Introduction

The command line is a text-based way to control your computer by typing instructions into a terminal, where a shell reads each command and carries it out immediately.

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By the end of this lesson you'll know what the command line, shell, and terminal actually are, you'll be able to read a command prompt, and you'll have run your first four real commands — echo , pwd , whoami , and date .

Think of the graphical interface (the windows, icons, and buttons you click) as ordering from a menu with pictures — quick and friendly, but you can only pick what's on the menu. The command line is like talking directly to the chef: you can ask for anything, customise every detail, and repeat the exact same order a thousand times without lifting a finger. It looks bare because it's powerful — there are no pictures in the way, just you telling the computer precisely what to do.

1. What Is the Command Line?

The command line is a text-based way to control your computer . Instead of clicking buttons and dragging files, you type an instruction, press Enter, and the computer carries it out immediately. Three words get used for closely related things, and it's worth pinning them down once:

In casual conversation people mix these up constantly, and that's fine. The mental picture that matters: the shell (e.g. bash) runs inside the terminal window, and together they let you use the command line .

2. The Prompt — Where You Type

When you open a terminal, the shell shows a prompt — its way of saying "I'm ready, type something". It often ends in a dollar sign $ (or % on some Macs). The single most important rule for beginners: you don't type the prompt symbol . It's just the shell's marker for where your typing begins.

3. Why the Command Line Is So Powerful

If clicking is easier, why learn this? Because once a task can be typed , it can be repeated, combined, and automated — things a mouse can't do well.

4. Your First Command: echo

The friendliest place to start is echo , which simply prints text back to you. Wrap text in "double quotes" when it contains spaces or punctuation, so the shell treats it as one piece of text. Read this worked example, run it, and check your output matches.

Now you try. Fill in the blank marked ___ using the hint in the comment, then run it.

5. Where Am I & Who Am I? pwd , whoami , date

Three more safe, everyday commands answer questions about your current session. whoami prints your username, pwd (Print Working Directory) prints the folder you're currently "in", and date prints the system clock. None of them change anything — run them as often as you like.

Your turn again. One command is missing — fill in the ___ so the program prints your current folder and then your username.

Start typing a command or file name and press Tab — the shell finishes it for you (this is "tab completion"). Press Tab twice to see all the possibilities. It saves typing and prevents spelling mistakes, and it's one of the first habits that makes the terminal feel fast.

Run these to see the exact messages the shell gives back:

No blanks this time — just a brief and an outline to keep you on track. Use only the four commands you learned, run it, and check your output against the example in the comments.

Practice quiz

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