<s>
RSX-11	B-Application
is	O
a	O
discontinued	O
family	O
of	O
multi-user	B-Operating_System
real-time	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
for	O
PDP-11	B-Device
computers	O
created	O
by	O
Digital	O
Equipment	O
Corporation	O
.	O
</s>
<s>
In	O
widespread	O
use	O
through	O
the	O
late	O
1970s	O
and	O
early	O
1980s	O
,	O
RSX-11	B-Application
was	O
influential	O
in	O
the	O
development	O
of	O
later	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
VMS	B-Operating_System
and	O
Windows	B-Device
NT	I-Device
.	O
</s>
<s>
RSX-11	B-Application
began	O
as	O
a	O
port	O
to	O
the	O
PDP-11	B-Device
architecture	O
of	O
the	O
earlier	O
RSX-15	O
operating	B-General_Concept
system	I-General_Concept
for	O
the	O
PDP-15	B-Device
minicomputer	O
,	O
first	O
released	O
in	O
1971	O
.	O
</s>
<s>
RSX-11B	O
then	O
evolved	O
into	O
the	O
fully	O
fledged	O
RSX-11D	O
disk-based	O
operating	B-General_Concept
system	I-General_Concept
,	O
which	O
first	O
appeared	O
on	O
the	O
PDP-11/40	B-Device
and	O
PDP-11/45	B-Device
in	O
early	O
1973	O
.	O
</s>
<s>
giving	O
birth	O
to	O
RSX-11M	B-Application
,	O
first	O
released	O
in	O
1973	O
.	O
</s>
<s>
From	O
1971	O
to	O
1976	O
,	O
the	O
RSX-11M	B-Application
project	O
was	O
spearheaded	O
by	O
noted	O
operating	B-General_Concept
system	I-General_Concept
designer	O
Dave	O
Cutler	O
,	O
then	O
at	O
his	O
first	O
project	O
.	O
</s>
<s>
Principles	O
first	O
tried	O
in	O
RSX-11M	B-Application
appear	O
also	O
in	O
later	O
designs	O
led	O
by	O
Cutler	O
,	O
DEC	O
's	O
VMS	B-Operating_System
and	O
Microsoft	O
's	O
Windows	B-Device
NT	I-Device
.	O
</s>
<s>
Under	O
the	O
direction	O
of	O
Ron	O
McLean	O
a	O
derivative	O
of	O
RSX-11M	B-Application
,	O
called	O
RSX-20F	O
,	O
was	O
developed	O
to	O
run	O
on	O
the	O
PDP-11/40	B-Device
front-end	O
processor	O
for	O
the	O
KL10	B-Device
PDP-10	B-Device
CPU	O
.	O
</s>
<s>
Support	O
for	O
the	O
22-bit	O
PDP-11/70	B-Device
system	O
was	O
added	O
.	O
</s>
<s>
Wolfendale	O
,	O
originally	O
from	O
the	O
UK	O
,	O
also	O
set	O
up	O
the	O
team	O
that	O
designed	O
and	O
prototyped	O
the	O
Interactive	B-Operating_System
Application	I-Operating_System
System	I-Operating_System
(	O
IAS	B-Operating_System
)	O
operating	B-General_Concept
system	I-General_Concept
in	O
the	O
UK	O
;	O
IAS	B-Operating_System
was	O
a	O
variant	O
of	O
RSX-11D	O
more	O
suitable	O
for	O
time	B-General_Concept
sharing	I-General_Concept
.	O
</s>
<s>
Later	O
development	O
and	O
release	O
of	O
IAS	B-Operating_System
was	O
led	O
by	O
Andy	O
Wilson	O
,	O
in	O
Digital	O
's	O
UK	O
facilities	O
.	O
</s>
<s>
