All data on a computer lives in files—the units you open, save, move, and share.
Directories (folders) organize those files into a tidy tree, from a single root down to many subfolders.
The OS keeps it all straight via a file system (e.g., NTFS, APFS, ext4), tracking names, locations, sizes, and dates.
In the previous post, we explored the concept of program installation. We learned that installing a program isn’t just copying files—it’s a process where the operating system recognizes and registers the program so it can be executed.
This time, let’s take a look at something even more fundamental in the world of computers: files and directories.
What Is a File?
All data handled by a computer is ultimately stored as a file—a container that holds information such as documents, photos, music, videos, or even programs themselves. A Word report, a photo from your phone, and an MP3 track are all files. It’s the everyday unit you open, close, move, and save.
Why We Need Directories (Folders)
Files alone aren’t enough. With thousands of files mixed together, finding anything would be painful. That’s where directories (a.k.a. folders) help: they’re boxes that organize files into meaningful groups so you can find what you need quickly.
The Tree Structure
Directories can contain other directories, forming a tree. At the top sits the root, with many branches beneath:
- Windows: Typically the C: drive as root, with folders like Program Files, Users, and Windows.
- Everyday organizing: e.g., a “My Pictures” folder with subfolders Travel, Family, and School to find images faster later.
How the OS Manages Files
The operating system tracks where files live, their names, sizes, and last-modified dates using a file system:
- Windows: NTFS
- macOS: APFS
- Linux: ext4
Names differ, but the goal is the same: to organize and manage data efficiently.
You Already Use This—Every Day
On your phone, the photo gallery’s albums and a music app’s playlists are the same idea: files grouped into folders. A file is the basic unit of data; a directory is the container that keeps things tidy.
Wrapping Up
- Everything on a computer is made of files.
- Directories organize those files into a searchable structure.
- The OS + file system manage names, locations, sizes, and dates behind the scenes.
Understanding files and directories is a foundational step that makes later concepts much easier to grasp.
In the next post, we’ll explore file extensions.
You can view the original Korean blog post at the link below