<s>
RT-11	B-Operating_System
(	O
Real-time	O
11	O
)	O
is	O
a	O
discontinued	O
small	O
,	O
low-end	O
,	O
single-user	O
real-time	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
for	O
the	O
full	O
line	O
of	O
Digital	O
Equipment	O
Corporation	O
PDP-11	B-Device
16-bit	B-Device
computers	I-Device
.	O
</s>
<s>
RT-11	B-Operating_System
was	O
first	O
implemented	O
in	O
1970	O
.	O
</s>
<s>
It	O
was	O
widely	O
used	O
for	O
real-time	B-General_Concept
computing	I-General_Concept
systems	O
,	O
process	O
control	O
,	O
and	O
data	B-Algorithm
acquisition	I-Algorithm
across	O
all	O
PDP-11s	B-Device
.	O
</s>
<s>
RT-11	B-Operating_System
systems	O
did	O
not	O
support	O
preemptive	B-Operating_System
multitasking	I-Operating_System
,	O
but	O
most	O
versions	O
could	O
run	O
multiple	O
simultaneous	O
applications	O
.	O
</s>
<s>
The	O
FB	O
,	O
XM	O
,	O
and	O
ZM	O
monitors	O
also	O
provided	O
a	O
foreground	O
job	O
,	O
and	O
six	O
system	O
jobs	O
if	O
selected	O
via	O
the	O
SYSGEN	B-Application
system	B-Application
generation	I-Application
program	O
.	O
</s>
<s>
It	O
was	O
possible	O
to	O
switch	O
between	O
jobs	O
from	O
the	O
system	B-Device
console	I-Device
user	O
interface	O
,	O
and	O
SYSGEN	B-Application
could	O
generate	O
a	O
monitor	O
that	O
provided	O
a	O
single	O
background	O
job	O
(	O
the	O
SB	O
,	O
XB	O
and	O
ZB	O
variants	O
)	O
.	O
</s>
<s>
The	O
terms	O
foreground	O
and	O
background	O
are	O
counterintuitive	O
;	O
the	O
background	O
job	O
was	O
typically	O
the	O
user	O
's	O
command-line	B-Application
interpreter	I-Application
;	O
a	O
foreground	O
job	O
might	O
be	O
doing	O
something	O
like	O
non-interactive	O
data	O
collection	O
.	O
</s>
<s>
RT-11	B-Operating_System
was	O
written	O
in	O
assembly	B-Language
language	I-Language
.	O
</s>
<s>
Heavy	O
use	O
of	O
the	O
conditional	O
assembly	O
and	O
macro	O
programming	O
features	O
of	O
the	O
MACRO-11	B-Device
assembler	B-Language
allowed	O
a	O
significant	O
degree	O
of	O
configurability	O
and	O
allowed	O
programmers	O
to	O
specify	O
high-level	O
instructions	O
otherwise	O
unprovided	O
for	O
in	O
machine	O
code	O
.	O
</s>
<s>
RT-11	B-Operating_System
distributions	O
included	O
the	O
source	O
code	O
of	O
the	O
operating	O
system	O
and	O
its	O
device	B-Application
drivers	I-Application
with	O
all	O
the	O
comments	O
removed	O
and	O
a	O
program	O
named	O
"	O
SYSGEN	B-Application
"	O
which	O
would	O
build	O
the	O
operating	O
system	O
and	O
drivers	O
according	O
to	O
a	O
user-specified	O
configuration	O
.	O
</s>
<s>
Developer	O
's	O
documentation	O
included	O
a	O
kernel	B-Operating_System
listing	O
that	O
included	O
comments	O
.	O
</s>
<s>
In	O
RT-11	B-Operating_System
,	O
device	B-Application
drivers	I-Application
were	O
loadable	O
,	O
except	O
that	O
prior	O
to	O
V4.0	O
the	O
device	B-Application
driver	I-Application
for	O
the	O
system	O
device	O
(	O
boot	O
device	O
)	O
was	O
built	O
into	O
the	O
kernel	B-Operating_System
at	O
configuration	O
time	O
.	O
</s>
<s>
Because	O
RT-11	B-Operating_System