Below	O
are	O
estimated	O
release	O
dates	O
for	O
RSX-11	B-Application
and	O
IAS	B-Operating_System
.	O
</s>
<s>
RSX-11S	B-Application
is	O
a	O
proper	O
subset	O
of	O
RSX-11M	B-Application
,	O
so	O
release	O
dates	O
are	O
always	O
assumed	O
to	O
be	O
the	O
same	O
as	O
the	O
corresponding	O
version	O
of	O
RSX-11M	B-Application
.	O
</s>
<s>
On	O
the	O
other	O
side	O
,	O
RSX-11M	B-Application
Plus	O
is	O
an	O
enhanced	O
version	O
of	O
RSX-11M	B-Application
,	O
so	O
it	O
is	O
expected	O
to	O
be	O
later	O
than	O
the	O
corresponding	O
version	O
of	O
RSX-11M	B-Application
.	O
</s>
<s>
Date	O
RSX-11A	O
,	O
CRSX-11DIASRSX-11M	O
,	O
SRSX-11M	O
PlusMicro/RSX	O
Comment	O
March	O
1973	O
RSX-11A	O
1.0	O
May	O
1973	O
Originally	O
published	O
on	O
CD-ROM	B-Device
,	O
copy	O
hosted	O
on	O
the	O
website	O
of	O
Gordon	O
BellRSX	O
11D	O
1.0	O
December	O
1973Data	O
from	O
the	O
labels	O
of	O
the	O
distribution	O
paper	O
tapes	O
.	O
</s>
<s>
See	O
:	O
RSX-11M	B-Application
1.0	O
June	O
1975RSX-11D	O
6.2	O
Final	O
version	O
of	O
RSX-11D	O
September	O
1975RSX-11M	O
2.0RSX-11S	O
2.0	O
RSX-11S	B-Application
1.0	O
never	O
existed	O
December	O
1975IAS	O
1.0	O
April	O
1977RSX-11M	O
3.0RSX-11S	O
3.0	O
December	O
1977RSX-11M	O
3.1RSX-11S	O
3.1May	O
1979RSX-11M	O
3.2RSX-11S	O
3.2RSX-11M	O
Plus	O
1.0	O
bef	O
.	O
</s>
<s>
RSX-11	B-Application
is	O
proprietary	B-Application
software	I-Application
.	O
</s>
<s>
Therefore	O
,	O
no	O
part	O
of	O
it	O
is	O
open	B-Application
source	I-Application
.	O
</s>
<s>
However	O
a	O
copy	O
of	O
the	O
kernel	B-Operating_System
source	O
is	O
present	O
in	O
every	O
RSX	O
distribution	O
,	O
because	O
it	O
was	O
used	O
during	O
the	O
system	B-Application
generation	I-Application
process	O
.	O
</s>
<s>
The	O
notable	O
exception	O
to	O
this	O
rule	O
is	O
Micro-RSX	O
,	O
which	O
came	O
with	O
a	O
pre-generated	O
autoconfiguring	O
binary	O
kernel	B-Operating_System
.	O
</s>
<s>
Ownership	O
of	O
RSX-11S	B-Application
,	O
RSX-11M	B-Application
,	O
RSX-11M	B-Application
Plus	O
and	O
Micro/RSX	O
was	O
transferred	O
from	O
Digital	O
to	O
Mentec	O
Inc	O
.	O
in	O
March	O
1994	O
as	O
part	O
of	O
a	O
broader	O
agreement	O
.	O
</s>
<s>
Mentec	O
Inc	O
.	O
was	O
the	O
US	O
subsidiary	O
of	O
Mentec	O
Limited	O
,	O
an	O
Irish	O
firm	O
specializing	O
in	O
PDP-11	B-Device
hardware	O
and	O
software	O
support	O
.	O
</s>
<s>
The	O
PDP-11	B-Device
software	O
,	O
which	O
was	O
owned	O
by	O
Mentec	O
Inc	O
.	O
was	O
then	O
bought	O
by	O
XX2247	O
LLC	O
,	O
which	O
is	O
the	O
owner	O
of	O
the	O
software	O
today	O
.	O
</s>
<s>
Hobbyists	O
can	O
