h a “virtual computer”.
In contrast to virtual machines , special DOS emulators are generally more effective and therefore faster and more resource-saving , but also not fully compatible, since in particular direct system access such as various BIOS routines that are used outside of the DOS API, as well as direct access to the hardware , such as direct memory management, do not work. It is also possible that a PC emulator does not provide all the functions of the emulated hardware true to the original, so that one or the other DOS program works incorrectly or not at all. In addition, the speed advantage is lost if the host system supports Pacifica or Vanderpool technology, as these technologies accelerate virtual machines considerably, but have no effect on emulators. On such systems, virtual machines are usually faster than DOS emulators.