs a different block instead of crashing.
Example: try { parse(text) } catch (error) { show a friendly message }
Learn more: Validation, error handling and browser developer tools
A fast set of network rules that sends data without checking that every piece arrives.
Example: Video calls often use UDP, because a lost fraction of a second matters less than delay.
Learn more: Packets, protocols, bandwidth and latency
The modern kind of firmware on a computer's motherboard that starts the hardware and then hands over to the operating system.
Older computers used BIOS, and many people still say BIOS for both.
Example: Pressing a key such as F2 or Delete during start-up can open the UEFI settings screen on many laptops.
Related: Firmware, Boot, Bootloader
Learn more: What happens when a computer starts
To ask the system to remove an application's program and files properly, not just its shortcut.
Example: Choosing Uninstall in Settings, Apps, Installed apps on Windows.
Related: Application, Installer
Learn more: Applications: installing, updating and removing
A new version of software that fixes faults, closes security holes or adds features.
Example: Your phone offers an update that repairs a security problem.
Related: Operating system update, Windows Update
Learn more: The eight-step troubleshooting method
A written rule for when and how a computer is updated, and who checks that it worked.
Example: Security updates install automatically each night, and the administrator reviews the update log every Friday.
Related: Update, Administrator
Learn more: Managing users, updates and permissions
The full address of a web page, typed in the browser's address bar.
Example: https://www.example.com/news is the URL of one page on a website.
Related: Domain name, HTTPS
Learn more: Trusted sources, fake installers and bundled software
A common kind of socket and cable for connecting devices such as drives, keyboards and phones.
Example: You plug a flash drive into the USB port to copy files.
Learn more: Ports, cables and peripherals
A small oval USB plug that fits either way up and can carry data, video and power.
Example: One USB-C cable can charge a new laptop and connect it to a monitor.
Learn more: Ports, cables and peripherals
Your personal sign-in on a computer, with its own files and settings.
Example: Each person in the family has their own user account with a separate desktop.
Related: Login, Administrator
Learn more: What happens when a computer starts
A named collection of user accounts that can be given the same permissions together.
Example: Putting three staff accounts in one group lets them all use the shared printer.
Related: Permission, User account
Learn more: Users, groups and permissions in depth
The part of a computer's running software where ordinary programs live, with limited power over the hardware.
Example: Your browser and word processor run in user space and must ask the kernel to use the disk.
Learn more: Hardware, operating system and applications as layers
A named box in a program that holds a value which can change.
Example: A variable called score might hold 0 at the start and 10 later.
Learn more: Variables, data types, conditions, loops and functions
Software that records the history of a set of files, so you can see changes, compare them and go back to an earlier state.
Example: Using Git to save a snapshot of a website project with a short message after each change.
Related: Git, Naming convention
Learn more: File naming, document organisation and version control concepts
A record of earlier states of a file, so that you can go back to an older one.
Example: Joseph saved over his essay by mistake and used version history to open the copy from last Tuesday.
Learn more: Why backups matter and the ways data is lost, Making a backup plan and testing a restore
A video meeting is a live conversation over the internet in which people see and hear one another through cameras and microphones.
Example: Amina joins a video meeting from a link, switches off her microphone and listens until it is her turn.
Related: calendar invitation, shared link, Internet
Learn more: Shared documents, online meetings and calendars
An extra empty desktop you can switch to, to keep groups of open windows apart.
Example: Keep your email on one virtual desktop and a document on another.
Learn more: A tour of the Windows 11 desktop
A pretend computer, run as a program on a real computer, with its own system and files.
Example: A cloud provider running many customers' virtual machines on one physical server.
Related: Server, Cloud computing
Learn more: Local vs cloud computing
A way for the operating system to give each program its own tidy view of memory, and to use disk space when RAM runs short.
Example: When RAM is full, Ubuntu may move rarely used data to swap space on the disk, so programs keep running more slowly.
Related: RAM, Swap space
Learn more: Memory, storage and processes working together
Malware that attaches itself to files and copies itself from one file or device to another.
Example: An infected flash drive can pass a virus to every computer it is plugged into.
Learn more: Threats, vulnerabilities, risks and malware
Phishing done by phone call, where the caller pretends to be someone trustworthy.
Example: A caller claiming to be from the bank asked Fatuma for the code that had just been texted to her.
Learn more: Threats, vulnerabilities, risks and malware
A service that sends your internet traffic through a protected tunnel to a server elsewhere.
Example: Using a VPN on public Wi-Fi hides your traffic from other people on the same network.
Related: Encryption, Wi-Fi
Learn more: App permissions, public Wi-Fi and shared devices
A weakness that a threat can use to cause harm.
