# (Optional) Lab4: File Systems

<mark style="color:red;background-color:red;">**Note: Lab 4 is not required for all the students**</mark><mark style="color:red;background-color:red;">.</mark>

**In the previous two assignments, you made extensive use of a file system without actually worrying about how it was implemented underneath.** For this last assignment, you will **improve the implementation of the file system**.

You will be working primarily in the `filesys/` directory.

**You may build project 4 on top of project 2 or project 3.**

* In either case, all of the functionality needed for project 2 must work in your filesys submission.
* If you build on project 3, then all of the project 3 functionality must work also, and you will need to edit `filesys/Make.vars` to **enable VM functionality**. You can receive up to 10% extra credit if you do enable VM.

**Here are the sections in this chapter:**

{% content-ref url="optional-lab4-file-systems/background" %}
[background](https://pkuflyingpig.gitbook.io/pintos/project-description/optional-lab4-file-systems/background)
{% endcontent-ref %}

{% content-ref url="optional-lab4-file-systems/suggestions" %}
[suggestions](https://pkuflyingpig.gitbook.io/pintos/project-description/optional-lab4-file-systems/suggestions)
{% endcontent-ref %}

{% content-ref url="optional-lab4-file-systems/your-tasks" %}
[your-tasks](https://pkuflyingpig.gitbook.io/pintos/project-description/optional-lab4-file-systems/your-tasks)
{% endcontent-ref %}

{% content-ref url="optional-lab4-file-systems/faq" %}
[faq](https://pkuflyingpig.gitbook.io/pintos/project-description/optional-lab4-file-systems/faq)
{% endcontent-ref %}