<s>
Harmony	B-Operating_System
is	O
an	O
experimental	O
computer	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
(	O
OS	O
)	O
developed	O
at	O
the	O
National	O
Research	O
Council	O
Canada	O
in	O
Ottawa	O
.	O
</s>
<s>
It	O
is	O
a	O
second-generation	O
message	B-Architecture
passing	I-Architecture
system	O
that	O
was	O
also	O
used	O
as	O
the	O
basis	O
for	O
several	O
research	O
projects	O
,	O
including	O
robotics	O
sensing	O
and	O
graphical	O
workstation	B-Device
development	O
.	O
</s>
<s>
Harmony	B-Operating_System
was	O
actively	O
developed	O
throughout	O
the	O
1980s	O
and	O
into	O
the	O
mid-1990s	O
.	O
</s>
<s>
Harmony	B-Operating_System
was	O
a	O
successor	O
to	O
the	O
Thoth	B-Operating_System
system	O
developed	O
at	O
the	O
University	O
of	O
Waterloo	O
.	O
</s>
<s>
Work	O
on	O
Harmony	B-Operating_System
began	O
at	O
roughly	O
the	O
same	O
time	O
as	O
that	O
on	O
the	O
Verex	O
kernel	O
developed	O
at	O
the	O
University	O
of	O
British	O
Columbia	O
.	O
</s>
<s>
David	O
Cheriton	O
was	O
involved	O
in	O
both	O
Thoth	B-Operating_System
and	O
Verex	O
,	O
and	O
would	O
later	O
go	O
on	O
to	O
develop	O
the	O
V	B-Operating_System
System	I-Operating_System
at	O
Stanford	O
University	O
.	O
</s>
<s>
Harmony	B-Operating_System
's	O
principal	O
developers	O
included	O
W	O
.	O
Morven	O
Gentleman	O
,	O
Stephen	O
A	O
.	O
MacKay	O
,	O
Darlene	O
A	O
.	O
Stewart	O
,	O
and	O
Marceli	O
Wein	O
.	O
</s>
<s>
Early	O
ports	O
of	O
the	O
system	O
existed	O
for	O
a	O
variety	O
of	O
Motorola	O
68000-based	O
computers	O
,	O
including	O
ones	O
using	O
the	O
VMEbus	B-Architecture
and	O
Multibus	B-Protocol
backplanes	O
and	O
in	O
particular	O
the	O
Multibus-based	O
Chorus	O
multiprocessor	B-Operating_System
system	O
at	O
Waterloo	O
.	O
</s>
<s>
Other	O
hosts	O
included	O
the	O
Atari	O
520	O
or	O
1040	O
ST	O
.	O
A	O
port	O
also	O
existed	O
for	O
the	O
Digital	O
Equipment	O
Corporation	O
VAX	B-Device
.	O
</s>
<s>
Harmony	B-Operating_System
achieved	O
formal	O
verification	O
in	O
1995	O
.	O
</s>
<s>
Harmony	B-Operating_System
was	O
designed	O
as	O
a	O
real-time	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
(	O
RTOS	B-Operating_System
)	O
for	O
robot	B-Algorithm
control	O
.	O
</s>
<s>
It	O
is	O
a	O
multitasking	B-Operating_System
,	O
multiprocessing	B-Operating_System
system	O
.	O
</s>
<s>
It	O
is	O
not	O
multi-user	B-Operating_System
.	O
</s>
<s>
Harmony	B-Operating_System
provided	O
a	O
runtime	B-Device
system	I-Device
(	O
environment	O
)	O
only	O
;	O
development	O
took	O
place	O
on	O
a	O
separate	O
system	O
,	O
originally	O
an	O
Apple	O
Macintosh	B-Device
.	O
</s>
<s>
For	O
each	O
processor	O
in	O
the	O
system	O
,	O
an	O
image	O
is	O
created	O
that	O
combines	O
Harmony	B-Operating_System
with	O
the	O
one	O
multitask	O
program	O
for	O
that	O
processor	O
at	O
link	B-Application
time	O
,	O
an	O
exception	O
being	O
a	O
