<s>
In	O
computing	O
,	O
the	O
Virtual	O
Control	O
Program	O
Interface	O
(	O
VCPI	O
)	O
is	O
a	O
specification	O
published	O
in	O
1989	O
by	O
Phar	O
Lap	O
Software	O
that	O
allows	O
a	O
DOS	B-Device
program	O
to	O
run	O
in	O
protected	B-Application
mode	I-Application
,	O
granting	O
access	O
to	O
many	O
features	O
of	O
the	O
processor	O
not	O
available	O
in	O
real	B-Application
mode	I-Application
.	O
</s>
<s>
It	O
was	O
supplanted	O
by	O
DOS	B-Device
Protected	B-Application
Mode	I-Application
Interface	O
(	O
DPMI	O
)	O
shortly	O
after	O
being	O
introduced	O
,	O
due	O
in	O
large	O
part	O
to	O
VCPI	O
's	O
inability	O
to	O
work	O
in	O
Windows	B-Application
3.0	I-Application
'	O
s	O
protected	B-Application
mode	I-Application
.	O
</s>
<s>
Architects	O
,	O
Lotus	O
Development	O
Corp.	O
,	O
Quadram	O
,	O
Qualitas	O
and	O
Rational	O
Systems	O
,	O
VCPI	O
is	O
provided	O
by	O
an	O
expanded	B-Device
memory	I-Device
manager	O
in	O
DOS	B-Device
(	O
e.g.	O
</s>
<s>
CEMM	B-Device
,	O
QEMM	B-Device
,	O
later	O
EMM386	B-Device
)	O
and	O
does	O
allow	O
80386	O
protected-mode	B-Application
DOS	B-Device
extenders	I-Device
to	O
coexist	O
with	O
80386	O
EMS	O
expanded	B-Device
memory	I-Device
emulators	O
.	O
</s>
<s>
It	O
was	O
eclipsed	O
by	O
DPMI	O
,	O
most	O
notably	O
because	O
it	O
was	O
not	O
supported	O
for	O
DOS	B-Device
programs	O
run	O
in	O
Windows	B-Application
3.0	I-Application
'	O
s	O
native	O
protected	B-Application
mode	I-Application
(	O
called	O
386	O
enhanced	O
mode	O
)	O
and	O
because	O
VCPI	O
runs	O
programs	O
in	O
Ring	B-Operating_System
0	I-Operating_System
,	O
which	O
defeated	O
the	O
purpose	O
of	O
x86	O
protection	O
.	O
</s>
<s>
It	O
also	O
did	O
not	O
work	O
with	O
OS/2	B-Application
2.0	O
and	O
later	O
.	O
</s>
<s>
VCPI	O
was	O
only	O
supported	O
in	O
Windows	B-Application
3.0	I-Application
real	B-Application
mode	I-Application
,	O
some	O
programs	O
could	O
run	O
in	O
Windows	O
3.x	O
standard	O
mode	O
.	O
</s>
<s>
Earlier	O
Windows/386	O
2.1	O
was	O
not	O
compatible	O
with	O
DOS	B-Device
extenders	I-Device
at	O
all	O
.	O
</s>
<s>
Windows	B-Device
NT	I-Device
DOS	B-Device
box	O
did	O
not	O
support	O
VCPI	O
either	O
.	O
</s>
<s>
VCPI	O
also	O
had	O
a	O
comparatively	O
limited	O
scope	O
in	O
that	O
it	O
allowed	O
a	O
protected	B-Application
mode	I-Application
DOS	B-Device
program	O
to	O
run	O
only	O
when	O
the	O
program	O
was	O
started	O
from	O
DOS	B-Device
already	O
running	O
inside	O
a	O
virtual	B-Application
8086	I-Application
mode	I-Application
task	O
.	O
</s>
<s>
(	O
This	O
was	O
typically	O
accomplished	O
through	O
a	O
memory	B-General_Concept
manager	I-General_Concept
operating	O
as	O
a	O
virtual	O
 [ mode ] 	O
control	O
program	O
for	O
the	O
processor	O
.	O
)	O
</s>
<s>
Because	O
the	O
virtual	B-Application
8086	I-Application
mode	I-Application
isolates	O
programs	O
from	O
the	O
hardware	O
,	O
it	O
is	O
not	O
possible	O
for	O
a	O
program	O
to	O
switch	O
to	O
protected	B-Application
mode	I-Application
without	O
some	O
support	O
from	O
the	O
control	O
program	O
.	O
</s>
<s>
Between	O
1989	O
and	O
February	O
1990	O
an	O
alternative	O
specification	O
was	O
proposed	O
under	O
the	O
name	O
Extended	O
VCPI	O
(	O
XVCPI	O
)	O
by	O
a	O
number	O
of	O
companies	O
including	O
Intel	O
's	O
Software	O
Focus	O
Group	O
,	O
Lotus	O
,	O
Digital	O
Research	O
,	O
Interactive	B-Operating_System
Systems	I-Operating_System
,	O
Viewport	O
International	O
and	O
others	O
to	O
address	O
some	O
of	O
the	O
shortcomings	O
of	O
VCPI	O
and	O
better	O
exploit	O
the	O
memory	O
management	O
and	O
multitasking	O
capabilities	O
of	O
the	O
386	O
processor	O
.	O
</s>
<s>
It	O
was	O
used	O
by	O
a	O
small	O
number	O
of	O
products	O
including	O
operating	O
systems	O
like	O
Interactive	B-Operating_System
Unix	I-Operating_System
and	O
Concurrent	B-Operating_System
DOS	I-Operating_System
386	I-Operating_System
.	O
</s>
<s>
Since	O
February	O
1990	O
these	O
efforts	O
ultimately	O
succumbed	O
to	O
the	O
(	O
parallel	O
)	O
development	O
and	O
publication	O
of	O
the	O
DPMI	O
specification	O
in	O
May	O
1990	O
,	O
which	O
addressed	O
similar	O
problems	O
,	O
but	O
was	O
compatible	O
with	O
the	O
implementation	O
of	O
Microsoft	B-Application
Windows	I-Application
3.0	I-Application
to	O
be	O
released	O
the	O
same	O
year	O
.	O
</s>
<s>
In	O
February	O
1991	O
,	O
the	O
Multiuser	O
DOS	B-Device
Federation	O
(	O
MDOS	O
)	O
,	O
an	O
initiative	O
formed	O
in	O
July	O
1990	O
,	O
issued	O
a	O
statement	O
regarding	O
their	O
support	O
of	O
DPMI	O
.	O
</s>
