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QEMU is free software written by Fabrice Bellard that implements a fast
processor [[emulator|emulation]], allowing a user to run one operating system
within another one.  It is similar to projects such as [[Bochs]] and VMware
Workstation, but has several features these lack, including increased speed and
support for multiple architectures.  By using dynamic translation it achieves a
reasonable speed while being easy to port on new host CPUs.

QEMU has two operating modes:

  * User mode emulation: QEMU can launch Linux processes compiled for one CPU
    on another CPU.  Linux [[system call]]s are converted because of endianness
    and 32/64 bit mismatches.  Wine and Dosemu are the main targets for QEMU.

  * System mode emulation: QEMU emulates a full system, including a processor
    and various peripherials.  It enables easier testing and debugging of
    system code.  It can also be used to provide virtual hosting of several
    virtual PCs on a single server.

The majority of the program is under the [[LGPL]], with the system mode
emulation under the [[GPL]].

# External Links

  * <http://www.nongnu.org/qemu/>
  * [Qemu on Windows](http://www.h7.dion.ne.jp/~qemu-win/)