was	O
commonly	O
used	O
for	O
device	O
control	O
and	O
data	B-Algorithm
acquisition	I-Algorithm
,	O
it	O
was	O
common	O
for	O
developers	O
to	O
write	O
or	O
enhance	O
device	B-Application
drivers	I-Application
.	O
</s>
<s>
Users	O
generally	O
operated	O
RT-11	B-Operating_System
via	O
a	O
printing	O
terminal	B-Device
or	O
a	O
video	B-General_Concept
terminal	I-General_Concept
,	O
originally	O
via	O
a	O
strap-selectable	O
current-loop	O
(	O
for	O
conventional	O
teletypes	O
)	O
or	O
via	O
an	O
RS-232	O
(	O
later	O
RS-422	O
as	O
well	O
)	O
interface	O
on	O
one	O
of	O
the	O
CPU	O
cards	O
;	O
DEC	O
also	O
supported	O
the	O
VT11	O
and	O
VS60	O
graphics	O
display	O
devices	O
(	O
vector	O
graphics	O
terminals	O
with	O
a	O
graphic	O
character	O
generator	O
for	O
displaying	O
text	O
,	O
and	O
a	O
light	B-Device
pen	I-Device
for	O
graphical	O
input	O
)	O
.	O
</s>
<s>
A	O
third-party	O
favorite	O
was	O
the	O
Tektronix	B-General_Concept
4010	I-General_Concept
family	O
.	O
</s>
<s>
RT-11	B-Operating_System
command	O
language	O
had	O
many	O
features	O
(	O
such	O
as	O
commands	O
and	O
device	O
names	O
)	O
that	O
can	O
be	O
found	O
later	O
in	O
the	O
DOS	B-Device
line	O
of	O
operating	O
systems	O
which	O
heavily	O
borrowed	O
from	O
RT-11	B-Operating_System
.	O
</s>
<s>
The	O
CSI	O
form	O
expected	O
input	O
and	O
output	O
filenames	B-Device
and	O
options	O
( 	O
 '	O
switches	O
 '	O
on	O
RT-11	B-Operating_System
)	O
in	O
a	O
precise	O
order	O
and	O
syntax	O
.	O
</s>
<s>
The	O
command-line	B-Application
switches	O
were	O
separated	O
by	O
a	O
slash	O
(	O
/	O
)	O
rather	O
than	O
the	O
dash	O
(	O
-	O
)	O
used	O
in	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
For	O
example	O
,	O
the	O
RENAME	B-Device
command	O
could	O
be	O
contracted	O
to	O
REN	B-Device
.	O
</s>
<s>
In	O
later	O
releases	O
of	O
RT-11	B-Operating_System
,	O
it	O
was	O
possible	O
to	O
invoke	O
a	O
series	O
of	O
commands	O
using	O
a	O
.COM	O
command	O
file	O
,	O
but	O
they	O
would	O
be	O
executed	O
in	O
sequence	O
with	O
no	O
flow	O
control	O
.	O
</s>
<s>
They	O
were	O
known	O
as	O
"	O
save	O
files	O
"	O
because	O
the	O
RT-11	B-Operating_System
SAVE	O
command	O
could	O
be	O
used	O
to	O
save	O
the	O
contents	O
of	O
memory	O
to	O
a	O
disk	O
file	O
which	O
could	O
be	O
loaded	O
and	O
executed	O
at	O
a	O
later	O
time	O
,	O
allowing	O
any	O
session	O
to	O
be	O
saved	O
.	O
</s>
<s>
Some	O
commands	O
and	O
utilities	O
were	O
later	O
borrowed	O
in	O
the	O
DOS	B-Device
line	O
of	O
operating	O
systems	O
.	O
</s>
<s>
These	O
commands	O
include	O
DIR	B-Device
,	O
COPY	B-Device
,	O
RENAME	B-Device
,	O
ASSIGN	O
,	O
CLS	O
,	O
DELETE	B-Device
,	O
TYPE	B-Device
,	O
HELP	B-Protocol
and	O
others	O
.	O
</s>
<s>
The	O
FORMAT	B-Application
command	O
was	O
used	O
for	O
physical	O
disk	O
formatting	O
,	O
although	O
it	O
was	O
not	O
capable	O
of	O
creating	O
file	B-Application
system	I-Application
,	O
for	O
which	O
purpose	O
the	O
INIT	O
command	O
was	O
used	O
(	O
analogue	O
of	O
DOS	B-Device
command	O