run	O
RSX-11M	B-Application
(	O
version	O
4.3	O
or	O
earlier	O
)	O
and	O
RSX-11M	B-Application
Plus	O
(	O
version	O
3.0	O
or	O
earlier	O
)	O
on	O
the	O
SIMH	B-Application
emulator	B-Application
thanks	O
to	O
a	O
free	O
license	O
granted	O
in	O
May	O
1998	O
by	O
Mentec	O
Inc	O
.	O
</s>
<s>
Legal	O
ownership	O
of	O
RSX-11A	O
,	O
RSX-11B	O
,	O
RSX-11C	O
,	O
RSX-11D	O
,	O
and	O
IAS	B-Operating_System
never	O
changed	O
hands	O
;	O
therefore	O
it	O
passed	O
to	O
Compaq	O
when	O
it	O
acquired	O
Digital	O
in	O
1998	O
and	O
then	O
to	O
Hewlett-Packard	O
in	O
2002	O
.	O
</s>
<s>
No	O
new	O
commercial	O
licenses	O
have	O
been	O
issued	O
since	O
at	O
least	O
October	O
1979	O
(	O
RSX-11A	O
,	O
RSX-11B	O
,	O
RSX-11C	O
)	O
or	O
1990	O
(	O
IAS	B-Operating_System
)	O
,	O
and	O
none	O
of	O
these	O
operating	B-General_Concept
systems	I-General_Concept
have	O
ever	O
been	O
licensed	O
for	O
hobbyist	O
use	O
.	O
</s>
<s>
RSX-11B	O
–	O
small	O
real	O
time	O
executive	O
based	O
on	O
RSX-11C	O
with	O
support	O
for	O
disk	O
I/O	B-General_Concept
.	O
</s>
<s>
RSX-11B	O
programs	O
used	O
DOS-11	O
macros	O
to	O
perform	O
disk	O
I/O	B-General_Concept
.	O
</s>
<s>
IAS	B-Operating_System
–	O
a	O
timesharing-oriented	O
variant	O
of	O
RSX-11D	O
released	O
at	O
about	O
the	O
same	O
time	O
as	O
the	O
PDP-11/70	B-Device
.	O
</s>
<s>
The	O
first	O
version	O
of	O
RSX	O
to	O
include	O
DCL	B-Operating_System
(	O
Digital	B-Operating_System
Command	I-Operating_System
Language	I-Operating_System
)	O
,	O
which	O
in	O
IAS	B-Operating_System
is	O
known	O
by	O
its	O
original	O
name	O
,	O
PDS	O
(	O
Program	O
Development	O
System	O
)	O
.	O
</s>
<s>
RSX-11S	B-Application
–	O
a	O
memory-resident	O
version	O
of	O
RSX-11M	B-Application
used	O
in	O
embedded	O
real-time	O
applications	O
.	O
</s>
<s>
RSX-11S	B-Application
applications	O
were	O
developed	O
under	O
RSX-11M	B-Application
.	O
</s>
<s>
RSX-11M-Plus	O
–	O
a	O
much	O
extended	O
version	O
of	O
RSX-11M	B-Application
,	O
originally	O
designed	O
to	O
support	O
the	O
multi-processor	O
PDP-11/74	O
,	O
a	O
computer	O
that	O
was	O
never	O
released	O
,	O
but	O
RSX-11M-Plus	O
was	O
then	O
used	O
widely	O
as	O
a	O
standard	O
operating	B-General_Concept
system	I-General_Concept
on	O
the	O
PDP-11/70	B-Device
.	O
</s>
<s>
RSX-11M-Plus	O
also	O
ran	O
on	O
PDP-11/44	B-Device
,	O
PDP-11/84	O
,	O
PDP-11/94	O
(	O
Unibus	O
machines	O
)	O
,	O
as	O
well	O
as	O
PDP-11/73	O
,	O
PDP-11/83	O
,	O
and	O
PDP-11/93	O
(	O
Qbus	O
machines	O
)	O
.	O
</s>
<s>
One	O
of	O
the	O
advantages	O
of	O
RSX-11M-Plus	O
over	O
RSX-11M	B-Application
was	O
