> For the complete documentation index, see [llms.txt](https://mr-poston-1.gitbook.io/c++/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mr-poston-1.gitbook.io/c++/3.-libraries/3.1-header-files/3.1.1-header-files.md).

# 3.1.1 Header Files

As you have seen in your programs thus far, importing libaries is a key part to each program. Libraries allow you to extend the functionality of C++.

The libraries you have used so far have been internal libraries. In this lesson you are going to look at the steps to create and use your own libraries.