<operating system> Any system offering the user the choice of
two operation systems (OSes) under which to start a
computer. A dual boot system allows the user to run programs
for both operating systems on a single computer (though not
simultaneously). The term "multiple boot" or "multiboot"
extends the idea to more than two OSes.
The OSes are generally unaware of each other's existence.
They are installed on separate hard disk partitions or on
separate disks. They may be able to access each other's
files, possibly via some extra driver software if they use
different file systems.
The OSes need not be completely different - they might be
different versions of Microsoft Windows (e.g. Windows XP
and Windows NT) or Linux (e.g. Debian and Fedora).
A dual boot system differs from an emulator such as
vmware, which runs one or more OSes "on top" of the primary
OS, using its resources.