Example: An old, unpatched programme is a vulnerability; so is a password used on ten sites.
Learn more: Threats, vulnerabilities, risks and malware
A network that covers a large area by joining many smaller networks, such as the internet.
Example: A company links its offices in different towns over a WAN.
Learn more: What is a network?
A program you use inside a web browser, so it works on any computer with a browser and an internet connection.
Example: Writing a document in an online word processor instead of installing software.
Related: Browser, Application
Learn more: File systems and software compatibility
A server that stores websites and sends pages to browsers that ask for them.
Example: Typing a news site's address asks its web server to send you the front page.
Learn more: How a web browser works for you
Webmail is email that you read and send in a web browser, with your messages kept on the provider's servers.
The alternative is an email program on your computer, which downloads or syncs messages. Webmail works on any device with a browser and your login.
Example: Fatuma opens her mail by signing in to her provider's website.
Related: inbox, Browser, Cloud storage
Learn more: Email basics: addresses, inbox, To, CC and BCC
A way of joining a network and the internet by radio instead of a cable.
Example: Your phone joins the home Wi-Fi so it can use the internet without a cable.
Learn more: Ubuntu Settings: network, Bluetooth, display, sound and printers
Small panels in Windows that show quick information such as weather and news.
Example: Opening the Widgets panel shows today's weather in your town.
Related: Taskbar, Start menu
Learn more: A tour of the Windows 11 desktop
A special character such as * that stands for any characters in a file name.
Example: ls *.txt lists every file whose name ends in .txt.
Related: grep
Learn more: Reading and searching: file, cat, less, head, tail, grep and find
A rectangle on the screen that holds one app or one folder.
Example: A web browser window that you can move, resize, minimise or close.
Learn more: What happens when a computer starts
The Windows app where you change how the computer looks and behaves.
Example: Open Settings to change the screen brightness or connect to Wi-Fi.
Related: Start menu, Windows Update
Learn more: File Explorer and Windows Settings
A Windows app that gives you one window for command tools such as PowerShell and Command Prompt.
Example: Open Windows Terminal and use tabs to run PowerShell in one and Command Prompt in another.
Related: PowerShell, Command Prompt
Learn more: Command Prompt and PowerShell
The part of Windows that downloads and installs fixes and improvements.
Example: Windows Update installs a security fix overnight and asks you to restart.
Related: Update, Operating system update
Learn more: Microsoft Store, Windows Update and Windows Security
Microsoft's typed-command tool for finding, installing and updating apps on Windows.
Example: Typing winget upgrade in PowerShell lists apps that have newer versions.
Related: Package manager, Command line
Learn more: Applications: installing, updating and removing
A program for writing and formatting documents such as letters and reports.
Example: LibreOffice Writer and Microsoft Word are word processors.
Related: LibreOffice, Font
Learn more: Writing your first document in LibreOffice Writer
A workbook is one spreadsheet file, which can hold several worksheets.
In Excel the file is called a workbook. In LibreOffice Calc it is called a spreadsheet document. It is saved as .xlsx or .ods.
Example: A file called budget-march.ods with one sheet for rent and bills and another for savings.
Related: worksheet, Spreadsheet, cell
Learn more: Spreadsheet basics: cells, rows, columns and data types
The folder the terminal is currently 'in', which commands use unless you give another path.
Example: After cd ~/practice, the working directory is the practice folder; pwd prints its path.
Related: Home directory
Learn more: Finding your way: pwd, ls and cd
A worksheet is one grid of rows and columns inside a workbook.
Worksheets are shown as tabs at the bottom of the window, named Sheet1, Sheet2 and so on. You can rename them, add more and move between them.
Example: A workbook with the tabs January, February and March, each holding one month of a budget.
Related: workbook, Spreadsheet, cell
Learn more: Spreadsheet basics: cells, rows, columns and data types
One of several separate screens on Ubuntu for keeping groups of open windows apart.
Example: Keep your browser in one workspace and your documents in another.
Related: Virtual desktop, Dock
Learn more: A tour of the Ubuntu desktop
Malware that copies itself from one computer to another without anyone opening it.
Example: A worm spread through a school network by using a flaw that had not been updated.
Learn more: Threats, vulnerabilities, risks and malware
A common file type that bundles files together and makes them smaller.
Example: Zipping a folder of photos makes one smaller file that is easy to email.
Related: Archive, Compression
Learn more: ZIP files: compressing and extracting
Tricking people, rather than computers, into giving away secrets or access.
Example: A caller pretends to be from your bank and asks for the code just sent to your phone.
Related: Phishing, Multifactor authentication (MFA)
Learn more: Spam, phishing, password recovery and email account security