<s>
The	O
Xerox	B-Device
500	I-Device
series	I-Device
is	O
a	O
discontinued	O
line	O
of	O
computers	O
from	O
Xerox	O
Data	O
Systems	O
(	O
XDS	O
)	O
introduced	O
in	O
the	O
early	O
1970s	O
as	O
backward-compatible	B-General_Concept
upgrades	O
for	O
the	O
Sigma	B-Device
series	I-Device
machines	I-Device
.	O
</s>
<s>
Although	O
orders	O
for	O
the	O
Xerox	B-Device
530	I-Device
were	O
deemed	O
"	O
encouraging	O
"	O
as	O
of	O
January	O
1974	O
,	O
</s>
<s>
Binary	O
integer	O
arithmetic	O
is	O
standard	O
on	O
all	O
models	O
;	O
floating-point	B-Algorithm
is	O
optional	O
on	O
the	O
530	O
,	O
and	O
standard	O
on	O
the	O
550	O
and	O
560	O
.	O
</s>
<s>
The	O
560	O
also	O
supports	O
decimal	B-Algorithm
arithmetic	I-Algorithm
.	O
</s>
<s>
Systems	O
are	O
clusterable	O
,	O
with	O
multiple	O
"	O
basic	O
processors	O
"	O
(	O
BPs	O
)	O
,	O
I/O	O
processors	O
(	O
IOPs	O
)	O
,	O
and	O
"	O
system	O
control	O
processors	O
"	O
(	O
CPs	O
)	O
sharing	O
busses	B-General_Concept
and	O
memory	O
.	O
</s>
<s>
The	O
Xerox	B-Device
530	I-Device
system	O
is	O
a	O
16-bit	B-Device
computer	I-Device
aimed	O
at	O
upgrading	O
the	O
16-bit	B-Device
Sigma	B-Device
2	I-Device
and	O
3	O
systems	O
.	O
</s>
<s>
The	O
530	O
supports	O
memory	O
sizes	O
of	O
8K	O
to	O
64K	O
16-bit	B-Device
words	O
(	O
16KB	O
to	O
128KB	O
)	O
with	O
a	O
cycle	O
time	O
of	O
800ns	O
.	O
</s>
<s>
The	O
memory	O
protection	O
feature	O
protects	O
the	O
foreground	O
(	O
real-time	B-General_Concept
)	O
program	O
from	O
the	O
background	O
tasks	O
.	O
</s>
<s>
When	O
IBM	O
discontinued	O
the	O
16-bit	B-Device
IBM	B-Device
1130	I-Device
,	O
Xerox	O
began	O
marketing	O
the	O
530	O
as	O
a	O
possible	O
successor	O
,	O
</s>
<s>
Both	O
the	O
1130	O
and	O
Xerox	B-Device
530	I-Device
had	O
Indirect	O
addressing	O
and	O
8-bit	O
relative	O
addressing	O
.	O
</s>
<s>
On	O
the	O
IBM	O
1130/1800	O
magnetic	B-Architecture
tape	I-Architecture
drives	I-Architecture
were	O
only	O
available	O
as	O
a	O
special	O
feature	O
—	O
RPQ	O
(	O
Request	O
Price	O
Quotation	O
)	O
.	O
</s>
<s>
The	O
Xerox	B-Device
530	I-Device
offered	O
a	O
choice	O
of	O
7-track	O
drives	O
operating	O
at	O
37.5	O
inches	O
per	O
second	O
(	O
ips	O
)	O
or	O
nine-track	O
,	O
75	O
ips	O
drives	O
.	O
</s>
<s>
The	O
Xerox	B-Device
550	I-Device
and	O
Xerox	B-Device
560	I-Device
systems	O
are	O
32-bit	O
computers	O
introduced	O
in	O
1974	O
.	O
</s>
<s>
The	O
550	O
was	O
aimed	O
at	O
real-time	B-General_Concept
applications	I-General_Concept
and	O
intended	O
as	O
an	O
upgrade	O
for	O
the	O
Sigma	B-Device
5	I-Device
.	O
</s>
<s>
The	O
systems	O
are	O
microprogrammed	B-Device
and	O
constructed	O
using	O
large-scale	O
and	O
medium-scale	O
integration	O
(	O
LSI	O
and	O
MSI	O
)	O
and	O
magnetic-core	O
memory	O
.	O
</s>
<s>
Virtual	B-Architecture
memory	I-Architecture
and	O
memory	O
protection	O
are	O
standard	O
features	O
.	O
</s>
<s>
The	O
530	O
can	O
run	O
either	O
the	O
Basic	O
Control	O
Monitor	O
(	O
BCM	O
)	O
or	O
the	O
Real-time	B-General_Concept
Batch	O
Monitor	O
(	O
RBM	O
)	O
operating	O
systems	O
.	O
</s>
<s>
RBM	O
supports	O
a	O
combination	O
of	O
real-time	B-General_Concept
and	O
general-purpose	O
batch	O
jobs	O
running	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
The	O
550	O
runs	O
the	O
Control	O
Program	O
for	O
Real-Time	B-General_Concept
(	O
CP-R	O
)	O
operating	O
system	O
,	O
or	O
the	O
CP-V	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
.	O
</s>
<s>
Much	O
as	O
IBM	O
's	O
Job	B-Application
Control	I-Application
Language	I-Application
statements	O
begin	O
with	O
//	O
(	O
Slash-Slash	O
)	O
,	O
Xerox	O
uses	O
an	O
exclamation	O
point	O
(	O
!	O
</s>
