<s>
Z-DOS	B-Operating_System
is	O
a	O
discontinued	O
OEM	O
version	O
of	O
Microsoft	O
's	O
MS-DOS	B-Application
specifically	O
adapted	O
to	O
run	O
on	O
the	O
hardware	O
of	O
the	O
Zenith	B-Device
Z-100	I-Device
personal	O
computer	O
.	O
</s>
<s>
The	O
Z-100	B-Device
used	O
a	O
8086-family	B-Operating_System
microprocessor	O
,	O
(	O
the	O
Intel	B-Device
8088	I-Device
)	O
,	O
but	O
otherwise	O
had	O
a	O
completely	O
different	O
internal	O
architecture	O
from	O
the	O
IBM	O
PC	O
.	O
</s>
<s>
At	O
the	O
time	O
Microsoft	O
's	O
MS-DOS	B-Application
was	O
n't	O
specifically	O
geared	O
to	O
any	O
specific	O
hardware	O
platform	O
,	O
but	O
could	O
be	O
tailored	O
to	O
run	O
on	O
most	O
any	O
system	O
as	O
long	O
as	O
it	O
used	O
a	O
8086-compatible	O
microprocessor	O
,	O
a	O
situation	O
completely	O
like	O
with	O
the	O
popular	O
CP/M	B-Application
systems	O
of	O
the	O
time	O
,	O
which	O
typically	O
used	O
a	O
8080-compatible	O
(	O
8080	B-General_Concept
,	O
8085	B-General_Concept
and	O
Z80	B-General_Concept
among	O
others	O
)	O
microprocessor	O
.	O
</s>
<s>
In	O
order	O
to	O
achieve	O
this	O
,	O
MS-DOS	B-Application
,	O
like	O
CP/M	B-Application
,	O
relied	O
on	O
a	O
platform-specific	O
(	O
DOS	O
-	O
)	O
BIOS	B-Operating_System
,	O
which	O
had	O
to	O
be	O
written	O
for	O
the	O
target	O
machine	O
,	O
so	O
that	O
the	O
hardware-independent	O
DOS	O
kernel	O
could	O
run	O
on	O
it	O
.	O
</s>
<s>
Beside	O
IBM	O
's	O
OEM	O
version	O
of	O
MS-DOS	B-Application
released	O
as	O
PC	O
DOS	O
there	O
were	O
dozens	O
of	O
other	O
OEM	O
versions	O
of	O
MS-DOS	B-Application
geared	O
to	O
a	O
specific	O
non-IBM-compatible	O
OEM	O
hardwareamong	O
them	O
Zenith	O
's	O
Z-DOS	B-Operating_System
.	O
</s>
<s>
Only	O
later	O
,	O
when	O
almost	O
100%	O
IBM-compatible	O
clones	B-General_Concept
became	O
the	O
norm	O
,	O
"	O
MS-DOS	B-Application
"	O
became	O
the	O
generic	O
version	O
which	O
could	O
run	O
on	O
most	O
of	O
them	O
.	O
</s>
<s>
This	O
generic	O
version	O
of	O
MS-DOS	B-Application
,	O
however	O
,	O
could	O
not	O
run	O
on	O
the	O
older	O
non-IBM-compatible	O
machines	O
like	O
the	O
Z-100	B-Device
.	O
</s>
