The MenuetOS (or MeOS) operating system (OS) has a monolithic, preemptive, realtime kernel, including video drivers, for 32-bit and 64-bit x86 architecture computers. It has a graphic desktop, games, and networking (TCP/IP stack), yet fits on one 1.44MB floppy disk. Development focuses on being fast, simple, efficient. It is all written in FASM Assembly language, and facilitates easy, full-featured Assembly programming, in contrast to the common view that Assembly languages are usable mainly for old and embedded systems. MenuetOS was originally written for 32-bit x86 processors and released under the GPL, so many of its programs are licensed as GPL. The 64-bit MenuetOS, often called Menuet 64, remains a platform for learning 64-bit assembly language programming. Menuet 64 is distributed as freeware with no source code for core components. It works smoothly in QEMU which can emulate a 64-bit machine on a 32-bit machine. The author is Ville Mikael Turjanmaa.