<s>
RSTS	B-Operating_System
(	O
)	O
is	O
a	O
multi-user	B-Operating_System
time-sharing	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
developed	O
by	O
Digital	O
Equipment	O
Corporation	O
(	O
DEC	O
,	O
now	O
part	O
of	O
Hewlett-Packard	O
)	O
for	O
the	O
PDP-11	B-Device
series	O
of	O
16-bit	B-Device
minicomputers	B-Architecture
.	O
</s>
<s>
The	O
first	O
version	O
of	O
RSTS	B-Operating_System
(	O
RSTS-11	B-Operating_System
,	O
Version	O
1	O
)	O
was	O
implemented	O
in	O
1970	O
by	O
DEC	O
software	B-General_Concept
engineers	I-General_Concept
that	O
developed	O
the	O
TSS-8	B-Operating_System
time-sharing	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
for	O
the	O
PDP-8	B-Device
.	O
</s>
<s>
The	O
last	O
version	O
of	O
RSTS	B-Operating_System
(	O
RSTS/E	B-Operating_System
,	O
Version	O
10.1	O
)	O
was	O
released	O
in	O
September	O
1992	O
.	O
</s>
<s>
RSTS-11	B-Operating_System
and	O
RSTS/E	B-Operating_System
are	O
usually	O
referred	O
to	O
just	O
as	O
"	O
RSTS	B-Operating_System
"	O
and	O
this	O
article	O
will	O
generally	O
use	O
the	O
shorter	O
form	O
.	O
</s>
<s>
RSTS-11	B-Operating_System
supports	O
the	O
BASIC	O
programming	O
language	O
,	O
an	O
extended	O
version	O
called	O
BASIC-PLUS	B-Language
,	O
developed	O
under	O
contract	O
by	O
Evans	O
Griffiths	O
&	O
Hart	O
of	O
Boston	O
.	O
</s>
<s>
Starting	O
with	O
RSTS/E	B-Operating_System
version	O
5B	O
,	O
DEC	O
added	O
support	O
for	O
additional	O
programming	O
languages	O
by	O
emulating	O
the	O
execution	O
environment	O
of	O
the	O
RT-11	B-Operating_System
and	O
RSX-11	B-Application
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
BTSS	O
(	O
Basic	O
Time	B-General_Concept
Sharing	I-General_Concept
System	O
–	O
never	O
marketed	O
)	O
–	O
The	O
first	O
name	O
for	O
RSTS	B-Operating_System
.	O
</s>
<s>
CCL	B-Operating_System
(	O
Concise	B-Operating_System
Command	I-Operating_System
Language	I-Operating_System
)	O
–	O
equivalent	O
to	O
a	O
command	O
to	O
run	O
a	O
program	B-Application
kept	O
in	O
the	O
Command	B-Application
Line	I-Application
Interpreter	O
.	O
</s>
<s>
CIL	O
(	O
Core	O
Image	O
Library	O
)	O
–	O
A	O
container	O
file	O
format	O
used	O
to	O
hold	O
one	O
or	O
more	O
standalone	O
(	O
bootable	B-Operating_System
)	O
programs	O
and	O
operating	B-General_Concept
systems	I-General_Concept
,	O
such	O
as	O
RSTS	B-Operating_System
through	O
version	O
6A	O
.	O
</s>
<s>
CILUS	B-Operating_System
(	O
Core	O
Image	O
Library	O
Update	O
and	O
Save	O
)	O
–	O
DOS-11	B-Operating_System
program	B-Application
to	O
manipulate	O
a	O
CIL	O
file	O
.	O
</s>
<s>
CLI	O
(	O
Command	B-Application
Line	I-Application
Interpreter	O
)	O
–	O
See	O
Command-line	B-Application
interface	I-Application
.	O
</s>
<s>
CUSPs	O
(	O
Commonly	O
Used	O
System	O
Programs	O
)	O
–	O
System	O
management	O
applications	O
like	O
Task	B-General_Concept
Manager	I-General_Concept
or	O
Registry	B-Protocol
Editor	I-Protocol
on	O
Microsoft	B-Application
Windows	I-Application
.	O
</s>
<s>
On	O
RSTS-11	B-Operating_System
,	O
CUSPs	O
were	O
written	O
in	O
BASIC-Plus	B-Language
just	O
like	O
user	O
programs	O
.	O
</s>
<s>
DCL	B-Operating_System
(	O
Digital	B-Operating_System
Command	I-Operating_System
Language	I-Operating_System
)	O
–	O
See	O
DIGITAL	B-Operating_System
Command	I-Operating_System
Language	I-Operating_System
.	O
</s>
<s>
KBM	O
(	O
Keyboard	O
Monitor	O
)	O
–	O
Analogous	O
to	O
Command	B-Application
Line	I-Application
Interpreter	O
.	O
</s>
<s>
PPN	O
(	O
Project	O
Programmer	O
Number	O
)	O
–	O
Analogous	O
to	O
GID	B-Application
and	O
UID	B-Application
in	O
Unix	B-Application
.	O
</s>
<s>
RDC	O
(	O
Remote	O
Diagnostics	O
Console	O
)	O
–	O
A	O
replacement	O
front	B-Device
panel	I-Device
for	O
a	O
PDP-11	B-Device
which	O
used	O
a	O
serial	O
connection	O
to	O
the	O
console	B-General_Concept
terminal	I-General_Concept
or	O
a	O
modem	B-Application
instead	O
of	O
lights	O
and	O
toggle	O
switches	O
to	O
control	O
the	O
CPU	O
.	O
</s>
<s>
RSTS/E	B-Operating_System
(	O
Resource	O
Sharing	O
Timesharing	B-General_Concept
System	O
Extended	O
)	O
–	O
The	O
current	O
implementation	O
of	O
RSTS	B-Operating_System
.	O
</s>
<s>
RTS	B-Device
(	O
Run	B-Device
Time	I-Device
System	I-Device
)	O
–	O
Read	O
only	O
segment	O
of	O
code	O
provided	O
by	O
the	O
supplier	O
which	O
would	O
be	O
mapped	O
into	O
the	O
high	O
end	O
of	O
a	O
32K	O
,	O
16-bit	B-Device
word	O
address	O
space	O
that	O
a	O
user	O
program	B-Application
would	O
use	O
to	O
interface	O
with	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Only	O
one	O
copy	O
of	O
an	O
RTS	B-Device
would	O
be	O
loaded	O
into	O
RAM	O
,	O
but	O
would	O
be	O
mapped	O
into	O
the	O
address	O
space	O
of	O
any	O
user	O
program	B-Application
that	O
required	O
it	O
.	O
</s>
<s>
SATT	O
(	O
Storage	O