FORMAT	B-Application
/Q	O
)	O
.	O
</s>
<s>
Most	O
commands	O
supported	O
using	O
wildcards	B-Algorithm
in	O
file	O
names	O
.	O
</s>
<s>
For	O
example	O
,	O
TT	O
:	O
referred	O
to	O
the	O
console	B-General_Concept
terminal	I-General_Concept
,	O
LP	O
:	O
(	O
or	O
LP0	O
:	O
)	O
referred	O
to	O
the	O
parallel	O
line	O
printer	O
,	O
and	O
DX0	O
:	O
,	O
DY1	O
:	O
,	O
DL4	O
:	O
referred	O
to	O
disk	O
volumes	O
(	O
RX01	O
unit	O
0	O
,	O
RX02	O
unit	O
1	O
,	O
RL01	O
or	O
RL02	O
unit	O
4	O
,	O
respectively	O
)	O
.	O
</s>
<s>
Later	O
versions	O
of	O
RT-11	B-Operating_System
allowed	O
specification	O
of	O
up	O
to	O
64	O
units	O
(	O
0	O
–	O
77	O
octal	O
)	O
for	O
certain	O
devices	O
,	O
but	O
the	O
device	O
name	O
was	O
still	O
limited	O
to	O
three	O
alphanumeric	O
characters	O
.	O
</s>
<s>
This	O
feature	O
was	O
enabled	O
through	O
a	O
SYSGEN	B-Application
selection	O
,	O
and	O
only	O
applied	O
to	O
the	O
DU	O
and	O
LD	O
device	O
handlers	O
.	O
</s>
<s>
RT-11	B-Operating_System
was	O
distributed	O
with	O
utilities	O
for	O
performimg	O
many	O
actions	O
.	O
</s>
<s>
The	O
utilities	O
DIR	B-Device
,	O
DUP	O
,	O
PIP	B-Application
and	O
FORMAT	B-Application
were	O
for	O
managing	O
disk	O
volumes	O
.	O
</s>
<s>
TECO	B-Application
,	O
EDIT	O
,	O
and	O
the	O
visual	B-Application
editors	I-Application
KED	O
(	O
for	O
the	O
DEC	B-Device
VT100	I-Device
)	O
and	O
K52	O
(	O
for	O
the	O
DEC	O
VT52	B-Application
)	O
were	O
used	O
to	O
create	O
and	O
edit	O
source	O
and	O
data	O
files	O
.	O
</s>
<s>
ODT	B-Application
,	O
VDT	O
and	O
the	O
SD	O
device	O
were	O
used	O
to	O
debug	O
programs	O
.	O
</s>
<s>
DEC	O
's	O
version	O
of	O
Runoff	B-Protocol
was	O
for	O
producing	O
documents	O
.	O
</s>
<s>
Productivity	O
software	O
such	O
as	O
LEX-11	O
,	O
a	O
word	O
processing	O
package	O
,	O
and	O
a	O
spreadsheet	O
from	O
Saturn	O
Software	O
,	O
used	O
under	O
other	O
PDP-11	B-Device
operating	O
systems	O
,	O
also	O
ran	O
on	O
RT-11	B-Operating_System
.	O
</s>
<s>
Large	O
amounts	O
of	O
free	O
,	O
user-contributed	O
software	O
for	O
RT-11	B-Operating_System
were	O
available	O
from	O
the	O
Digital	O
Equipment	O
Computer	O
Users	O
Society	O
(	O
DECUS	O
)	O
including	O
an	O
implementation	O
of	O
C	B-Language
.	O
Although	O
the	O
tools	O
to	O
develop	O
and	O
debug	O
assembly-language	O
programs	O
were	O
provided	O
,	O
other	O
languages	O
including	O
C	B-Language
,	O
Fortran	B-Application
,	O
Pascal	B-Application
,	O
and	O
several	O
versions	O
of	O
BASIC	O
were	O
available	O
from	O
DEC	O
as	O
"	O
layered	O
products	O
"	O
at	O
extra	O
cost	O
.	O
</s>
<s>
It	O
is	O
even	O
possible	O
to	O
network	O
RT-11	B-Operating_System
machines	O
using	O
DECNET	B-Protocol
,	O
the	O
Internet	B-Protocol
and	O
protocols	O
developed	O
by	O
other	O
,	O
third-party	O
sources	O
.	O
</s>
<s>
The	O
RT-11	B-Operating_System
operating	O
system	O
could	O
be	O
booted	O
from	O
,	O
and	O
perform	O
useful	O
work	O
on	O
,	O
a	O
machine	O
consisting	O
of	O
two	O
8-inch	O
250KB	O
floppy	B-Device
disks	I-Device
and	O