that	O
larger	O
programs	O
could	O
be	O
created	O
.	O
</s>
<s>
This	O
was	O
achieved	O
by	O
having	O
the	O
task	O
builder	O
(	O
the	O
linker	O
)	O
build	O
the	O
program	O
to	O
use	O
the	O
separate	O
instruction	O
and	O
data	O
space	O
feature	O
of	O
some	O
PDP-11	B-Device
models	O
to	O
put	O
executable	O
code	O
and	O
data	O
into	O
separate	O
address	O
spaces	O
.	O
</s>
<s>
This	O
also	O
allowed	O
programs	O
to	O
run	O
faster	O
,	O
as	O
it	O
reduced	O
the	O
need	O
for	O
"	O
overlays	B-General_Concept
"	O
,	O
in	O
which	O
you	O
could	O
overlay	B-General_Concept
object	O
modules	O
at	O
task	O
build	O
time	O
,	O
for	O
very	O
large	O
programs	O
.	O
</s>
<s>
Overlays	B-General_Concept
were	O
specified	O
in	O
a	O
task	O
build	O
command	O
file	O
.	O
</s>
<s>
Micro/RSX	O
–	O
a	O
pre-generated	O
full	O
version	O
of	O
RSX-11M-Plus	O
with	O
hardware	O
autoconfiguration	O
,	O
implemented	O
specifically	O
for	O
the	O
Micro/PDP	O
-11s	O
,	O
a	O
low-cost	O
multi-user	B-Operating_System
system	I-Operating_System
in	O
a	O
box	O
,	O
featuring	O
ease	O
of	O
installation	O
,	O
no	O
system	B-Application
generation	I-Application
,	O
and	O
a	O
special	O
documentation	O
set	O
.	O
</s>
<s>
Later	O
superseded	O
by	O
RSX-11M	B-Application
Plus	O
.	O
</s>
<s>
Cloning	O
of	O
DEC	O
designs	O
began	O
in	O
1974	O
,	O
under	O
the	O
name	O
of	O
SM	B-Device
EVM	I-Device
(	O
or	O
)	O
.	O
</s>
<s>
As	O
happened	O
with	O
ES	B-Device
EVM	I-Device
mainframes	O
based	O
on	O
the	O
System/360	B-Application
architecture	O
,	O
the	O
Russians	O
and	O
their	O
allies	O
sometimes	O
significantly	O
modified	O
Western	O
designs	O
,	O
and	O
therefore	O
many	O
SM	B-Device
EVM	I-Device
machines	O
were	O
binary-incompatible	B-General_Concept
with	O
DEC	O
offerings	O
at	O
the	O
time	O
.	O
</s>
<s>
DOS/RV	O
,	O
,	O
ОСРВM	O
–	O
Three	O
names	O
for	O
an	O
unauthorised	O
clone	O
of	O
RSX-11M	B-Application
produced	O
in	O
the	O
Eastern	O
bloc	O
.	O
</s>
<s>
This	O
system	O
appears	O
to	O
be	O
an	O
exact	O
duplicate	O
of	O
RSX-11M	B-Application
except	O
a	O
different	O
header	O
in	O
binary	O
files	O
.	O
</s>
<s>
Differences	O
between	O
RSX	O
and	O
ОСРВ	O
are	O
due	O
to	O
hardware	O
differences	O
between	O
SM	B-Device
and	O
PDP	O
computers	O
and	O
to	O
bug-fixing	O
done	O
by	O
Soviet	O
engineers	O
.	O
</s>
<s>
However	O
,	O
the	O
original	O
RSX-11M	B-Application
was	O
more	O
used	O
than	O
its	O
Russian	O
clone	O
ОСРВ	O
,	O
because	O
the	O
programmers	O
modifying	O
the	O
original	O
RSX-11M	B-Application
code	O
were	O
doing	O
a	O
better	O
job	O
,	O
and	O
patched	O
RSX	O
was	O
more	O