Allocation	O
Truth	O
Table	O
)	O
a	O
series	O
of	O
512KB	O
blocks	O
on	O
every	O
disk	B-Device
that	O
indicated	O
if	O
the	O
block	O
,	O
or	O
cluster	O
,	O
on	O
the	O
whole	O
disk	B-Device
was	O
allocated	O
on	O
the	O
disk	B-Device
.	O
</s>
<s>
SIL	O
(	O
Save	O
Image	O
Library	O
)	O
–	O
The	O
OS	O
container	O
file	O
format	O
after	O
the	O
RSTS	B-Operating_System
system	B-Application
generation	I-Application
procedure	O
was	O
switched	O
from	O
one	O
using	O
DOS-11	B-Operating_System
to	O
one	O
running	O
natively	O
on	O
RSTS/E	B-Operating_System
,	O
called	O
that	O
by	O
analogy	O
to	O
the	O
CIL	O
it	O
replaced	O
.	O
</s>
<s>
SILUS	O
(	O
Save	O
Image	O
Library	O
Update	O
and	O
Save	O
)	O
–	O
The	O
program	B-Application
to	O
create	O
SIL	O
files	O
,	O
called	O
that	O
by	O
analogy	O
to	O
the	O
(	O
unrelated	O
)	O
DOS-11	B-Operating_System
CILUS	B-Operating_System
program	B-Application
it	O
replaced	O
.	O
</s>
<s>
The	O
kernel	B-Operating_System
of	O
RSTS	B-Operating_System
was	O
programmed	B-General_Concept
in	O
the	O
assembly	B-Language
language	I-Language
MACRO-11	B-Device
,	O
compiled	B-Language
and	O
installed	B-Application
to	O
a	O
disk	B-Device
using	O
the	O
CILUS	B-Operating_System
program	B-Application
,	O
running	O
on	O
a	O
DOS-11	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
RSTS	B-Operating_System
booted	B-Operating_System
into	O
an	O
extended	O
version	O
of	O
the	O
BASIC	O
programming	O
language	O
which	O
DEC	O
called	O
"	O
BASIC-PLUS	B-Language
"	O
.	O
</s>
<s>
All	O
of	O
the	O
system	B-Application
software	I-Application
CUSPS	O
for	O
the	O
operating	B-General_Concept
system	I-General_Concept
,	O
including	O
the	O
programs	O
for	O
resource	O
accounting	O
,	O
login	B-General_Concept
,	O
logout	O
,	O
and	O
managing	O
the	O
system	O
,	O
were	O
written	O
in	O
BASIC-PLUS	B-Language
.	O
</s>
<s>
From	O
1970	O
to	O
1973	O
,	O
RSTS	B-Operating_System
ran	O
in	O
only	O
56K	O
bytes	B-Application
of	O
magnetic	O
core	O
memory	O
(	O
64	O
kilobytes	O
including	O
the	O
memory-mapped	B-Architecture
I/O	I-Architecture
space	O
)	O
.	O
</s>
<s>
The	O
maximum	O
program	B-Application
size	O
was	O
16K	O
bytes	B-Application
.	O
</s>
<s>
By	O
the	O
end	O
of	O
1973	O
DEC	O
estimated	O
there	O
were	O
150	O
licensed	O
systems	O
running	O
RSTS	B-Operating_System
.	O
</s>
<s>
In	O
1973	O
memory	B-General_Concept
management	I-General_Concept
support	O
was	O
included	O
in	O
RSTS	B-Operating_System
(	O
now	O
RSTS/E	B-Operating_System
)	O
for	O
the	O
newer	O
DEC	O
PDP-11/40	O
and	O
PDP-11/45	B-Device
minicomputers	B-Architecture
(	O
the	O
PDP-11/20	O
was	O
only	O
supported	O
under	O
RSTS-11	B-Operating_System
)	O
.	O
</s>
<s>
The	O
introduction	O
of	O
memory	B-General_Concept
management	I-General_Concept
in	O
the	O
newer	O
PDP-11	B-Device
computers	O
not	O
only	O
meant	O
these	O
machines	O
were	O
able	O
to	O
address	O
four	O
times	O
the	O
amount	O
of	O
memory	O
(	O
18-bit	O
addressing	O
,	O
256K	O
bytes	B-Application
)	O
,	O
it	O
also	O
paved	O
the	O
way	O
for	O
the	O
developers	O
to	O
separate	O
user	B-Operating_System
mode	I-Operating_System
processes	O
from	O
the	O
core	O
of	O
the	O
kernel	B-Operating_System
.	O
</s>
<s>
In	O
1975	O
memory	B-General_Concept
management	I-General_Concept
support	O
was	O
again	O
updated	O
for	O
the	O
newer	O
22-bit	O
addressable	O
PDP-11/70	B-Device
.	O
</s>
<s>
RSTS	B-Operating_System
systems	O
could	O
now	O
be	O
expanded	O
to	O
use	O
as	O
much	O
as	O
two	O
megabytes	O
of	O
memory	O
running	O
up	O
to	O
63	O
jobs	O
.	O
</s>
<s>
The	O
RTS	B-Device
and	O
CCL	B-Operating_System
concepts	O
were	O
introduced	O
although	O
they	O
had	O
to	O
be	O
compiled	B-Language
in	O
during	O
"	O
SYSGEN	B-Application
"	O
.	O
</s>
<s>
Multi-terminal	O
service	O
was	O
introduced	O
which	O
would	O
allow	O
a	O
single	O
job	O
the	O
ability	O
to	O
control	O
multiple	O
terminals	O
(	O
128	O
total	O
)	O
.	O
</s>
<s>
In	O
1977	O
the	O
installation	B-Application
process	O
for	O
RSTS	B-Operating_System
was	O
no	O
longer	O
dependent	O
on	O
DOS-11	B-Operating_System
.	O
</s>
<s>
The	O
RSTS	B-Operating_System
kernel	B-Operating_System
could	O
now	O
be	O
compiled	B-Language
under	O
the	O
RT-11	B-Operating_System
RTS	B-Device
,	O
formatted	O
as	O
a	O
kernel	B-Operating_System
file	O
with	O
RT-11	B-Operating_System
SILUS	O
,	O
and	O
copied	O
to	O
the	O
system	O
or	O
other	O
disks	O
,	O
while	O
the	O
computer	O
was	O
time-sharing	B-General_Concept
.	O
</s>
<s>
The	O
BASIC-PLUS	B-Language
RTS	B-Device
(	O
as	O
well	O
as	O
RT-11	B-Operating_System
,	O
RSX-11	B-Application
,	O
TECO	B-Application
and	O
third	O
party	O
RTSs	O
)	O
all	O
ran	O
as	O
user	B-Operating_System
mode	I-Operating_System
processes	O
,	O
independent	O
of	O
the	O
RSTS	B-Operating_System
kernel	B-Operating_System
