Users and permissions
🏠The everyday picture
In an office building, everyone has an ID card, but not every card opens every door. Visitors get the lobby. Staff get their floor. Only the manager's card opens the safe. This protects people from mistakes as much as from thieves.
📘What it really is
- Every person (and many programs) uses the computer as a user account.
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Permissions decide what each user may do with each file or folder: read (open it), write (change it) and execute (run it as a program).
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An administrator (on Linux and Mac, the root user) can change anything, including the OS itself. That's powerful and dangerous: a mistake or a virus running as administrator can damage everything.
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That's why the OS asks "Do you want to allow this app to make changes?" or asks for your password before installing software. It's checking that you really mean to use administrator power.
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The rule professionals follow is least privilege: give each person and program only the access it needs, nothing more. You'll meet this rule again in security (Level 6) and in AI tools (Level 7).
🖱️Try it
Look at your user accounts (Windows: Settings → Accounts; Mac: System Settings → Users & Groups). Is your everyday account an administrator? Many security experts recommend a separate, standard account for everyday use.
✅Quick check
*An AI coding tool asks for permission to delete files anywhere on your computer. What's the least-privilege
Show the answer
answer?* Allow it only inside your project folder, and only as much as the task needs. Never give it the whole computer.
Why does installing software ask for an administrator password, but opening a document doesn't?
Show the answer
Installing changes the system for everyone; opening a document only reads your own file.