Bartok is an optimizing compiler and managed runtime system for Common Intermediate Language (which .NET languages compile to), being developed by Microsoft Research. It aims to be efficient enough to be usable for writing operating systems. It provides services such as automatic memory management and garbage collection, threading, and marshalling data to and from native code, as well as verification of CIL code. Bartok is written in C#, including the garbage collector. Bartok is being used by Microsoft Research for the implementation of Singularity, a highly-dependable operating system written almost entirely in managed code.