.	O
</s>
<s>
A	O
systems	B-Application
manager	I-Application
could	O
now	O
decide	O
during	O
the	O
bootstrap	O
phase	O
which	O
RTS	B-Device
to	O
run	O
as	O
the	O
systems	O
default	O
Keyboard	O
Monitor	O
(	O
KBM	O
)	O
.	O
</s>
<s>
In	O
1978	O
the	O
final	O
memory	B-General_Concept
management	I-General_Concept
update	O
was	O
included	O
for	O
all	O
machines	O
that	O
could	O
support	O
22-bit	O
addressing	O
.	O
</s>
<s>
RSTS	B-Operating_System
could	O
now	O
use	O
the	O
maximum	O
amount	O
of	O
memory	O
available	O
to	O
a	O
PDP-11	B-Device
(	O
4	O
megabytes	O
)	O
.	O
</s>
<s>
Support	O
was	O
also	O
included	O
for	O
SUPERVISORY	O
mode	O
which	O
made	O
RSTS	B-Operating_System
the	O
first	O
DEC	O
operating	B-General_Concept
system	I-General_Concept
with	O
this	O
capability	O
.	O
</s>
<s>
DECnet	B-Protocol
was	O
also	O
supported	O
as	O
well	O
as	O
remote	O
diagnostics	O
from	O
field	O
service	O
technicians	O
at	O
the	O
RDC	O
in	O
Colorado	O
Springs	O
,	O
Colorado	O
(	O
a	O
DEC	O
subscription	O
service	O
)	O
.	O
</s>
<s>
In	O
1981	O
support	O
for	O
separate	O
instruction	O
and	O
data	O
space	O
for	O
users	O
with	O
Unibus	B-Device
machines	O
(	O
PDP-11/44	B-Device
,	O
PDP-11/45	B-Device
,	O
PDP-11/55	O
and	O
PDP-11/70	B-Device
)	O
provided	O
an	O
extension	O
to	O
the	O
memory	O
constraints	O
of	O
an	O
individual	O
program	B-Application
.	O
</s>
<s>
Compiling	B-Language
programs	O
to	O
use	O
separate	O
instruction	O
and	O
data	O
space	O
would	O
soon	O
give	O
a	O
program	B-Application
up	O
to	O
64KiB	O
for	O
instructions	O
,	O
and	O
up	O
to	O
64KiB	O
for	O
buffering	O
data	O
.	O
</s>
<s>
The	O
DCL	B-Operating_System
RTS	B-Device
was	O
included	O
as	O
well	O
as	O
support	O
for	O
the	O
newer	O
revision	O
of	O
DECnet	B-Protocol
III	O
.	O
</s>
<s>
By	O
1983	O
,	O
with	O
an	O
estimated	O
15,000	O
DEC	O
machines	O
running	O
RSTS/E	B-Operating_System
,	O
V8.0-06	O
included	O
support	O
for	O
the	O
smallest	O
18-bit	O
PDP-11	B-Device
sold	O
by	O
DEC	O
(	O
the	O
MicroPDP-11	O
)	O
.	O
</s>
<s>
A	O
pre-generated	O
kernel	B-Operating_System
and	O
CUSPS	O
were	O
included	O
in	O
this	O
distribution	O
to	O
make	O
installation	B-Application
on	O
the	O
MicroPDP-11	O
easier	O
.	O
</s>
<s>
DEC	O
sold	O
the	O
pre-generated	O
version	O
on	O
the	O
MicroPDP-11	O
as	O
MicroRSTS	O
at	O
a	O
reduced	O
price	O
,	O
however	O
users	O
needed	O
to	O
purchase	O
the	O
full	O
version	O
if	O
they	O
had	O
a	O
need	O
to	O
generate	O
their	O
own	O
kernel	B-Operating_System
.	O
</s>
<s>
The	O
file	O
system	O
was	O
upgraded	O
and	O
given	O
the	O
designation	O
RSTS	B-Operating_System
Directory	O
Structure	O
1	O
(	O
RDS1	O
)	O
.	O
</s>
<s>
All	O
previous	O
versions	O
of	O
the	O
RSTS	B-Operating_System
file	O
system	O
are	O
given	O
the	O
designation	O
RDS0	O
.	O
</s>
<s>
From	O
1985	O
to	O
1989	O
RSTS	B-Operating_System
became	O
a	O
mature	O
product	O
in	O
the	O
Version	O
9	O
revisions	O
.	O
</s>
<s>
DCL	B-Operating_System
was	O
installed	B-Application
as	O
the	O
primary	O
RTS	B-Device
and	O
the	O
file	O
system	O
was	O
again	O
upgraded	O
(	O
now	O
RDS1.2	O
)	O
to	O
support	O
new	O
user	O
account	O
features	O
.	O
</s>
<s>
Before	O
Version	O
9	O
,	O
there	O
was	O
a	O
non-user	O
system	O
account	O
in	O
the	O
project	O
(	O
group	O
)	O
zero	O
(	O
the	O
designation	O
is	O
 [ 0 , 1 ] 	O
)	O
,	O
and	O
all	O
accounts	O
in	O
project	O
number	O
1	O
were	O
privileged	O
(	O
not	O
unlike	O
the	O
root	O
account	O
on	O
Unix	B-Application
systems	I-Application
)	O
.	O
</s>
<s>
Support	O
for	O
the	O
LAT	B-General_Concept
protocol	I-General_Concept
was	O
included	O
,	O
as	O
well	O
as	O
the	O
ability	O
to	O
run	O
the	O
newest	O
version	O
of	O
DECnet	B-Protocol
IV	O
.	O
</s>
<s>
These	O
network	O
enhancements	O
give	O
any	O
user	O
connected	O
to	O
a	O
terminal	B-General_Concept
through	O
a	O
DECserver	B-Device
the	O
ability	O
to	O
communicate	O
with	O
a	O
RSTS	B-Operating_System
machine	O
,	O
just	O
as	O
easily	O
as	O
with	O
a	O
VAX	B-Device
running	O
VMS	B-Operating_System
.	O
</s>
<s>
The	O
DCL	B-Operating_System
command	O
structure	O
between	O
DEC	O
operating	B-General_Concept
systems	I-General_Concept
also	O
contributed	O
to	O
the	O
familiar	O
look	O
and	O
feel	O
:	O
</s>
<s>
This	O
is	O
not	O
just	O
another	O
pseudo	O
command	O
file	O
processor	B-General_Concept
;	O
it	O
is	O
based	O
on	O
VMS	B-Operating_System
features	O
.	O
</s>
<s>
The	O
DCL	B-Operating_System
command	O
file	O
processor	B-General_Concept
is	O
fully	O
supported	O
and	O
integrated	O
in	O
RSTS	B-Operating_System
through	O
extensive	O
changes	O
to	O
DCL	B-Operating_System
and	O
the	O
monitor	O
.	O
</s>
<s>
DCL	B-Operating_System
executes	O
command	O
files	O
as	O
part	O
of	O
your	O
job	O
;	O
therefore	O
,	O
no	O
pseudo	O
keyboard	O
or	O
forcing	O
