Operating systems and the command line

The operating system (OS) is the software that runs the computer. It manages the hardware from step 1, runs your programs, controls who can access what, and gives you a way to interact with all of it.

The big three

Windows runs on most business computers. If you work in IT, especially supporting offices, you’ll spend most of your time here. Two versions matter:

• Windows 11 is the current version.
• Windows 10 reached end of support on October 14, 2025. It still runs, but it no longer gets regular security updates, so computers still on it should be upgraded or replaced.
• Business computers usually run the Pro edition, which adds features like joining a company domain and BitLocker drive encryption.

macOS runs on Apple computers. It’s common at home and in creative work, and it’s built on a Unix foundation, which makes it a cousin of Linux.

Linux isn’t one product but a family of free operating systems, called distributions, such as Ubuntu, Debian and Fedora. Linux runs most of the internet: web servers, cloud platforms, firewalls and countless other devices. Even if you never use it as a desktop, you’ll eventually run into it.

Things every operating system does

• Users and permissions: who can sign in, and what each person can open, change or install. Most security problems come down to someone (or some program) having more access than it needed.
• Updates: fixing security holes and bugs. Keeping them current is one of the most important parts of the job.
• Processes and services: running programs, plus background programs (called services on Windows and daemons on Linux) that start automatically.
• File systems: how files are organized and stored. Windows uses drive letters (C:, D:). macOS and Linux use one tree starting at /.

The command line

The command line is a text window where you type commands instead of clicking. It looks old-fashioned, but there are good reasons IT people use it all the time:

• It’s faster for many tasks once you know a few commands.
• It works over remote connections where there’s no point-and-click screen.
• It can be automated, which is the subject of step 8.
• It shows you information the settings screens hide.

On Windows you’ll use PowerShell (search for it in the Start menu). On macOS and Linux it’s the Terminal, usually running a shell called bash or zsh.

Ten commands worth knowing

What you want	Windows (PowerShell)	macOS / Linux
Where am I?	Get-Location (or pwd)	pwd
List files	Get-ChildItem (or dir)	ls -l
Change folder	cd Documents	cd Documents
Show network settings	ipconfig /all	ip addr (Linux), ifconfig (macOS)
Test a connection	ping 8.8.8.8	ping 8.8.8.8
Look up a name	nslookup example.com	nslookup example.com
See running programs	Get-Process	ps aux
Stop a program	Stop-Process -Name notepad	kill with the process number
Get help on a command	Get-Help Get-Process	man ls
Restart the computer	Restart-Computer	sudo reboot

On Linux and macOS, sudo runs a command as an administrator and asks for your password. Treat it with respect: it lets you do anything, including break things.

Try this

Open PowerShell or Terminal and run:

ipconfig /all

(or ip addr on Linux). Find your computer’s IPv4 address and its default gateway. Don’t worry yet about what they mean. They’re the stars of step 3, and you’ll recognize them when you get there.

Key takeaways

• Windows dominates offices, Linux runs the internet, and macOS is common at home and in creative work.
• Updates and permissions are where most security is won or lost.
• Windows 10 is out of support as of October 2025.
• The command line is just another way to give instructions, and a handful of commands goes a long way.