The File System Is a Single Tree

A new drive doesn't add another tree: it grows as one more branch

On Windows, you have multiple drives like C:\ and D:\, a "forest" of separate roots. But on Unix/Linux, everything grows from a single /. Even when you plug in a USB drive, it doesn't create a new drive letter. It appears as a branch on the tree, under /media on Linux or /Volumes on macOS.

Thanks to this "single tree" design, every file can be reached from /. If you ever get lost, pwd shows where you are, and cd / takes you to the top. It's a simple idea, but it's been working for over 50 years.

The simplest designs tend to last the longest. The root directory is a perfect example.