of	O
commands	O
to	O
your	O
keyboard	O
is	O
necessary	O
(	O
as	O
with	O
ATPK	O
)	O
.Romanello	O
,	O
G	O
:	O
"	O
A	O
Preview	O
of	O
RSTS/E	B-Operating_System
Version	O
9.0	O
"	O
,	O
page	O
28	O
.	O
</s>
<s>
In	O
1994	O
DEC	O
sold	O
most	O
of	O
its	O
PDP-11	B-Device
software	O
business	O
to	O
Mentec	O
.	O
</s>
<s>
Digital	O
continued	O
to	O
support	O
its	O
own	O
PDP-11	B-Device
customers	O
for	O
a	O
short	O
period	O
after	O
with	O
the	O
assistance	O
of	O
Mentec	O
staff	O
.	O
</s>
<s>
In	O
1997	O
Digital	O
and	O
Mentec	O
granted	O
anyone	O
wishing	O
to	O
use	O
RSTS	B-Operating_System
9.6	O
or	O
earlier	O
for	O
non-commercial	O
,	O
hobby	O
purposes	O
no-cost	O
license	O
.	O
</s>
<s>
The	O
license	O
is	O
only	O
valid	O
on	O
the	O
SIMH	B-Application
PDP-11	B-Device
emulator	O
.	O
</s>
<s>
The	O
license	O
also	O
covers	O
some	O
other	O
Digital	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Copies	O
of	O
the	O
license	O
are	O
included	O
in	O
an	O
authorized	O
software	O
kit	O
available	O
for	O
download	O
on	O
the	O
official	O
website	O
of	O
the	O
SIMH	B-Application
emulator	O
.	O
</s>
<s>
The	O
standard	O
complement	O
of	O
documentation	O
manuals	O
that	O
accompanies	O
a	O
RSTS	B-Operating_System
distribution	O
consists	O
of	O
at	O
least	O
11	O
large	O
three-ring	O
binders	O
(	O
collectively	O
known	O
as	O
"	O
The	O
orange	O
wall	O
"	O
)	O
,	O
one	O
small	O
three-ring	O
binder	O
containing	O
the	O
RSTS/E	B-Operating_System
Quick	O
Reference	O
Guide	O
and	O
a	O
paperback	O
copy	O
of	O
Introduction	O
to	O
BASIC	O
AA-0155B-TK	O
.	O
</s>
<s>
RSTS	B-Operating_System
uses	O
a	O
serial	B-Protocol
communication	I-Protocol
connection	O
to	O
interact	O
with	O
the	O
operator	O
.	O
</s>
<s>
The	O
connection	O
might	O
be	O
a	O
local	O
computer	B-General_Concept
terminal	I-General_Concept
with	O
a	O
20mA	O
current	O
loop	O
interface	O
,	O
an	O
RS-232	O
interface	O
(	O
either	O
local	O
serial	B-Protocol
port	I-Protocol
or	O
remote	O
connection	O
via	O
modem	B-Application
)	O
,	O
or	O
by	O
an	O
Ethernet	O
connection	O
using	O
DECnet	B-Protocol
or	O
LAT	B-General_Concept
.	O
</s>
<s>
As	O
many	O
as	O
128	O
terminals	O
(	O
using	O
multi-terminal	O
service	O
)	O
can	O
connect	O
to	O
a	O
RSTS	B-Operating_System
system	O
,	O
running	O
a	O
maximum	O
of	O
63	O
jobs	O
(	O
depending	O
on	O
the	O
processor	B-General_Concept
being	O
used	O
,	O
the	O
amount	O
of	O
memory	O
and	O
disk	B-Device
space	O
,	O
and	O
the	O
system	O
load	O
)	O
.	O
</s>
<s>
Most	O
RSTS	B-Operating_System
systems	O
had	O
far	O
fewer	O
terminals	O
.	O
</s>
<s>
There	O
is	O
also	O
a	O
batch	O
program	B-Application
called	O
"	O
ATPK	O
"	O
that	O
allows	O
users	O
to	O
run	O
a	O
series	O
of	O
commands	O
on	O
an	O
imaginary	O
terminal	B-General_Concept
(	O
pseudo-terminal	O
)	O
in	O
semi-interactive	O
mode	O
similar	O
to	O
batch	O
commands	O
in	O
MS-DOS	B-Application
.	O
</s>
<s>
Users	O
connect	O
to	O
the	O
system	O
by	O
typing	O
the	O
LOGIN	B-General_Concept
command	O
(	O
or	O
HELLO	O
)	O
at	O
a	O
logged-out	O
terminal	B-General_Concept
and	O
pressing	O
return	O
.	O
</s>
<s>
Typing	O
any	O
command	O
at	O
a	O
logged-out	O
terminal	B-General_Concept
starts	O
the	O
LOGIN	B-General_Concept
program	B-Application
which	O
then	O
interprets	O
the	O
command	O
.	O
</s>
<s>
If	O
it	O
is	O
one	O
of	O
the	O
commands	O
which	O
were	O
allowed	O
to	O
be	O
used	O
by	O
a	O
user	O
that	O
is	O
not	O
yet	O
logged	O
in	O
(	O
"	O
Logged	O
Out	O
"	O
)	O
,	O
then	O
the	O
associated	O
program	B-Application
for	O
that	O
command	O
is	O
CHAINed	O
,	O
otherwise	O
the	O
message	O
"	O
Please	O
say	O
HELLO	O
"	O
is	O
printed	O
on	O
the	O
terminal	B-General_Concept
.	O
</s>
<s>
Prior	O
to	O
Version	O
9	O
,	O
a	O
user	O
can	O
also	O
initiate	O
a	O
1	O
line	O
login	B-General_Concept
,	O
however	O
this	O
leaves	O
the	O
user	O
's	O
password	O
on	O
the	O
screen	O
for	O
anyone	O
else	O
in	O
the	O
room	O
to	O
view	O
(	O
examples	O
follow	O
)	O
:	O
</s>
<s>
The	O
status	O
of	O
a	O
terminal	B-General_Concept
can	O
be	O
determined	O
from	O
the	O
command	O
responses	O
,	O
printed	O
by	O
the	O
command	O
interpreter	O
.	O
</s>
<s>
A	O
logged-in	O
user	O
communicating	O
with	O
the	O
BASIC-PLUS	B-Language
KBM	O
is	O
given	O
the	O
prompt	O
"	O
Ready	O
"	O
and	O
a	O
user	O
who	O
is	O
logged	O
out	O
is	O
given	O
the	O
prompt	O
"	O
Bye	O
"	O
.	O
</s>
<s>
User	O
numbers	O
consist	O
of	O
a	O
project	O
number	O
(	O
equivalent	O
to	O
a	O
group	O
number	O
in	O
Unix	B-Application
)	O
,	O
a	O
comma	O
,	O
and	O
a	O
programmer	O
number	O
.	O
</s>
<s>
When	O
a	O
user	O
is	O
running	O
a	O
system	O
program	B-Application
while	O
logged	O
out	O
(	O
because	O
the	O
system	O
manager	O
has	O
enabled	O
it	O
)	O
their	O
PPN	O
number	O
is	O
[0,0],	O
and	O
appears	O
in	O
