Quick reference

Look-up tables for when you know what you are doing and just need to be reminded. New to something? Read the lesson first: every command here is explained in a lesson before you run it.

Keyboard shortcuts

A shortcut is a combination of keys that does a job faster than the mouse. Hold the first key, press the second, then let go of both. On Ubuntu the Super key is the one with the Windows logo. Most everyday shortcuts are the same on both systems.

What it does	Ubuntu (GNOME)	Windows 11
Copy the selected item	Ctrl + C	Ctrl + C
Cut the selected item	Ctrl + X	Ctrl + X
Paste	Ctrl + V	Ctrl + V
Undo the last action	Ctrl + Z	Ctrl + Z
Redo	Ctrl + Shift + Z (or Ctrl + Y in some apps)	Ctrl + Y
Select everything	Ctrl + A	Ctrl + A
Save	Ctrl + S	Ctrl + S
Find in a page or document	Ctrl + F	Ctrl + F
Print	Ctrl + P	Ctrl + P
Switch between open windows	Alt + Tab	Alt + Tab
Close the current window	Alt + F4 (or Ctrl + W in many apps)	Alt + F4
Open the Activities overview / Start menu	Super	Windows key
Take a screenshot	Print Screen	Windows key + Shift + S
Lock the screen	Super + L	Windows key + L
Open the file manager	Super, then type Files	Windows key + E
Open a terminal	Ctrl + Alt + T	Windows key, then type Terminal
New browser tab	Ctrl + T	Ctrl + T
Close a browser tab	Ctrl + W	Ctrl + W
Reload a web page	Ctrl + R or F5	Ctrl + R or F5
Rename a selected file	F2	F2

Common file extensions

A file extension is the short ending after the last dot in a file name. It hints at what kind of file it is and which program usually opens it. Windows may hide extensions by default; Ubuntu shows them in Files.

⛔ Be carefulProgramme files such as .exe, .msi and .sh can change your computer. Do not open one that arrived by email or from a site you do not know.

Extension	Kind of file	Usually opened with
.txt	Plain text with no formatting	Text Editor (Ubuntu), Notepad (Windows)
.docx	Word-processor document	LibreOffice Writer, Microsoft Word
.odt	Open-format word-processor document	LibreOffice Writer
.xlsx	Spreadsheet	LibreOffice Calc, Microsoft Excel
.ods	Open-format spreadsheet	LibreOffice Calc
.pptx	Presentation slides	LibreOffice Impress, Microsoft PowerPoint
.pdf	Fixed-layout document for reading and sharing	A web browser or a PDF viewer
.jpg / .jpeg	Photograph (compressed image)	Any image viewer or browser
.png	Image with sharp edges, can be transparent	Any image viewer or browser
.mp3	Compressed audio	Any music or media player
.mp4	Video	Any video player or browser
.zip	Compressed bundle of files (archive)	Built-in archive tools on both systems
.html	Web page	A web browser
.py	Python programme	Python, or any text editor to read it
.sh	Linux shell script (a list of commands)	A terminal on Ubuntu. Check what it does before running it.
.deb	Ubuntu installer package	App Center or apt on Ubuntu
.exe / .msi	Windows programme or installer	Windows. Run only files from sources you trust.

Ubuntu terminal commands

You type these in the Terminal and press Enter. Names are case-sensitive. Try them first in a practice folder such as ~/practice, where nothing important can be lost. The tilde (~) means your home folder.

⛔ Be carefulrm deletes immediately with no undo, so check the name before pressing Enter. Never use rm -rf on a real folder. sudo can change or break the whole system. Only use it for commands from a lesson or from official Ubuntu documentation, and never paste in a command you do not understand.

