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.


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