<s>
Proprietary	B-Device
hardware	I-Device
is	O
computer	B-Architecture
hardware	I-Architecture
whose	O
interface	B-Application
is	O
controlled	O
by	O
the	O
proprietor	O
,	O
often	O
under	O
patent	O
or	O
trade-secret	O
protection	O
.	O
</s>
<s>
Historically	O
,	O
most	O
early	O
computer	B-Architecture
hardware	I-Architecture
was	O
designed	O
as	O
proprietary	B-Application
until	O
the	O
1980s	O
,	O
when	O
IBM	B-Device
PC	I-Device
changed	O
this	O
paradigm	O
.	O
</s>
<s>
Earlier	O
,	O
in	O
the	O
1970s	O
,	O
many	O
vendors	O
tried	O
to	O
challenge	O
IBM	O
's	O
monopoly	O
in	O
the	O
mainframe	B-Architecture
computer	I-Architecture
market	O
by	O
reverse	O
engineering	O
and	O
producing	O
hardware	B-Architecture
components	O
electrically	O
compatible	O
with	O
expensive	O
equipment	O
and	O
(	O
usually	O
)	O
able	O
to	O
run	O
the	O
same	O
software	O
.	O
</s>
<s>
Those	O
vendors	O
were	O
nicknamed	O
plug	B-Device
compatible	I-Device
manufacturers	I-Device
(	O
PCMs	O
)	O
.	O
</s>
