Files and directories

Summary

A file is a named collection of data. A directory organizes names into a hierarchy, and a path describes how to reach a file or directory.

Introduction

Programs need stable names for information that must survive after a process exits. The OS presents files and directories so programs do not need to manage raw storage locations.

Explanation

A directory can contain file names and names of other directories. An absolute path begins from a root location; a relative path begins from the current working directory. Separators and root notation differ across operating systems, but the hierarchical idea is shared. Common operations include create, open, read, write, rename, and delete.

Real-world example

Follow the hierarchy

/home/lee/project/
├── app.js
└── notes/
  └── todo.txt

Code example

current directory: /home/lee/project
relative path:     notes/todo.txt
absolute path:     /home/lee/project/notes/todo.txt
parent directory:  ..

Common mistakes

• Assuming a file extension guarantees the file’s actual content.
• Confusing a relative path with a path that starts at the root.
• Believing deleting a directory name always securely erases every underlying byte immediately.

Quiz

Key takeaways

• Files hold named data; directories organize names hierarchically.
• Absolute paths start at a root; relative paths start at a current location.
• Paths provide logical names rather than exposing physical storage layout.