Command	What it does	Example
pwd	Shows which folder you are in (print working directory)	pwd
ls	Lists the files and folders here	ls -l
cd	Moves into another folder	cd ~/practice
mkdir	Makes a new folder	mkdir notes
touch	Makes an empty file, or updates its time stamp	touch hello.txt
cp	Copies a file	cp hello.txt copy.txt
mv	Moves or renames a file	mv copy.txt renamed.txt
cat	Shows the contents of a text file	cat hello.txt
less	Reads a long file one screen at a time (press q to quit)	less hello.txt
man	Opens the manual page for a command (press q to quit)	man ls
clear	Clears the terminal screen	clear
echo	Prints text on screen	echo Hello
rm	WARNING: deletes a file for good. It does not go to the Bin.	rm ~/practice/old.txt
rmdir	Removes an empty folder	rmdir ~/practice/notes
sudo	WARNING: runs the next command with administrator power	sudo apt update
apt	Installs and updates software (usually with sudo)	sudo apt install vlc
ping	Checks whether another computer replies (Ctrl + C stops it)	ping -c 4 example.com
ip addr	Shows your network addresses	ip addr

Windows terminal commands

These work in Terminal on Windows 11. Most run in both PowerShell and Command Prompt (cmd). The ones marked PowerShell only will not work in cmd. Practise in a folder such as C:\Users\<name>\practice.

⛔ Be carefuldel and format cannot be undone. del skips the Recycle Bin, and format wipes everything on a drive. Only use them in a practice folder, and never run format at all while learning. Open Terminal as administrator only when a trusted guide tells you to.

Command	What it does	Example
cd	Moves into another folder	cd $HOME\practice
dir	Lists files and folders (cmd and PowerShell)	dir
Get-Location	Shows which folder you are in (PowerShell only; in cmd just type cd)	Get-Location
mkdir	Makes a new folder	mkdir notes
copy	Copies a file	copy hello.txt copy.txt
move	Moves a file	move copy.txt notes\copy.txt
ren	Renames a file	ren copy.txt renamed.txt
type	Shows the contents of a text file	type hello.txt
cls	Clears the screen	cls
echo	Prints text on screen	echo Hello
help	Lists commands, or explains one	help dir
del	WARNING: deletes a file for good. It skips the Recycle Bin.	del practice\old.txt
rmdir	Removes an empty folder	rmdir notes
format	WARNING: erases an entire drive	Do not run it. Use Settings to manage drives.
ipconfig	Shows your network addresses	ipconfig
ping	Checks whether another computer replies	ping example.com
tasklist	Lists running programmes	tasklist

Networking terms

These words appear in Wi-Fi settings and in error messages. Knowing them helps you describe a problem clearly.

Term	Plain meaning	Example or where you see it
IP address	The number that identifies a device on a network	192.168.1.20 on a home network
Router	The box that connects your home devices to the internet and to each other	The box from your internet provider
Modem	Turns the signal from your provider into data your router can use	Often built into the router
Wi-Fi	Wireless connection to your router	The network name (SSID) you pick from a list
SSID	The name of a Wi-Fi network	HomeNetwork-5G
Ethernet	Connection by network cable	A cable from laptop to router
DNS	Turns a name like example.com into an IP address	Websites fail to load but a ping to an IP address works
DHCP	Hands out IP addresses automatically	Your laptop gets an address when it joins Wi-Fi
Default gateway	The address of the router, the way out of your network	Often 192.168.1.1
MAC address	A fixed hardware ID of a network card	Shown in network details
Bandwidth	How much data can flow per second	Measured in Mbps
Latency	The delay before data starts to arrive	Shown in ms by ping
Firewall	A filter that blocks unwanted network traffic	Built into Ubuntu and Windows
VPN	An encrypted tunnel for your traffic through another server	Used on public Wi-Fi or for work
HTTPS	Web traffic that is encrypted	The padlock beside a web address

Quick troubleshooting

Start with the simplest fix and change only one thing at a time. Write down what you tried. If a step asks for administrator rights you do not understand, stop and ask for help.