56KB	O
of	O
memory	O
,	O
and	O
could	O
support	O
8	O
terminals	O
.	O
</s>
<s>
Other	O
boot	O
options	O
include	O
the	O
RK05	B-Device
2.5MB	O
removable	O
hard	O
disk	O
platter	O
,	O
or	O
magnetic	O
tape	O
.	O
</s>
<s>
Distributions	O
were	O
available	O
pre-installed	O
or	O
on	O
punched	O
tape	O
,	O
magnetic	O
tape	O
,	O
cartridge	O
tape	O
,	O
or	O
floppy	B-Device
disk	I-Device
.	O
</s>
<s>
A	O
minimal	O
but	O
complete	O
system	O
supporting	O
a	O
single	O
real-time	O
user	O
could	O
run	O
on	O
a	O
single	O
floppy	B-Device
disk	I-Device
and	O
in	O
8K	O
16-bit	B-Device
words	O
(	O
16KB	O
)	O
of	O
RAM	O
,	O
including	O
user	O
programs	O
.	O
</s>
<s>
The	O
system	O
supported	O
a	O
real-time	O
clock	O
,	O
printing	O
terminal	B-Device
,	O
VT11	O
vector	O
graphic	O
unit	O
,	O
16	O
channel	O
100kHz	O
A/D	O
converter	O
with	O
2	O
channel	O
D/A	O
,	O
9600	O
baud	O
serial	O
port	O
,	O
16	B-Device
bit	I-Device
bidirectional	O
boards	O
,	O
etc	O
.	O
</s>
<s>
RT-11	B-Operating_System
implemented	O
a	O
simple	O
and	O
fast	O
file	B-Application
system	I-Application
employing	O
six-character	O
filenames	B-Device
with	O
three-character	O
extensions	O
(	O
6.3	O
)	O
encoded	O
in	O
RADIX-50	O
,	O
which	O
packed	O
those	O
nine	O
characters	O
into	O
only	O
three	O
16-bit	B-Device
words	O
(	O
six	O
bytes	O
)	O
.	O
</s>
<s>
A	O
side	O
effect	O
of	O
this	O
file	B-Application
system	I-Application
structure	O
was	O
that	O
,	O
as	O
files	O
were	O
created	O
and	O
deleted	O
on	O
a	O
volume	O
over	O
time	O
,	O
the	O
unused	O
disk	O
blocks	O
would	O
likely	O
not	O
remain	O
contiguous	O
,	O
which	O
could	O
become	O
the	O
limiting	O
factor	O
in	O
creating	O
large	O
files	O
;	O
the	O
remedy	O
was	O
to	O
periodically	O
“	O
squeeze	O
”	O
(	O
or	O
"	O
squish	O
"	O
)	O
a	O
disk	O
to	O
consolidate	O
the	O
unused	O
portions	O
.	O
</s>
<s>
Each	O
directory	O
entry	O
is	O
8	O
(	O
or	O
more	O
)	O
16-bit	B-Device
words	O
,	O
though	O
a	O
sysgen	B-Application
option	O
allowed	O
extra	O
application-specific	O
storage	O
.	O
</s>
<s>
Many	O
RT-11	B-Operating_System
programs	O
(	O
those	O
that	O
did	O
not	O
need	O
specialized	O
peripherals	O
or	O
direct	O
access	O
to	O
the	O
hardware	O
)	O
could	O
be	O
directly	O
executed	O
using	O
the	O
RT	O
=	O
11	O
RTS	O
(	O
Run-time	B-Device
system	I-Device
)	O
of	O
the	O
RSTS/E	B-Operating_System
timesharing	O
system	O
or	O
under	O
RTEM	O
(	O
RT	O
Emulator	O
)	O
on	O
various	O
releases	O
of	O
both	O
RSX-11	B-Application
and	O
VMS	B-Operating_System
.	O
</s>
<s>
The	O
implementation	O
of	O
DCL	B-Operating_System
for	O
RT-11	B-Operating_System
increased	O
its	O
compatibility	O
with	O
the	O
other	O
DEC	O
operating	O
systems	O
.	O
</s>
<s>
DEC	O
also	O
sold	O
RSX-11	B-Application
,	O
a	O
multiuser	O
,	O
multitasking	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
with	O
realtime	O
features	O
,	O
and	O
RSTS/E	B-Operating_System
(	O
originally	O
named	O
RSTS-11	B-Operating_System
)	O
a	O
multiuser	O
time-sharing	O
system	O
,	O
but	O
RT-11	B-Operating_System
