<s>
The	O
SDS	B-Device
940	I-Device
was	O
Scientific	O
Data	O
Systems	O
 '	O
(	O
SDS	O
)	O
first	O
machine	O
designed	O
to	O
directly	O
support	O
time-sharing	B-General_Concept
.	O
</s>
<s>
The	O
940	O
was	O
based	O
on	O
the	O
SDS	B-Device
930	I-Device
's	O
24-bit	O
CPU	B-General_Concept
,	O
with	O
additional	O
circuitry	O
to	O
provide	O
protected	B-General_Concept
memory	I-General_Concept
and	O
virtual	B-Architecture
memory	I-Architecture
.	O
</s>
<s>
This	O
machine	O
was	O
later	O
used	O
to	O
run	O
Community	O
Memory	O
,	O
the	O
first	O
bulletin	B-Application
board	I-Application
system	I-Application
.	O
</s>
<s>
After	O
SDS	O
was	O
acquired	O
by	O
Xerox	O
in	O
1969	O
and	O
became	O
Xerox	O
Data	O
Systems	O
,	O
the	O
SDS	B-Device
940	I-Device
was	O
renamed	O
as	O
the	O
XDS	B-Device
940	I-Device
.	O
</s>
<s>
Genie	O
added	O
memory	B-General_Concept
management	I-General_Concept
and	O
controller	O
logic	O
to	O
an	O
existing	O
SDS	B-Device
930	I-Device
computer	O
to	O
give	O
it	O
page-mapped	B-General_Concept
virtual	B-Architecture
memory	I-Architecture
,	O
which	O
would	O
be	O
heavily	O
copied	O
by	O
other	O
designs	O
.	O
</s>
<s>
Like	O
most	O
systems	O
of	O
the	O
era	O
,	O
the	O
machine	O
was	O
built	O
with	O
a	O
bank	O
of	O
core	B-General_Concept
memory	I-General_Concept
as	O
the	O
primary	O
storage	O
,	O
allowing	O
between	O
16	O
and	O
64	O
kilowords	O
.	O
</s>
<s>
Words	O
were	O
24	O
bits	O
plus	O
a	O
parity	B-Error_Name
bit	I-Error_Name
.	O
</s>
<s>
This	O
was	O
backed	O
up	O
by	O
a	O
variety	O
of	O
secondary	O
storage	O
devices	O
,	O
including	O
a	O
1376	O
kword	O
drum	O
in	O
Genie	O
,	O
or	O
hard	B-Device
disks	I-Device
in	O
the	O
SDS	O
models	O
in	O
the	O
form	O
of	O
a	O
drum-like	O
2097	O
kword	O
"	O
fixed-head	O
"	O
disk	B-Device
or	O
a	O
traditional	O
"	O
floating-head	O
"	O
model	O
.	O
</s>
<s>
They	O
bootstrapped	B-Operating_System
from	O
paper	O
tape	O
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
developed	O
at	O
Project	O
Genie	O
was	O
the	O
Berkeley	B-General_Concept
Timesharing	I-General_Concept
System	I-General_Concept
.	O
</s>
<s>
By	O
August	O
1968	O
a	O
version	O
2.0	O
was	O
announced	O
that	O
was	O
just	O
called	O
the	O
"	O
SDS	B-Device
940	I-Device
Time-Sharing	B-General_Concept
System	I-General_Concept
"	O
.	O
</s>
<s>
As	O
of	O
1969	O
,	O
the	O
XDS	B-Device
940	I-Device
software	O
system	O
consisted	O
of	O
the	O
following	O
:	O
</s>
<s>
Additional	O
software	O
was	O
available	O
from	O
the	O
XDS	O
Users	O
 '	O
Group	O
Library	O
,	O
such	O
as	O
a	O
string-processing	O
system	O
,	O
"	O
SYSPOPs	O
"	O
(	O
system	O
programmed	O
operators	O
,	O
which	O
allow	O
access	O
to	O
system	O
services	O
)	O
,	O
CAL	B-Language
(	O
Conversational	O
Algebraic	O
Language	O
,	O
a	O
dialect	O
of	O
JOSS	B-Language
)	O
,	O
QED	B-Application
(	O
a	O
text	O
editor	O
)	O
,	O
TAP	O
(	O
Time-sharing	B-General_Concept
Assembly	O
Program	O
,	O
an	O
assembler	O
)	O
,	O
and	O
DDT	B-Operating_System
,	O
a	O
debugging	B-Application
tool	I-Application
.	O
</s>
<s>
A	O
cathode-ray	B-Device
tube	I-Device
display	O
with	O
26	O
lines	O
that	O
operated	O
DDT	B-Operating_System
loader-debugger	O
that	O
were	O
originally	O
designed	O
to	O
operate	O
from	O
a	O
teletype	O
terminal	O
were	O
also	O
available	O
.	O
</s>
<s>
The	O
major	O
customer	O
was	O
Tymshare	O
,	O
who	O
used	O
the	O
system	O
to	O
become	O
the	O
USA	O
's	O
best	O
known	O
commercial	O
timesharing	B-General_Concept
service	O
in	O
the	O
late	O
1960s	O
.	O
</s>
<s>
Tymshare	O
,	O
Comshare	O
and	O
UC	O
Berkeley	O
collaborated	O
in	O
much	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
development	O
for	O
the	O
SDS	B-Device
940	I-Device
.	O
</s>
<s>
Douglas	O
Engelbart	O
's	O
Augmentation	O
Research	O
Center	O
(	O
ARC	O
)	O
used	O
an	O
SDS	B-Device
940	I-Device
for	O
their	O
oN-Line	O
System	O
,	O
more	O
commonly	O
known	O
as	O
NLS	O
.	O
</s>
<s>
The	O
first	O
host	O
connected	O
to	O
the	O
ARPANET	O
was	O
an	O
SDS	B-Device
940	I-Device
at	O
SRI	O
in	O
October	O
,	O
1969	O
.	O
</s>
<s>
A	O
San	O
Francisco	O
counterculture	O
community	O
action	O
group	O
called	O
Resource	O
One	O
and	O
located	O
in	O
Project	O
One	O
used	O
a	O
donated	O
surplus	O
XDS	B-Device
940	I-Device
as	O
described	O
in	O
Rolling	O
Stone	O
magazine	O
in	O
1972	O
.	O
</s>
<s>
The	O
Community	O
Memory	O
project	O
served	O
as	O
an	O
early	O
electronic	B-Application
bulletin	I-Application
board	I-Application
system	O
.	O
</s>
