DexOS is an acronym, Dex is short for DOS Extreme. It is a free operating system (OS) for 32-bit x86 computers; a port to the ARM processor (to run on the GP2X) is underway. It is written in pure assembly language using FASM: the flat assembler. It is a V2_OS fork.
DexOS is designed as a modern DOS. It runs in protected mode, is single-tasking (one process), has a command line interface and a graphical user interface, can load modules such as sound drivers, and has some built in commands, such as TIME, DATE, MORE (text viewer), HELP, and RUN. To run programs, it is optional to use RUN and the .dex extension. It has some network abilities, such as running a HTTP server.
Development is led by Craig Bamford and members of the DexOS community.