the	O
SYSTAT	O
CUSP	O
as	O
**,**	O
.	O
</s>
<s>
If	O
the	O
user	O
specifies	O
a	O
slash	O
(	O
/	O
)	O
instead	O
of	O
a	O
comma	O
between	O
the	O
project	O
number	O
and	O
programmer	O
number	O
,	O
a	O
system	O
wide	O
message	O
stored	O
in	O
[1,2]NOTICE.TXT	O
(	O
equivalent	O
to	O
the	O
Unix	B-Application
motd	O
)	O
will	O
not	O
be	O
displayed	O
at	O
login	B-General_Concept
.	O
</s>
<s>
The	O
project	O
number	O
0	O
is	O
generally	O
reserved	O
for	O
system	B-Application
software	I-Application
,	O
and	O
prior	O
to	O
Version	O
9	O
there	O
is	O
only	O
1	O
project	O
0	O
account	O
(	O
named	O
 [ 0 , 1 ] 	O
)	O
.	O
</s>
<s>
Programmers	O
in	O
the	O
project	O
number	O
1	O
are	O
privileged	O
accounts	O
,	O
equivalent	O
to	O
the	O
single	O
account	O
"	O
root	O
"	O
on	O
Unix	B-Application
systems	I-Application
,	O
except	O
that	O
the	O
account	O
numbers	O
 [ 1 , 0 ] 	O
through	O
 [ 1 , 254 ] 	O
are	O
all	O
privileged	O
accounts	O
.	O
</s>
<s>
As	O
of	O
Version	O
9	O
,	O
any	O
account	O
can	O
be	O
granted	O
specific	O
privileges	O
by	O
the	O
systems	B-Application
manager	I-Application
.	O
</s>
<s>
The	O
account	O
 [ 0 , 1 ] 	O
is	O
used	O
to	O
store	O
the	O
operating	B-General_Concept
system	I-General_Concept
file	O
itself	O
,	O
all	O
run-time	O
library	O
systems	O
,	O
and	O
certain	O
system	O
files	O
relating	O
to	O
booting	B-Operating_System
the	O
system	O
(	O
author	O
's	O
comments	O
appear	O
on	O
the	O
right	O
in	O
bold	O
)	O
:	O
</s>
<s>
The	O
DIR	O
command	O
is	O
an	O
installed	B-Application
CCL	B-Operating_System
equivalent	O
to	O
a	O
RUN	O
command	O
for	O
the	O
DIRECT	O
program	B-Application
.	O
</s>
<s>
 [ 0 , 1 ] 	O
is	O
the	O
account	O
number	O
(	O
and	O
directory	O
name	O
)	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
storage	O
account	O
.	O
</s>
<s>
The	O
numbers	O
shown	O
after	O
each	O
file	O
represent	O
its	O
size	O
in	O
disk	B-Device
blocks	O
,	O
a	O
block	O
being	O
512	O
bytes	B-Application
or	O
1/2	O
kilobyte	O
(	O
K	O
)	O
.	O
</s>
<s>
"	O
C	B-Language
"	O
indicates	O
the	O
file	O
is	O
contiguous	O
(	O
is	O
stored	O
as	O
one	O
file	O
without	O
being	O
separated	O
into	O
pieces	O
,	O
similar	O
to	O
files	O
on	O
a	O
Microsoft	B-Application
Windows	I-Application
system	O
after	O
a	O
drive	O
has	O
been	O
defragmented	B-Application
)	O
,	O
while	O
"	O
P	O
"	O
indicates	O
it	O
is	O
specially	O
protected	O
(	O
cannot	O
be	O
deleted	O
,	O
even	O
by	O
a	O
privileged	O
user	O
,	O
unless	O
the	O
P	O
bit	O
is	O
cleared	O
by	O
separate	O
command	O
)	O
.	O
</s>
<s>
These	O
protection	O
codes	O
are	O
very	O
similar	O
to	O
the	O
r	O
,	O
w	O
and	O
x	O
protections	O
in	O
Unix	B-Application
and	O
similar	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
BSD	B-Operating_System
and	O
Linux	B-Application
.	O
</s>
<s>
The	O
account	O
 [ 1 , 2 ] 	O
is	O
the	O
system	B-Operating_System
startup	I-Operating_System
account	O
(	O
much	O
like	O
a	O
unix	B-Application
system	I-Application
starting	O
up	O
under	O
root	O
)	O
,	O
and	O
contains	O
the	O
system	O
CUSPS	O
that	O
could	O
be	O
referenced	O
by	O
prefixing	O
the	O
CUSP	O
name	O
with	O
a	O
dollar	O
sign	O
( $	O
)	O
.	O
</s>
<s>
Thus	O
the	O
account	O
number	O
 [ 1 , 1 ] 	O
is	O
the	O
closest	O
equivalent	O
to	O
"	O
root	O
"	O
on	O
Unix-based	O
systems	O
.	O
</s>
<s>
One	O
of	O
the	O
features	O
of	O
RSTS	B-Operating_System
is	O
the	O
means	O
for	O
the	O
execution	O
of	O
programs	O
and	O
the	O
environment	O
used	O
to	O
run	O
them	O
.	O
</s>
<s>
The	O
various	O
environments	O
allowed	O
for	O
programming	O
in	O
BASIC-PLUS	B-Language
,	O
the	O
enhanced	O
and	O
hard	O
compiled	B-Language
BASIC-Plus-2	O
,	O
and	O
in	O
more	O
traditional	O
programming	O
languages	O
such	O
as	O
COBOL	B-Application
(	O
eventually	O
upgraded	O
to	O
COBOL-85	O
)	O
and	O
FORTRAN	B-Application
IV	O
(	O
eventually	O
upgraded	O
to	O
FORTRAN-77	O
)	O
.	O
</s>
<s>
Other	O
languages	O
were	O
supported	O
such	O
as	O
DIBOL	B-Language
and	O
MUMPS	B-Language
.	O
</s>
<s>
These	O
environments	O
were	O
separate	O
from	O
each	O
other	O
such	O
that	O
one	O
could	O
start	O
a	O
program	B-Application
from	O
one	O
environment	O
and	O
the	O
system	O
would	O
switch	O
to	O
a	O
different	O
environment	O
while	O
running	O
a	O
different	O
program	B-Application
,	O
and	O
then	O
return	O
the	O
user	O
to	O
the	O
original	O
environment	O
they	O
started	O
with	O
.	O
</s>
<s>
These	O
environments	O
were	O
referred	O
to	O
as	O
a	O
Runtime	B-Device
System	I-Device
(	O
RTS	B-Device
)	O
.	O
</s>
<s>
The	O
term	O
for	O
the	O
command	B-Application
line	I-Application
interface	I-Application
that	O
most	O
of	O
these	O
RTSs	O
had	O
was	O
the	O
KBM	O
.	O
</s>
<s>
Prior	O
to	O
Version	O
9	O
,	O
the	O
systems	B-Application
manager	I-Application
needed	O
to	O
define	O
which	O