remained	O
the	O
operating	O
system	O
of	O
choice	O
for	O
data	B-Algorithm
acquisition	I-Algorithm
systems	I-Algorithm
where	O
real	O
time	O
response	O
was	O
required	O
.	O
</s>
<s>
The	O
Unix	B-Application
operating	I-Application
system	I-Application
also	O
became	O
popular	O
,	O
but	O
lacked	O
the	O
real-time	O
features	O
and	O
extremely	O
small	O
size	O
of	O
RT-11	B-Operating_System
.	O
</s>
<s>
RT-11	B-Operating_System
ran	O
on	O
all	O
members	O
of	O
the	O
DEC	B-Device
PDP-11	I-Device
family	O
,	O
both	O
Q-Bus	B-Architecture
-	O
and	O
Unibus-based	O
,	O
from	O
the	O
PDP-11/05	O
(	O
its	O
first	O
target	O
,	O
in	O
1970	O
(	O
note	O
that	O
the	O
PDP-11/05	O
was	O
released	O
1972	O
,	O
so	O
this	O
probably	O
was	O
a	O
PDP-11/20	O
)	O
)	O
,	O
to	O
the	O
final	O
PDP-11	B-Device
implementations	O
(	O
PDP-11/93	O
and	O
/94	O
)	O
.	O
</s>
<s>
In	O
addition	O
,	O
it	O
ran	O
on	O
the	O
Professional	O
Series	O
and	O
the	O
PDT-11	O
"	O
Programmed	O
Data	B-General_Concept
Terminal	I-General_Concept
"	O
systems	O
,	O
also	O
from	O
DEC	O
.	O
</s>
<s>
Since	O
the	O
PDP-11	B-Device
architecture	O
was	O
implemented	O
in	O
replacement	O
products	O
by	O
other	O
companies	O
(	O
E.g.	O
,	O
the	O
M100	O
and	O
family	O
from	O
Mentec	O
)	O
,	O
or	O
as	O
reverse-engineered	O
clones	O
in	O
other	O
countries	O
(	O
E.g.	O
,	O
the	O
DVK	B-Device
from	O
the	O
Soviet	O
Union	O
)	O
,	O
RT-11	B-Operating_System
runs	O
on	O
these	O
machines	O
as	O
well	O
.	O
</s>
<s>
Adding	O
driver	O
support	O
for	O
peripherals	O
such	O
as	O
a	O
CalComp	O
plotter	O
,	O
typically	O
involved	O
copying	O
files	O
,	O
and	O
did	O
not	O
require	O
a	O
SYSGEN	B-Application
.	O
</s>
<s>
Fuzzball	B-Protocol
,	O
routing	O
software	O
for	O
Internet	B-Protocol
Protocols	I-Protocol
,	O
was	O
capable	O
of	O
running	O
RT-11	B-Operating_System
programs	O
.	O
</s>
<s>
HAMMONDsoftware	O
distributed	O
a	O
number	O
of	O
RT-11	B-Operating_System
compatible	O
operating	O
systems	O
including	O
STAReleven	O
,	O
an	O
early	O
multi-computer	O
system	O
and	O
SHAREplus	O
,	O
a	O
multi-process/multi	O
-user	O
implementation	O
of	O
RT-11	B-Operating_System
which	O
borrowed	O
some	O
architectural	O
concepts	O
from	O
the	O
VAX/VMS	B-Operating_System
operating	O
system	O
.	O
</s>
<s>
RT-11	B-Operating_System
device	B-Application
drivers	I-Application
were	O
required	O
for	O
operation	O
.	O
</s>
<s>
Transparent	O
device	O
access	O
to	O
other	O
PDP-11s	B-Device
and	O
VAX/VMS	B-Operating_System
were	O
supported	O
with	O
a	O
network	O
option	O
.	O
</s>
<s>
Limited	O
RSX-11	B-Application
application	O
compatibility	O
was	O
also	O
available	O
.	O
</s>
<s>
TSX-11	O
,	O
developed	O
by	O
S&H	O
Computing	O
,	O
was	O
a	O
multi-user	O
,	O
multi-processing	O
implementation	O
of	O
RT-11	B-Operating_System
.	O
</s>
<s>
The	O
only	O
thing	O
it	O
did	O
n't	O
do	O
was	O
handle	O
the	O
boot	O
process	O
,	O
so	O
any	O
TSX-Plus	O
machine	O
was	O
required	O
to	O
boot	O
RT-11	B-Operating_System
first	O
before	O
running	O
TSX-Plus	O
