<s>
The	O
Convergent	B-Operating_System
Technologies	I-Operating_System
Operating	I-Operating_System
System	I-Operating_System
,	O
also	O
known	O
variously	O
as	O
CTOS	B-Operating_System
,	O
BTOS	B-Operating_System
and	O
STARSYS	O
,	O
is	O
a	O
discontinued	O
modular	O
,	O
message-passing	B-Architecture
,	O
multiprocess-based	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
CTOS	B-Operating_System
had	O
many	O
innovative	O
features	O
for	O
its	O
time	O
.	O
</s>
<s>
It	O
was	O
possible	O
to	O
custom-link	O
the	O
operating	B-General_Concept
system	I-General_Concept
to	O
add	O
or	O
delete	O
features	O
.	O
</s>
<s>
CTOS	B-Operating_System
supported	O
a	O
transparent	O
peer-to-peer	O
network	O
carried	O
over	O
serial	O
RS-422	O
cables	O
(	O
daisy-chain	O
topology	O
)	O
and	O
in	O
later	O
versions	O
carried	O
over	O
twisted	O
pair	O
(	O
star	O
topology	O
)	O
with	O
RS-422	O
adapters	O
.	O
</s>
<s>
The	O
workstations	O
,	O
normally	O
diskless	B-Device
,	O
were	O
booted	B-Device
over	I-Device
the	I-Device
cluster	I-Device
network	I-Device
from	O
the	O
master	O
,	O
and	O
could	O
optionally	O
be	O
locally	O
booted	O
from	O
attached	O
hard	O
drives	O
.	O
</s>
<s>
The	O
Inter-process	B-Operating_System
communication	I-Operating_System
(	O
IPC	O
)	O
is	O
primarily	O
based	O
on	O
the	O
"	O
request	O
"	O
and	O
"	O
respond	O
"	O
messaging	O
foundation	O
that	O
enhanced	O
the	O
Enterprise	O
Application	O
Integration	O
among	O
services	O
for	O
both	O
internal	O
and	O
external	O
environments	O
.	O
</s>
<s>
Thus	O
CTOS	B-Operating_System
was	O
well	O
known	O
for	O
the	O
message-based	B-Architecture
Microkernel	B-Operating_System
Architecture	O
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
maintains	O
the	O
exchanges	O
,	O
message	O
queues	O
,	O
scheduling	O
,	O
control	O
,	O
message	B-Architecture
passing	I-Architecture
,	O
etc.	O
,	O
while	O
the	O
service	O
manages	O
the	O
messages	O
at	O
its	O
own	O
exchange	O
using	O
"	O
wait	O
"	O
,	O
"	O
check	O
"	O
,	O
and	O
"	O
respond	O
"	O
macros	O
.	O
</s>
<s>
CTOS	B-Operating_System
ran	O
on	O
Intel	B-Operating_System
x86	I-Operating_System
computers	O
,	O
and	O
could	O
run	O
concurrently	O
with	O
Windows	B-Device
NT	I-Device
on	O
Unisys	O
PC	O
.	O
</s>
<s>
The	O
assembler	O
was	O
very	O
advanced	O
,	O
with	O
a	O
Lisp-like	O
pattern-matching	O
macro	O
facility	O
unmatched	O
by	O
almost	O
any	O
other	O
assembler	O
before	O
or	O
since	O
.	O
</s>
<s>
Most	O
of	O
the	O
system	O
programs	O
were	O
written	O
in	O
PL/M	B-Language
,	O
an	O
ALGOL-like	B-Language
language	O
from	O
Intel	O
which	O
compiled	O
directly	O
to	O
object	B-Language
code	I-Language
without	O
a	O
runtime	B-Library
library	I-Library
.	O
</s>
<s>
The	O
word	B-General_Concept
processor	I-General_Concept
was	O
one	O
of	O
the	O
first	O
screen-oriented	O
editors	O
with	O
many	O
high-powered	O
features	O
,	O
such	O
as	O
multiple	O
views	O
of	O
the	O
same	O
file	O
,	O
cut/copy/paste	O
,	O
unlimited	O
undo/redo	O
,	O
no	O
typing	O
lost	O
after	O
a	O
crash	O
or	O
power	O
failure	O
,	O
user-selectable	O
fonts	O
,	O
and	O
much	O
more	O
.	O
</s>
<s>
The	O
BTOS	B-Operating_System
version	O
allowed	O
scripts	O
to	O
be	O
written	O
that	O
included	O
opening	O
the	O
spreadsheet	O
for	O
user	O
input	O
,	O
then	O
automatically	O
printing	O
graphs	O
based	O
on	O
the	O
input	O
data	O
.	O
</s>
<s>
Convergent	O
Technologies	O
 '	O
first	O
product	O
was	O
the	O
IWS	O
(	O
Integrated	O
Workstation	O
)	O
based	O
on	O
the	O
Intel	B-General_Concept
8086	I-General_Concept
processor	O
,	O
which	O
had	O
CTOS	B-Operating_System
as	O
its	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
This	O
was	O
a	O
modular	O
operating	B-General_Concept
system	I-General_Concept
with	O
built-in	O
local	B-General_Concept
area	I-General_Concept
networking	I-General_Concept
.	O
</s>
<s>
CTOS	B-Operating_System
supported	O
multiple	O
processes	O
or	O
threads	O
,	O
and	O
message-based	B-Architecture
interprocess	B-Operating_System
communication	I-Operating_System
.	O
</s>
<s>
Companies	O
that	O
licensed	O
CTOS	B-Operating_System
included	O
Bull	O
(	O
STARSYS	O
)	O
,	O
and	O
Burroughs	O
(	O
BTOS	B-Operating_System
)	O
who	O
later	O
merged	O
with	O
Sperry	O
to	O
become	O
Unisys	O
.	O
</s>
<s>
At	O
its	O
peak	O
,	O
CTOS	B-Operating_System
had	O
over	O
800,000	O
users	O
worldwide	O
.	O
</s>
<s>
CTOS	B-Operating_System
is	O
no	O
longer	O
marketed	O
to	O
new	O
customers	O
.	O
</s>
<s>
The	O
Coast	O
Guard	O
used	O
the	O
operating	B-General_Concept
system	I-General_Concept
from	O
approximately	O
1984	O
until	O
2000	O
.	O
</s>
<s>
In	O
Australia	O
,	O
CTOS/BTOS	O
was	O
used	O
by	O
the	O
Trade	O
Practices	O
Commission	O
,	O
NSW	O
Auditor-General	O
'	O
s	O
,	O
CSIRO	O
,	O
Commonwealth	O
Electoral	O
Office	O
,	O
Western	O
Australia	O
Prisons	O
Department	O
and	O
many	O
commercial	O
banks	O
.	O
</s>
<s>
Diskless	B-Device
workstations	I-Device
(	O
e.g.	O
,	O
Bull	O
)	O
based	O
on	O
Convergent	O
's	O
NGEN	O
used	O
the	O
Intel	B-Device
80186	I-Device
processor	O
,	O
a	O
processor	O
seldom	O
used	O
by	O
standard	O
PCs	O
.	O
</s>
<s>
Progress	O
Software	O
Corporation	O
made	O
a	O
commercial	O
database	O
application	O
for	O
CTOS	B-Operating_System
that	O
was	O
in	O
4GL	B-Language
.	O
</s>
<s>
There	O
was	O
a	O
port	O
of	O
CorelDRAW	B-Application
for	O
CTOS	B-Operating_System
running	O
the	O
Presentation	B-Device
Manager	I-Device
.	O
</s>