stable	O
than	O
ОСРВ	O
.	O
</s>
<s>
A	O
clone	O
of	O
the	O
RSX-11M	B-Application
operating	B-General_Concept
system	I-General_Concept
ran	O
on	O
the	O
Romanian-made	O
CORAL	O
series	O
family	O
of	O
computers	O
(	O
such	O
as	O
CORAL	O
2030	O
,	O
a	O
clone	O
of	O
PDP-11	B-Device
)	O
.	O
</s>
<s>
RSX-11	B-Application
was	O
often	O
used	O
for	O
general-purpose	O
timeshare	O
computing	O
,	O
even	O
though	O
this	O
was	O
the	O
target	O
market	O
for	O
the	O
competing	O
RSTS/E	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
RSX-11	B-Application
provided	O
features	O
to	O
ensure	O
better	O
than	O
a	O
maximum	O
necessary	O
response	O
time	O
to	O
peripheral	O
device	O
input	O
(	O
i.e.	O
</s>
<s>
In	O
order	O
to	O
support	O
large	O
programs	O
within	O
the	O
PDP-11	B-Device
'	O
s	O
relatively	O
small	O
virtual	B-General_Concept
address	I-General_Concept
space	I-General_Concept
of	O
64KB	O
,	O
a	O
sophisticated	O
semi-automatic	O
overlay	B-General_Concept
system	I-General_Concept
was	O
used	O
;	O
for	O
any	O
given	O
program	O
,	O
this	O
overlay	B-General_Concept
scheme	O
was	O
produced	O
by	O
RSX	O
's	O
taskbuilder	O
program	O
(	O
called	O
TKB	O
)	O
.	O
</s>
<s>
If	O
the	O
overlay	B-General_Concept
scheme	O
was	O
especially	O
complex	O
,	O
taskbuilding	O
could	O
take	O
a	O
rather	O
long	O
time	O
(	O
hours	O
to	O
days	O
)	O
.	O
</s>
<s>
"	O
HELLO	O
"	O
was	O
chosen	O
as	O
the	O
login	O
command	O
because	O
only	O
the	O
first	O
three	O
characters	O
,	O
"	O
HEL	O
"	O
,	O
are	O
relevant	O
and	O
this	O
allows	O
a	O
non-logged	O
in	O
user	O
to	O
execute	O
a	O
"	O
HELP	B-Protocol
"	O
command	O
.	O
</s>
<s>
When	O
run	O
on	O
certain	O
PDP-11	B-Device
processors	O
,	O
each	O
DEC	O
operating	B-General_Concept
system	I-General_Concept
displays	O
a	O
characteristic	O
light	O
pattern	O
on	O
the	O
processor	O
console	O
panel	O
when	O
the	O
system	O
is	O
idle	O
.	O
</s>
<s>
The	O
RSX-11M	B-Application
light	O
pattern	O
is	O
two	O
sets	O
of	O
lights	O
that	O
sweep	O
outwards	O
to	O
the	O
left	O
and	O
right	O
from	O
the	O
center	O
of	O
the	O
console	O
(	O
inwards	O
if	O
the	O
IND	O
indirect	O
command	O
file	O
processor	O
program	O
was	O
currently	O
running	O
on	O
older	O
versions	O
of	O
RSX	O
)	O
.	O
</s>
<s>
By	O
contrast	O
,	O
the	O
IAS	B-Operating_System
light	O
pattern	O
was	O
a	O
single	O
bar	O
of	O
lights	O
that	O
swept	O
leftwards	O
.	O
</s>
<s>
Other	O
PDP-11	B-Device
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
RSTS/E	B-Operating_System
have	O
their	O
own	O
distinctive	O
patterns	O
in	O
the	O
console	O
lights	O
.	O
</s>
