ly for combating malware , because the usual malware cannot run on DOS systems. The DOS enables virus scanners to be started and simple file processing. The same applies to recovery CDs from image programs.
OS / 2 , the operating system developed by IBM and Microsoft from 1987 onwards, was no longer based on DOS, although there are certain peculiarities of the DOS system. The downward compatibility required at that time was ensured via the DOS emulation kernel , also known as multithreading (Multiple Virtual DOS Machine , MVDM) . This technology, which was revolutionary at the time, has also turned out to be a major weak point, because the DOS mode only ran exclusively on the screen and all drivers had to take part in the switchover to DOS mode. Later 32-bit versions from 1991 onwards allowed DOS multitasking sessions with their own window manager ( Workplace Shell , Presentation Manager ). Even more modern Windows such as Windows NT , Windows 2000 , Windows XP , Windows Vista and all newer versions are based on the kernel of the 32.bit operating system Windows NT 3.1, introduced in 1991, which was completely redeveloped at the time and has no "DOS roots": MS-DOS / PC DOS is neither a component nor the technical basis of these operating systems, although the Win32 subsystem of modern 32-bit Windows versions still simulates the functionality of MS-DOS. More modern OS / 2 versions followed the same path: The DOS box ( command line ) runs in these systems as an interpreter ( cmd.exe , COMMAND.COM), which emulates DOS in order to execute programs written in DOS. The function is that of a scripting language . The 64-bit versions of Windows XP and later no longer have the ability to run MS-DOS programs.
Today there are DOS emulators such as DOSBox , which runs on different operating systems, and the Linux program DOSEMU . Instead, however, entire PC emulators (see also virtualization ) can be used that attempt to reproduce the hardware of a computer true to the original. An original DOS can be installed and used on such 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.