RTS	B-Device
the	O
system	O
would	O
start	O
under	O
,	O
and	O
it	O
had	O
to	O
be	O
one	O
that	O
would	O
execute	O
compiled	B-Language
programs	O
.	O
</s>
<s>
A	O
systems	B-Application
manager	I-Application
may	O
also	O
install	O
special	O
CCL	B-Operating_System
commands	O
,	O
which	O
take	O
precedence	O
over	O
all	O
KBM	O
commands	O
(	O
with	O
the	O
exception	O
of	O
DCL	B-Operating_System
)	O
.	O
</s>
<s>
A	O
CCL	B-Operating_System
is	O
analogous	O
to	O
a	O
shortcut	O
to	O
a	O
program	B-Application
on	O
a	O
Windows	O
system	O
or	O
a	O
symbolic	O
link	O
on	O
Unix-based	O
systems	O
.	O
</s>
<s>
CCLs	O
are	O
installed	B-Application
as	O
a	O
memory-resident	O
command	O
either	O
during	O
startup	O
,	O
or	O
dynamically	O
while	O
the	O
system	O
is	O
running	O
by	O
a	O
system	O
's	O
manager	O
(	O
i.e.	O
</s>
<s>
:	O
it	O
is	O
not	O
permanent	O
like	O
a	O
disk	B-Device
file	O
)	O
.	O
</s>
<s>
When	O
logged	O
in	O
,	O
a	O
user	O
can	O
"	O
SWITCH	O
"	O
to	O
any	O
of	O
these	O
environments	O
,	O
type	O
language	O
statements	O
in	O
the	O
BASIC-PLUS	B-Language
programming	O
language	O
,	O
issue	O
RUN	O
commands	O
to	O
specific	O
programs	O
,	O
or	O
issue	O
a	O
special	O
command	O
called	O
a	O
CCL	B-Operating_System
to	O
execute	O
a	O
program	B-Application
with	O
command	O
options	O
.	O
</s>
<s>
Most	O
RSTS	B-Operating_System
systems	O
managers	O
generated	O
the	O
kernel	B-Operating_System
to	O
include	O
the	O
"	O
Control-T	O
"	O
one	O
line	O
status	O
option	O
which	O
could	O
tell	O
the	O
user	O
what	O
program	B-Application
they	O
were	O
running	O
,	O
under	O
what	O
RTS	B-Device
the	O
program	B-Application
was	O
using	O
,	O
how	O
much	O
memory	O
the	O
program	B-Application
was	O
taking	O
,	O
how	O
much	O
it	O
could	O
expand	O
to	O
,	O
and	O
how	O
much	O
memory	O
the	O
RTS	B-Device
was	O
using	O
.	O
</s>
<s>
Programs	O
written	O
in	O
BASIC-PLUS	B-Language
ran	O
under	O
the	O
BASIC	O
RTS	B-Device
,	O
which	O
allowed	O
them	O
up	O
to	O
32K	O
bytes	B-Application
of	O
memory	O
(	O
out	O
of	O
64K	O
total	O
)	O
.	O
</s>
<s>
The	O
language	O
was	O
interpreted	O
,	O
each	O
different	O
keyword	O
being	O
internally	O
converted	O
to	O
a	O
unique	O
byte	B-Application
code	O
and	O
the	O
variables	O
and	O
data	O
being	O
indexed	O
and	O
stored	O
separately	O
within	O
the	O
memory	O
space	O
.	O
</s>
<s>
The	O
internal	O
byte-code	O
format	O
was	O
known	O
as	O
PCODE	O
.	O
</s>
<s>
When	O
the	O
interactive	O
SAVE	O
command	O
was	O
issued	O
,	O
the	O
BASIC	B-Language
Plus	I-Language
RTS	B-Device
simply	O
saved	O
the	O
working	O
memory	O
area	O
to	O
a	O
disk	B-Device
file	O
with	O
a	O
"	O
.BAC	O
"	O
extension	O
.	O
</s>
<s>
Although	O
this	O
format	O
was	O
undocumented	O
,	O
two	O
Electronic	O
Engineering	O
undergraduates	O
from	O
Southampton	O
University	O
in	O
the	O
UK	O
(	O
Nick	O
de	O
Smith	O
and	O
David	O
Garrod	O
)	O
developed	O
a	O
decompiler	O
that	O
could	O
reverse	O
engineer	O
BAC	O
files	O
into	O
their	O
original	O
BASIC-Plus	B-Language
source	O
,	O
complete	O
with	O
original	O
line	O
numbers	O
and	O
variable	O
names	O
(	O
both	O
subsequently	O
worked	O
for	O
DEC	O
)	O
.	O
</s>
<s>
The	O
rest	O
of	O
the	O
memory	O
was	O
used	O
by	O
the	O
BASIC	O
RTS	B-Device
itself	O
.	O
</s>
<s>
If	O
one	O
wrote	O
programs	O
in	O
a	O
language	O
that	O
permitted	O
true	O
binary	O
executables	O
such	O
as	O
BASIC-Plus-2	O
,	O
FORTRAN-IV	O
,	O
or	O
Macro	O
Assembler	B-Language
,	O
then	O
the	O
amount	O
of	O
memory	O
available	O
would	O
be	O
56K	O
(	O
8K	O
allocated	O
to	O
the	O
RTS	B-Device
)	O
.	O
</s>
<s>
The	O
standard	O
BASIC-PLUS	B-Language
prompt	O
is	O
the	O
"	O
Ready	O
"	O
response	O
,	O
pressing	O
Control-T	B-Device
displays	I-Device
status	I-Device
(	O
example	O
)	O
:	O
</s>
<s>
Starting	O
with	O
Version	O
9	O
,	O
DCL	B-Operating_System
became	O
the	O
primary	O
startup	O
RTS	B-Device
even	O
though	O
it	O
does	O
not	O
have	O
the	O
ability	O
to	O
execute	O
binary	O
programs	O
.	O
</s>
<s>
This	O
became	O
possible	O
with	O
the	O
advent	O
of	O
the	O
disappearing	O
RSX	O
RTS	B-Device
(	O
see	O
below	O
)	O
.	O
</s>
<s>
DCL	B-Operating_System
was	O
incorporated	O
into	O
all	O
of	O
the	O
recent	O
versions	O
of	O
DEC	O
's	O
operating	B-General_Concept
systems	I-General_Concept
(	O
RSX-11	B-Application
,	O
RT-11	B-Operating_System
,	O
VMS	B-Operating_System
,	O
and	O
later	O
OpenVMS	B-Operating_System
)	O
for	O
compatibility	O
.	O
</s>
<s>
The	O
standard	O
DCL	B-Operating_System
prompt	O
is	O
the	O
dollar	O
"	O
$	O
"	O
sign	O
(	O
example	O
)	O
:	O
</s>
<s>
Programs	O
that	O
were	O
written	O
for	O
the	O
RSX	O
RTS	B-Device
such	O
as	O
COBOL	B-Application
,	O
Macro	O
Assembler	B-Language
,	O
or	O
later	O
releases	O
of	O
BASIC-Plus-2	O
,	O
could	O
use	O
the	O
maximum	O
amount	O
of	O
memory	O
