<s>
PC-MOS/386	B-Application
is	O
a	O
multi-user	B-Operating_System
,	O
multitasking	B-Operating_System
computer	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
produced	O
by	O
The	O
Software	O
Link	O
(	O
TSL	O
)	O
,	O
announced	O
at	O
COMDEX	O
in	O
November	O
1986	O
for	B-Language
February	O
1987	O
release	O
.	O
</s>
<s>
PC-MOS/386	B-Application
,	O
a	O
successor	O
to	O
PC-MOS	O
,	O
can	O
run	O
many	O
MS-DOS	B-Application
programs	O
on	O
the	O
host	O
machine	O
or	O
a	O
terminal	B-General_Concept
connected	O
to	O
it	O
.	O
</s>
<s>
Unlike	O
MS-DOS	B-Application
,	O
PC-MOS/386	B-Application
is	O
optimized	O
for	B-Language
the	O
Intel	B-General_Concept
80386	I-General_Concept
processor	O
;	O
however	O
early	O
versions	O
will	O
run	O
on	O
any	O
x86	B-Operating_System
computer	O
.	O
</s>
<s>
PC-MOS/386	B-Application
used	O
to	O
be	O
proprietary	B-Application
,	O
but	O
it	O
was	O
released	O
as	O
open-source	B-Application
software	I-Application
in	O
2017	O
.	O
</s>
<s>
The	O
last	O
commercial	O
version	O
produced	O
was	O
v5.01	O
,	O
compatible	O
with	O
MS-DOS	B-Application
5	O
.	O
</s>
<s>
It	O
required	O
a	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
(	O
MMU	O
)	O
to	O
support	O
memory	O
protection	O
,	O
so	O
was	O
not	O
compatible	O
with	O
8086	B-General_Concept
and	O
8088	B-Device
processors	O
.	O
</s>
<s>
MMU	O
support	O
for	B-Language
286	O
class	O
machines	O
was	O
provided	O
using	O
a	O
proprietary	B-Application
hardware	O
shim	B-General_Concept
inserted	O
between	O
the	O
processor	O
and	O
its	O
socket	O
.	O
</s>
<s>
386	B-General_Concept
machines	O
did	O
not	O
require	O
any	O
special	O
hardware	O
.	O
</s>
<s>
Multi-user	B-Operating_System
operation	O
suffered	O
from	O
the	O
limitations	O
of	O
the	O
day	O
including	O
the	O
inability	O
of	O
the	O
processor	O
to	O
schedule	O
and	O
partition	O
running	O
processes	O
.	O
</s>
<s>
Typically	O
swapping	O
from	O
a	O
foreground	O
to	O
a	O
background	O
process	O
on	O
the	O
same	O
terminal	B-General_Concept
used	O
the	O
keyboard	O
to	O
generate	O
an	O
interrupt	O
and	O
then	O
swap	O
the	O
processes	O
.	O
</s>
<s>
PC-MOS	O
terminals	O
could	O
be	O
x86	B-Operating_System
computers	O
running	O
terminal	B-Application
emulation	I-Application
software	O
communicating	O
at	O
9600	O
or	O
19200	O
baud	O
,	O
connected	O
via	O
serial	O
cables	O
.	O
</s>
<s>
However	O
,	O
the	O
greatest	O
benefit	O
was	O
reached	O
when	O
using	O
standard	O
,	O
"	O
dumb	O
"	O
terminals	O
which	O
shared	O
the	O
resources	O
of	O
the	O
then	O
central	O
386-based	O
processor	O
.	O
</s>
<s>
Speeds	O
above	O
this	O
required	O
specialized	O
hardware	O
boards	O
which	O
increased	O
cost	O
,	O
but	O
the	O
speed	O
was	O
not	O
a	O
serious	O
limitation	O
for	B-Language
interacting	O
with	O
text-based	O
programs	O
.	O
</s>
<s>
There	O
was	O
a	O
year	O
2000	O
problem-like	O
issue	O
in	O
this	O
operating	B-General_Concept
system	I-General_Concept
,	O
first	O
manifesting	O
on	O
1	O
August	O
2012	O
rather	O
than	O
1	O
January	O
2000	O
:	O
files	O
created	O
on	O
the	O
system	O
from	O
this	O
date	O
on	O
would	O
no	O
longer	O
work	O
.	O
</s>
<s>
On	O
21	O
July	O
2017	O
PCMOS/386	O
was	O
relicensed	O
under	O
GPL	O
v3	O
and	O
its	O
source	O
code	O
uploaded	O
to	O
GitHub	B-Application
,	O
with	O
the	O
"	O
year	O
2012	O
"	O
issue	O
corrected	O
.	O
</s>
<s>
Commands	B-Application
supported	O
by	O
PC-MOS	O
Version	O
4	O
are	O
:	O
</s>
