file system

A file system is how the operating system organizes everything on a disk into named files tucked inside folders — and how it finds any one of them again later. A bare disk is really just a vast sea of numbered blocks; the file system is the librarian on top, keeping the catalog that says 'the photo you call beach.jpg lives in these blocks, inside the Pictures folder.' Without it, your files would be there in the raw bits, but nothing could tell where one ends and the next begins.

You navigate it by path — a trail of folder names that pins down exactly where a file sits, like /Users/jo/notes/todo.txt or C:\Users\Jo\todo.txt. Read it left to right: start at the top, step down through each folder, and the last name is the file itself. That string is an address, and following it always lands you in one precise spot in the tree.

The folders nest into a tree, branching down from a single top called the root. This shape is why the same notes.txt can sit harmlessly in two different folders: their full paths differ, so the system never confuses them. The file system also remembers each file's size, its timestamps, and who's allowed to open it — the bookkeeping that turns raw storage into something you can actually browse.