available	O
for	O
a	O
binary	O
program	B-Application
(	O
56K	O
due	O
to	O
the	O
requirements	O
of	O
an	O
RTS	B-Device
needing	O
the	O
top	O
8K	O
to	O
use	O
for	O
itself	O
)	O
.	O
</s>
<s>
RSTS	B-Operating_System
Version	O
7	O
and	O
later	O
allowed	O
the	O
RSX	O
RTS	B-Device
to	O
be	O
included	O
in	O
the	O
kernel	B-Operating_System
,	O
making	O
it	O
completely	O
"	O
disappear	O
"	O
from	O
the	O
user	O
address	O
space	O
,	O
thus	O
allowing	O
64K	O
bytes	B-Application
of	O
memory	O
for	O
user	O
programs	O
.	O
</s>
<s>
The	O
RT-11	B-Operating_System
RTS	B-Device
emulated	O
the	O
Single	O
Job	O
version	O
of	O
the	O
RT-11	B-Operating_System
distribution	O
.	O
</s>
<s>
Like	O
the	O
RSX	O
emulation	O
,	O
RT-11	B-Operating_System
occupied	O
the	O
top	O
8K	O
of	O
memory	O
,	O
leaving	O
the	O
bottom	O
56K	O
for	O
CUSPS	O
,	O
programs	O
written	O
in	O
FORTRAN-IV	O
or	O
Macro	O
Assembler	B-Language
.	O
</s>
<s>
When	O
RT-11	B-Operating_System
is	O
the	O
default	O
KBM	O
,	O
the	O
standard	O
RT-11	B-Operating_System
prompt	O
(	O
both	O
logged	O
in	O
and	O
logged	O
out	O
)	O
is	O
the	O
"	O
.	O
"	O
</s>
<s>
The	O
TECO	B-Application
editor	I-Application
was	O
itself	O
implemented	O
as	O
an	O
RTS	B-Device
to	O
maximize	O
the	O
amount	O
of	O
memory	O
available	O
for	O
the	O
editing	O
buffer	O
,	O
and	O
also	O
because	O
it	O
was	O
first	O
implemented	O
in	O
RSTS	B-Operating_System
V5B	O
,	O
before	O
the	O
release	O
of	O
the	O
general	O
purpose	O
runtime	B-Device
systems	I-Device
(	O
RSX	O
and	O
RT11	B-Operating_System
)	O
.	O
</s>
<s>
TECO	B-Application
was	O
the	O
only	O
RTS	B-Device
distributed	O
with	O
RSTS	B-Operating_System
that	O
did	O
not	O
contain	O
a	O
built-in	O
KBM	O
.	O
</s>
<s>
The	O
user	O
would	O
start	O
up	O
TECO	B-Application
(	O
like	O
any	O
other	O
program	B-Application
)	O
by	O
running	O
a	O
TECO	B-Application
program	B-Application
(	O
TECO.TEC	O
)	O
.	O
</s>
<s>
TECO	B-Application
and	O
the	O
affine	O
QEDIT	O
were	O
the	O
direct	O
ancestors	O
of	O
the	O
first	O
UNIX-based	O
text	O
editor	O
,	O
ED	O
.	O
</s>
<s>
Most	O
RSTS	B-Operating_System
systems	O
used	O
CCL	B-Operating_System
's	O
to	O
create	O
a	O
file	O
(	O
MAKE	O
filespec	O
)	O
,	O
edit	O
a	O
file	O
(	O
TECO	B-Application
filespec	O
)	O
,	O
or	O
run	O
a	O
TECO	B-Application
program	B-Application
(	O
MUNG	O
filespec	O
,	O
data	O
)	O
.	O
</s>
<s>
The	O
following	O
program	B-Application
is	O
an	O
example	O
of	O
how	O
TECO	B-Application
could	O
be	O
used	O
to	O
calculate	O
pi	O
(	O
currently	O
set	O
to	O
20	O
digits	O
)	O
:	O
</s>
<s>
If	O
a	O
user	O
typed	O
an	O
unrecognized	O
command	O
at	O
system	B-Operating_System
boot	I-Operating_System
to	O
the	O
"	O
Option	O
:	O
"	O
prompt	O
of	O
INIT.SYS	O
,	O
the	O
startup	O
utility	O
,	O
the	O
message	O
"	O
Type	O
'	O
HELP	O
 '	O
for	O
help	O
"	O
was	O
displayed	O
.	O
</s>
<s>
A	O
system	O
manager	O
could	O
compile	B-Language
into	O
the	O
kernel	B-Operating_System
a	O
rotating	O
display	O
pattern	O
that	O
gave	O
the	O
illusion	O
of	O
two	O
snakes	O
chasing	O
each	O
other	O
around	O
the	O
console	O
lights	O
.	O
</s>
<s>
The	O
normal	O
kernel	B-Operating_System
would	O
give	O
the	O
illusion	O
of	O
one	O
snake	O
moving	O
from	O
right	O
to	O
left	O
in	O
the	O
data	O
lights	O
across	O
the	O
bottom	O
.	O
</s>
<s>
If	O
the	O
system	O
manager	O
also	O
compiled	B-Language
the	O
"	O
lights	O
"	O
object	O
module	O
the	O
user	O
would	O
see	O
an	O
additional	O
snake	O
moving	O
from	O
left	O
to	O
right	O
in	O
the	O
address	O
lights	O
across	O
the	O
top	O
.	O
</s>
<s>
The	O
command	O
'	O
make	O
 '	O
allowed	O
a	O
user	O
to	O
make	O
a	O
text	O
file	O
and	O
automatically	O
enter	O
the	O
TECO	B-Application
text	O
editor	O
.	O
</s>
<s>
Kevin	O
Herbert	O
,	O
later	O
working	O
for	O
DEC	O
,	O
added	O
an	O
undocumented	B-General_Concept
feature	I-General_Concept
in	O
the	O
90	O
's	O
to	O
allow	O
a	O
user	O
to	O
enter	O
to	O
see	O
a	O
list	O
of	O
open	O
files	O
the	O
user	O
process	O
had	O
,	O
complete	O
with	O
blocks	O
in	O
use	O
and	O
file	O
sizes	O
.	O
</s>
<s>
Beginning	O
with	O
version	O
9.0	O
,	O
an	O
undocumented	B-General_Concept
feature	I-General_Concept
would	O
allow	O
the	O
system	O
manager	O
to	O
change	O
the	O
display	O
of	O
the	O
system	O
date	O
.	O
</s>
<s>
RSTS	B-Operating_System
became	O
the	O
first	O
operating	B-General_Concept
system	I-General_Concept
that	O
would	O
display	O
the	O
system	O
date	O
as	O
a	O
set	O
of	O
numbers	O
representing	O
a	O
stardate	O
as	O
commonly	O
known	O
from	O
the	O
TV	O
series	O
Star	O
Trek	O
.	O
</s>
<s>
System	O
Industries	O
bought	O
the	O
only	O
source	O
license	O
for	O
RSTS	B-Operating_System
to	O
implement	O
an	O
enhancement	O
called	O
(	O
SImultaneous	O
Machine	O
ACceSs	O
)	O
,	O
which	O
allowed	O
their	O
special	O
