> For the complete documentation index, see [llms.txt](https://docs.virtual-flow.org/documentation-vf1/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.virtual-flow.org/documentation-vf1/vfvs/principles-and-theory.md).

# Background  and Principles

- [Directory Structure](https://docs.virtual-flow.org/documentation-vf1/vfvs/principles-and-theory/directory-structure.md)
- [Input & Output Databases](https://docs.virtual-flow.org/documentation-vf1/vfvs/principles-and-theory/input-and-output-databases.md)