4.28. DPMI - DOS Protected Mode Interface support unit
Targets: MS-DOS only
The DOS Protected Mode Interface
(DPMI) was defined to allow DOS programs to access the extended memory
of PC architecture computers while maintaining system protection.
DPMI defines a specific subset of DOS and BIOS calls that can be made
by protected mode DOS programs. It also defines a new interface
via software interrupt 31h that protected mode programs use to allocate memory,
modify descriptors, call real mode software, etc. Any operating system
that currently supports virtual DOS sessions should be capable of supporting
DPMI without affecting system security. Some DPMI implementations can execute
multiple protected mode programs in independent virtual machines.
Thus, DPMI applications can behave exactly like any other standard
DOS program and can, for example, run in the background or in a window
(if the environment supports these features). Programs that run in protected
mode also gain all the benefits of virtual memory and can run in 32-bit
flat model if desired.
The DPMI unit intended for simplification access to DPMI functions
from Pascal program.