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Terminal and commands

How can I ask a computer to do one observable action?

Terminal, shell, command, current directory and the first safe filesystem observations.

Last verified
2026-09-21
Review interval
365 days
Status
In review

01 / Overview

How can I ask a computer to do one observable action?

A terminal displays text input and output. A shell reads a command and asks the operating system to perform work. You begin by observing the current directory, listing names and creating a harmless file in the deterministic simulator.

Level
Intermediate
Units
2
Estimated time
40 min
What you will learn
  • Distinguish the terminal, shell and command.
  • Use observation before modification.
Know first
  • Computer
  • File
  • Folder
  • Process
Learning materials
  • Labs: available
  • Embedded practice: available
  1. 01Terminal, shell and command20 min
  2. 02Navigate and change virtual state20 min
Start topic →

02 / Learn

Learn

  1. Terminal, shell and command

    Distinguish the window, the command interpreter and the instruction you type.

    Open lesson →
  2. Navigate and change virtual state

    Use the current directory, paths and small reversible changes inside the safe simulator.

    Open lesson →

03 / Concepts

Concepts

Three different layersterminal-shell-command
The terminal displays, the shell interprets and the command requests one action.
Current directorycurrent-directory
The starting location used to resolve a relative path.

04 / Commands

Commands

EnvironmentCommandPurposeLab
linuxpwdPrint the current directory.Available in Command Lab
linuxlsList names in the current directory.Available in Command Lab
multimkdir labCreate a directory in virtual state.Available in Command Lab
linuxtouch note.txtCreate an empty simulated file.Available in Command Lab

05 / Labs

Labs

  1. Command Lab

    Deterministic browser simulator for CMD, Linux shell and PowerShell practice with virtual state.

    deterministic simulator
    Open safe simulator →

07 / Security

Security

  1. A copied command is untrusted input: inspect the command, options, arguments, location and expected effect before running it.

08 / Troubleshooting

Troubleshooting

  1. If a path fails, first print the current directory and list its names; do not change permissions as a first guess.

09 / Quick checks

Quick checks

  1. Which layer reads the command: terminal, shell or file?

10 / GRAPH

Used in certifications

These links reuse canonical knowledge; the certification page does not own or duplicate the topic.

    12 / Sources and freshness

    Sources and freshness

    Last verified
    2026-09-21
    Review interval
    365 days
    Source version
    GNU Bash manual · Microsoft PowerShell overview · Command Lab grammar v1