as	O
a	O
user	O
program	O
.	O
</s>
<s>
Once	O
TSX-Plus	O
was	O
running	O
,	O
it	O
would	O
take	O
over	O
complete	O
control	O
of	O
the	O
machine	O
from	O
RT-11	B-Operating_System
.	O
</s>
<s>
It	O
provided	O
true	O
memory	O
protection	O
for	O
users	O
from	O
other	O
users	O
,	O
provided	O
user	O
accounts	O
and	O
maintained	O
account	O
separation	O
on	O
disk	O
volumes	O
and	O
implemented	O
a	O
superset	O
of	O
the	O
RT-11	B-Operating_System
EMT	O
programmed	O
requests	O
.	O
</s>
<s>
RT-11	B-Operating_System
programs	O
generally	O
ran	O
,	O
unmodified	O
,	O
under	O
TSX-Plus	O
and	O
,	O
in	O
fact	O
,	O
most	O
of	O
the	O
RT-11	B-Operating_System
utilities	O
were	O
used	O
as-is	O
under	O
TSX-Plus	O
.	O
</s>
<s>
Device	B-Application
drivers	I-Application
generally	O
required	O
only	O
slight	O
modifications	O
.	O
</s>
<s>
Depending	O
on	O
which	O
PDP-11	B-Device
model	O
and	O
the	O
amount	O
of	O
memory	O
,	O
the	O
system	O
could	O
support	O
a	O
minimum	O
of	O
12	O
users	O
(	O
14-18	O
users	O
on	O
a	O
2Mb	O
11/73	O
,	O
depending	O
on	O
workload	O
)	O
.	O
</s>
<s>
The	O
last	O
version	O
of	O
TSX-Plus	O
had	O
TCP/IP	B-Protocol
support	O
.	O
</s>
<s>
Users	O
could	O
choose	O
from	O
variants	O
with	O
differing	O
levels	O
of	O
support	O
for	O
multitasking	B-Operating_System
,	O
memory	O
size	O
,	O
and	O
separate	O
I	O
&	O
D	O
(	O
Instruction	O
and	O
Data	O
)	O
address	O
space	O
:	O
</s>
<s>
RT-11ZM	O
provided	O
support	O
for	O
systems	O
with	O
Separate	O
Instruction	O
and	O
Data	O
space	O
(	O
such	O
as	O
on	O
the	O
Unibus-based	O
11/44	O
,	O
45	O
,	O
55	O
,	O
70	O
,	O
84	O
,	O
and	O
94	O
and	O
the	O
Q-Bus-based	O
11/53	O
,	O
73	B-Device
,	O
83	O
,	O
and	O
93	O
.	O
)	O
</s>
<s>
Several	O
specialized	O
PDP-11	B-Device
systems	O
were	O
sold	O
based	O
on	O
RT-11	B-Operating_System
:	O
</s>
<s>
PEAK-11	O
provided	O
further	O
customization	O
for	O
use	O
with	O
gas	O
chromatographs	O
(	O
analyzing	O
the	O
peaks	O
produced	O
by	O
the	O
GC	O
)	O
;	O
data	O
collection	O
ran	O
in	O
RT-11	B-Operating_System
'	O
s	O
foreground	O
process	O
while	O
the	O
user	O
's	O
data	O
analysis	O
programs	O
ran	O
in	O
the	O
background	O
.	O
</s>
<s>
Several	O
very	O
popular	O
demo	O
programs	O
were	O
provided	O
with	O
these	O
systems	O
including	O
Lunar	B-Application
Lander	I-Application
and	O
a	O
version	O
of	O
Spacewar	B-Application
!	I-Application
.	O
</s>
<s>
GAMMA-11	O
was	O
a	O
packaged	O
RT-11	B-Operating_System
and	O
PDP	O
11/34	O
system	O
that	O
was	O
one	O
of	O
the	O
first	O
fully	O
integrated	O
Nuclear	O
Medicine	O
systems	O
.	O
</s>
<s>
It	O
included	O
fast	O
analog/digital	O
converters	O
,	O
16	B-Device
bit	I-Device
colour	O
graphical	O
displays	O
,	O
and	O
an	O
extensive	O
software	O
library	O
for	O
development	O
of	O
applications	O
for	O
the	O
purpose	O
of	O
data	O
collection	O
,	O
analysis	O
and	O
display	O
from	O
a	O
nuclear	O
medicine	O
gamma	O
camera	O
.	O
</s>
<s>
Several	O
clones	O
of	O
RT-11	B-Operating_System
were	O
made	O
in	O
the	O
USSR	O
:	O
</s>