case	O
where	O
the	O
kernel	O
is	O
programmed	O
into	O
a	O
read-only	B-Device
memory	I-Device
(	O
ROM	B-Device
)	O
.	O
</s>
<s>
Although	O
the	O
term	O
did	O
not	O
appear	O
in	O
the	O
original	O
papers	O
,	O
Harmony	B-Operating_System
was	O
later	O
referred	O
to	O
as	O
a	O
microkernel	B-Operating_System
.	O
</s>
<s>
A	O
key	O
in	O
Harmony	B-Operating_System
is	O
its	O
use	O
of	O
the	O
term	O
task	O
,	O
which	O
in	O
Harmony	B-Operating_System
is	O
defined	O
as	O
the	O
"	O
unit	O
of	O
sequential	O
and	O
synchronous	O
execution	O
"	O
and	O
"	O
the	O
unit	O
of	O
resource	O
ownership	O
"	O
.	O
</s>
<s>
Intertask	O
communication	O
is	O
provided	O
mostly	O
by	O
synchronous	O
message	B-Architecture
passing	I-Architecture
and	O
four	O
associated	O
primitives	O
.	O
</s>
<s>
Input/output	B-General_Concept
uses	O
a	O
data	B-General_Concept
stream	I-General_Concept
model	O
.	O
</s>
<s>
Harmony	B-Operating_System
is	O
connection-oriented	O
in	O
that	O
tasks	O
that	O
communicate	O
with	O
each	O
other	O
often	O
maintain	O
state	O
information	O
about	O
each	O
other	O
.	O
</s>
<s>
In	O
contrast	O
with	O
some	O
other	O
distributed	O
systems	O
,	O
connections	O
in	O
Harmony	B-Operating_System
are	O
inexpensive	O
.	O
</s>
<s>
An	O
advanced	O
debugger	O
called	O
Melody	O
was	O
developed	O
for	O
Harmony	B-Operating_System
at	O
the	O
Advanced	O
Real-Time	O
Toolset	O
Laboratory	O
at	O
Carleton	O
University	O
.	O
</s>
<s>
It	O
was	O
later	O
commercialized	O
as	O
Remedy	B-Application
.	O
</s>
<s>
The	O
Harmony	B-Operating_System
kernel	O
underpinned	O
the	O
Actra	O
project	O
—	O
a	O
multiprocessing	B-Operating_System
,	O
multitasking	B-Operating_System
Smalltalk	O
.	O
</s>
<s>
Harmony	B-Operating_System
was	O
used	O
in	O
the	O
multitasking	B-Operating_System
,	O
multiprocessor	B-Operating_System
Adagio	O
robotics	O
simulation	O
workstation	B-Device
.	O
</s>
<s>
Concepts	O
from	O
both	O
Harmony	B-Operating_System
and	O
Adagio	O
influenced	O
the	O
design	O
of	O
the	O
Smalltalk-based	O
Eva	O
event	O
driven	O
user	O
interface	O
builder	O
.	O
</s>
<s>
Harmony	B-Operating_System
was	O
used	O
as	O
the	O
underlying	O
OS	O
for	O
several	O
experimental	O
robotic	O
systems	O
.	O
</s>
<s>
Harmony	B-Operating_System
was	O
commercialized	O
by	O
the	O
Taurus	O
Computer	O
Products	O
division	O
of	O
Canadian	O
industrial	O
computer	O
company	O
Dy4	O
.	O
</s>
<s>
When	O
Dy4	O
closed	O
down	O
their	O
software	O
division	O
,	O
four	O
of	O
Taurus	O
 '	O
former	O
developers	O
founded	O
Precise	O
Software	O
Technologies	O
and	O
continued	O
developing	O
the	O
OS	O
as	O
Precise/MPX	O
,	O
the	O
predecessor	O
to	O
their	O
later	O
Precise/MQX	O
product	O
.	O
</s>
<s>
Another	O
commercial	O
operating	B-General_Concept
system	I-General_Concept
derived	O
from	O
Harmony	B-Operating_System
is	O
the	O
Unison	O
OS	O
from	O
Rowebot	O
Research	O
Inc	O
.	O
</s>
