You've been working with data that disappears when your program ends. I'll show you how to save data permanently using files, think configuration files, logs, and user data that persists between runs.
C++ gives you fstream, a library for reading and writing files like you use cin and cout for console I/O. You'll open files, read their contents, write new data, and handle errors when files don't exist.
By the end, you'll build programs that load settings from config files, process large text datasets, and create logs that survive crashes. Files turn temporary programs into tools that remember.