disk	B-Device
controller	O
to	O
set	O
a	O
semaphore	B-Operating_System
flag	O
for	O
disk	B-Device
access	O
,	O
allowing	O
multiple	O
WRITES	O
to	O
the	O
same	O
files	O
on	O
a	O
RSTS	B-Operating_System
System	O
where	O
the	O
disk	B-Device
is	O
shared	O
by	O
multiple	O
PDP-11	B-Device
RSTS	B-Operating_System
systems	O
.	O
</s>
<s>
The	O
main	O
innovation	O
was	O
use	O
of	O
a	O
semaphore	B-Operating_System
,	O
a	O
flag	O
to	O
indicate	O
which	O
processor	B-General_Concept
,	O
by	O
cooperative	O
sharing	O
,	O
has	O
exclusive	O
write	O
access	O
.	O
</s>
<s>
This	O
required	O
many	O
changes	O
to	O
the	O
way	O
access	O
to	O
disks	O
was	O
accomplished	O
by	O
the	O
RSTS	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
The	O
FIPS	O
(	O
File	O
Information	O
Processing	O
System	O
)	O
system	O
,	O
that	O
handled	O
i/o	O
access	O
,	O
was	O
single-threaded	O
in	O
RSTS	B-Operating_System
.	O
</s>
<s>
To	O
allow	O
a	O
disk	B-Device
access	O
to	O
stall	O
while	O
another	O
machine	O
had	O
active	O
access	O
to	O
a	O
block	O
,	O
required	O
that	O
the	O
FIPS	O
could	O
timeout	O
a	O
request	O
,	O
go	O
to	O
the	O
next	O
request	O
and	O
'	O
come	O
back	O
 '	O
to	O
the	O
stalled	O
one	O
in	O
a	O
round	O
robin	O
fashion	O
.	O
</s>
<s>
SIMACS	O
was	O
not	O
limited	O
to	O
the	O
PDP-11	B-Device
product	O
line	O
;	O
VAXen	B-Device
could	O
also	O
use	O
it	O
.	O
</s>
<s>
ROSS/V	O
allowed	O
all	O
user	B-Operating_System
mode	I-Operating_System
processes	O
of	O
RSTS	B-Operating_System
(	O
CUSPS	O
,	O
RTSs	O
and	O
user	O
programs	O
)	O
the	O
ability	O
to	O
run	O
unmodified	O
under	O
VMS	B-Operating_System
on	O
the	O
VAX-11	O
machines	O
.	O
</s>
<s>
The	O
code	O
for	O
this	O
emulation	O
handled	O
all	O
of	O
the	O
kernel	B-Operating_System
processes	O
that	O
would	O
normally	O
be	O
handled	O
by	O
a	O
RSTS	B-Operating_System
kernel	B-Operating_System
running	O
on	O
a	O
PDP-11	B-Device
.	O
</s>
<s>
The	O
original	O
BASIC-PLUS	B-Language
language	O
that	O
has	O
carried	O
through	O
all	O
versions	O
of	O
RSTS	B-Operating_System
was	O
subcontracted	O
by	O
Evans	O
Griffiths	O
&	O
Hart	O
,	O
Inc	O
.	O
for	O
a	O
fixed	O
price	O
of	O
$	O
10,500	O
.	O
</s>
<s>
RSTS	B-Operating_System
and	O
its	O
applications	O
can	O
run	O
under	O
a	O
number	O
of	O
PDP-11	B-Device
emulators	O
such	O
as	O
SIMH	B-Application
and	O
Ersatz-11	O
.	O
</s>
<s>
For	O
more	O
information	O
,	O
see	O
PDP-11	B-Device
.	O
</s>
<s>
RSTS	B-Operating_System
was	O
originally	O
called	O
BTSS	O
(	O
Basic	O
Time	B-General_Concept
Sharing	I-General_Concept
System	O
)	O
.	O
</s>
<s>
A	O
simple	O
typing	O
mistake	O
changed	O
the	O
name	O
from	O
RTSS	O
to	O
RSTS	B-Operating_System
.	O
</s>
<s>
Version	O
Release	O
date	O
Notes	O
1	O
Never	O
released	O
2A-19	O
1971	O
Installed	B-Application
at	O
Carleton	O
College	O
and	O
Seattle	O
Pacific	O
College	O
.	O
</s>
<s>
2B	O
June	O
1971	O
Installed	B-Application
at	O
the	O
Delaware	O
School	O
Auxiliary	O
Association	O
.	O
</s>
<s>
The	O
addition	O
of	O
new	O
memory	B-General_Concept
management	I-General_Concept
support	O
and	O
the	O
ability	O
to	O
install	O
more	O
memory	O
in	O
the	O
PDP-11/40	B-Device
and	O
PDP-11/45	B-Device
led	O
to	O
another	O
name	O
change	O
:	O
RSTS-11	B-Operating_System
now	O
became	O
RSTS/E	B-Operating_System
.	O
</s>
<s>
Version	O
Release	O
date	O
Notes	O
5A-21	O
July	O
1973	O
Memory	B-General_Concept
management	I-General_Concept
extensions	O
from	O
64KB	O
to	O
256KB	O
.	O
</s>
<s>
5B-24	O
November	O
1974	O
Multiple	O
SWAP	O
files	O
,	O
RTS	B-Device
and	O
CCL	B-Operating_System
introduced	O
.	O
</s>
<s>
6B-02	O
February	O
1977	O
New	O
hardware	O
,	O
SYSGEN	B-Application
under	O
RT-11	B-Operating_System
,	O
CCL	B-Operating_System
at	O
runtime	O
.	O
</s>
<s>
6C-03	O
February	O
1978	O
DECnet	B-Protocol
Phase	O
II	O
,	O
DTR	O
,	O
DIBOL	B-Language
supported	O
.	O
</s>
<s>
7.1	O
February	O
1981	O
Kernel	B-Operating_System
mode	O
Instruction	O
&	O
Data	O
space	O
support	O
,	O
DECnet	B-Protocol
Phase	O
III	O
.	O
</s>
<s>
9.0-14	O
May	O
1985	O
New	O
hardware	O
,	O
DCL	B-Operating_System
default	O
,	O
PBS	O
,	O
multiple	O
privs	O
,	O
hashed	O
passwords	O
,	O
new	O
Backup	O
utility	O
,	O
and	O
Stardate	O
.	O
</s>
<s>
9.3-20	O
January	O
1987	O
Enhanced	O
hardware	O
support	O
,	O
DECnet	B-Protocol
Phase	O
IV	O
.	O
</s>
<s>
9.4	O
July	O
1987	O
New	O
hardware	O
,	O
Scheduler	O
and	O
Terminal	B-General_Concept
Service	O
improvements	O
.	O
</s>
<s>
9.6	O
September	O
1988	O
LAT	B-General_Concept
support	O
,	O
HELP	O
SPIKE	O
.	O
</s>
<s>
10.0	O
May	O
1990	O
Command	B-Application
line	I-Application
history	O
in	O
TTDRV	O
.	O
</s>
<s>
Computer	O
bureaus	O
sometimes	O
deployed	O
User-11	O
for	O
RSTS/E	B-Operating_System
-based	O
data	B-General_Concept
management	I-General_Concept
.	O
</s>
