<s>
The	O
North	B-Architecture
Star	I-Architecture
Horizon	I-Architecture
was	O
a	O
popular	O
8-bit	O
S-100	B-Architecture
bus	I-Architecture
computer	O
introduced	O
in	O
October	O
1977	O
.	O
</s>
<s>
Like	O
most	O
S-100	O
machines	O
of	O
the	O
era	O
,	O
it	O
was	O
built	O
around	O
the	O
Zilog	B-General_Concept
Z80A	I-General_Concept
microprocessor	B-Architecture
,	O
and	O
typically	O
ran	O
the	O
CP/M	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
The	O
North	B-Architecture
Star	I-Architecture
Horizon	I-Architecture
was	O
one	O
of	O
the	O
first	O
computers	O
to	O
have	O
built	O
in	O
floppy	B-Device
drives	I-Device
as	O
well	O
as	O
being	O
one	O
of	O
the	O
first	O
personal	B-Device
computers	I-Device
to	O
have	O
a	O
hard	B-Device
disk	I-Device
drive	I-Device
.	O
</s>
<s>
The	O
empty	O
section	O
in	O
front	O
of	O
the	O
power	O
supply	O
normally	O
housed	O
one	O
or	O
two	O
floppy	B-Device
disk	I-Device
drives	I-Device
,	O
placed	O
on	O
their	O
side	O
so	O
the	O
slots	O
were	O
vertical	O
.	O
</s>
<s>
Although	O
a	O
few	O
logic	O
circuits	O
were	O
on	O
the	O
motherboard	O
,	O
primarily	O
for	O
I/O	B-General_Concept
functions	O
,	O
both	O
the	O
processor	O
and	O
the	O
memory	O
resided	O
in	O
separate	O
daughterboards	O
.	O
</s>
<s>
Capable	O
of	O
running	O
CP/M	B-Application
and	O
NSDOS	O
(	O
North	O
Star	O
's	O
proprietary	O
Disk	B-Operating_System
Operating	I-Operating_System
System	I-Operating_System
)	O
,	O
a	O
standard	O
North	O
Star	O
system	O
sported	O
one	O
or	O
two	O
hard-sectored	B-Architecture
5.25	O
inch	O
floppy	B-Device
disk	I-Device
drives	I-Device
and	O
a	O
serial	B-Protocol
interface	I-Protocol
to	O
which	O
one	O
could	O
connect	O
a	O
terminal	B-General_Concept
to	O
interact	O
with	O
it	O
.	O
</s>
<s>
NSDOS	O
included	O
North	B-Language
Star	I-Language
BASIC	I-Language
,	O
a	O
slightly	O
non-standard	O
dialect	O
of	O
BASIC	O
,	O
where	O
some	O
standard	O
BASIC	O
commands	O
of	O
the	O
day	O
had	O
been	O
changed	O
,	O
probably	O
to	O
avoid	O
potential	O
legal	O
issues	O
.	O
</s>
<s>
Two	O
examples	O
of	O
this	O
were	O
the	O
EXAM	O
and	O
FILL	O
commands	O
,	O
which	O
took	O
the	O
place	O
of	O
the	O
more	O
common	O
PEEK	B-Language
and	I-Language
POKE	I-Language
.	O
</s>
<s>
The	O
Horizon	O
found	O
a	O
niche	O
in	O
University	O
environments	O
where	O
its	O
inbuilt	O
S-100	B-Architecture
bus	I-Architecture
could	O
be	O
used	O
to	O
interface	O
it	O
to	O
a	O
variety	O
of	O
control	O
systems	O
.	O
</s>
<s>
North	O
Star	O
released	O
a	O
hard	B-Device
disk	I-Device
version	O
,	O
with	O
an	O
internal	O
full	O
height	O
5MB	O
MFM	B-Protocol
drive	O
.	O
</s>
<s>
They	O
also	O
released	O
an	O
S-100	O
card	O
with	O
integrated	O
memory	O
and	O
two	O
serial	B-Protocol
ports	I-Protocol
which	O
allowed	O
up	O
to	O
eight	O
users	O
on	O
one	O
Horizon	O
,	O
each	O
with	O
their	O
own	O
CPU	O
sharing	O
the	O
disk	O
and	O
other	O
resources	O
.	O
</s>
<s>
This	O
operated	O
under	O
TurboDOS	B-Operating_System
,	O
a	O
multi	O
user	O
CP/M	B-Application
variant	O
with	O
some	O
Unix-like	B-Operating_System
features	O
.	O
</s>