Problem	Try this first	Ubuntu or Windows detail
The computer is frozen	Wait a minute, then try Alt + Tab or Esc. If nothing works, hold the power button to switch off, then start again.	Hard power-off can lose unsaved work, so save often.
A programme will not respond	Close it and open it again.	Ubuntu: Settings, Apps, or use System Monitor. Windows: Ctrl + Shift + Esc opens Task Manager, then End task.
No internet	Check Wi-Fi is on, then restart the router and the laptop.	Ubuntu: Wi-Fi icon in the top-right menu. Windows: Wi-Fi icon in the taskbar, or Settings, Network and internet.
One website will not load	Reload, then try another site to see if it is only that one.	Try a private window to rule out cookies and extensions.
No sound	Check the volume and the output device.	Ubuntu: Settings, Sound. Windows: Settings, System, Sound.
The screen is too dim or too bright	Use the brightness keys or setting.	Ubuntu: Settings, Power or Display. Windows: Settings, System, Display.
The laptop is very slow	Close unused programmes and browser tabs, then restart.	Check free storage space as well.
The disk is nearly full	Move large files to external storage and empty the Bin.	Ubuntu: Disk Usage Analyzer if installed. Windows: Settings, System, Storage.
USB drive not showing	Unplug it and plug it in again, try a different port.	Ubuntu: look in the Files sidebar. Windows: look in This PC.
Printer will not print	Check it is on, has paper and is selected in the print window.	Ubuntu: Settings, Printers. Windows: Settings, Bluetooth and devices, Printers and scanners.
Forgot a password	Use the official reset link or recovery option for that account.	Never share a password or recovery code with anyone.

Maintenance schedule

A few small habits keep a computer safe and quick. Put the weekly and monthly jobs in your calendar.

How often	Job	Why it matters
Every day	Save your work and shut down or sleep the laptop properly	Avoids lost files and file damage
Every week	Install updates	Updates fix security holes. Ubuntu: Software Updater. Windows: Settings, Windows Update.
Every week	Restart the computer	Finishes updates and clears out slow programmes
Every week	Back up important files	A backup is a spare copy if the laptop is lost or breaks
Every month	Check free storage space	A full disk makes a computer slow and can stop updates
Every month	Empty the Bin or Recycle Bin and clear the Downloads folder	Frees space. Check nothing needed is inside first.
Every month	Remove apps you no longer use	Fewer apps means fewer things to update and attack
Every month	Test that you can open a backup file	A backup you cannot open is no use
Every three months	Clean dust from vents and the keyboard (laptop off, unplugged)	Heat slows a laptop and shortens its life
Every year	Review passwords and account recovery details	Keeps accounts recoverable and secure

Security checklist

Tick these off one at a time. Each one lowers your risk of losing money, accounts or files. Never type your real password into practice exercises.

⛔ Be carefulNever turn off your antivirus or firewall because a website or caller tells you to. Real support staff will not ask for your password or recovery codes.

Do this	Why	How to check
Use a long, different password for each account	One leaked password cannot open your other accounts	Use a password manager or a passphrase of several random words
Turn on multifactor authentication	A thief needs more than your password	In each account's security settings
Keep recovery codes somewhere safe and offline	They get you back into an account if you lose your phone	Write them down and store them away from the computer
Install updates promptly	Updates close known holes	Ubuntu: Software Updater. Windows: Windows Update.
Keep the firewall on	It blocks unwanted connections	Ubuntu: ufw is available. Windows: Windows Security, Firewall and network protection.
Lock the screen when you step away	Stops others using your accounts	Ubuntu: Super + L. Windows: Windows key + L.
Check the web address before signing in	Fake sites copy real ones	Look for the correct domain name and the padlock (HTTPS)
Do not click links or open attachments you did not expect	This is how phishing and malware spread	Contact the sender another way to confirm
Install software only from trusted sources	Fake downloads often hide malware	Ubuntu: App Center. Windows: Microsoft Store or the maker's own site.
Back up your files regularly	Protects you from ransomware and hardware failure	Keep at least one copy off the laptop
Be careful on public Wi-Fi	Others on the same network may be able to watch weak connections	Use HTTPS sites only. Avoid banking, or use a VPN you trust.