TempleOS

TempleOS is an open-source and free operating system written by Terry A. Davis between 2005 and 2017. It is designed for AMD64 and IA-64 architectures only. TempleOS runs only on 640x480 resolution and 16-color display.

Advantages

 * TempleOS comes with shell and mouse support.
 * TempleOS has many games and applications. Such as EagleDive and Psalmody.

Disadvantages

 * TempleOS has no support for Network and sound (only PC Speaker).
 * TempleOS commands are not easy for beginners.