Microsoft originally developed the
DOS Protected Mode Interface (
DPMI) for
Windows 3.0,
and later gave the standard to the DPMI
Committee.
DPMI is used as an infrastructure for running 32 bit programs
under DOS, and to allow old DOS programs to run in a protected
environment which makes it possible to use more RAM than the 1MB
that is normally addressable in 20-bit real mode.
The DPMI environment limits the interrupts and BIOS calls that a
program can perform, plus adding new interrupt calls such as int 31,
that programs can use to modify descriptor tables, allocate and
free memory, and executing real mode code. Programs that run in DPMI
can be 32 bit and use the flat 32-bit model. It is possible using
DPMI to run independent virtual machines on one PC, for
multi-tasking.
references:
http://www.tenberry.com/web/dpmi/toc.htm
http://www.whatis.com/definition/0,,sid9_gci213913,00.html