<s>
It	O
was	O
derived	O
from	O
the	O
RCA	B-Device
Spectra	I-Device
70	I-Device
range	O
,	O
itself	O
a	O
variant	O
of	O
the	O
IBM	B-Application
System	I-Application
360	I-Application
architecture	O
.	O
</s>
<s>
The	O
System	O
4-50	O
and	O
4-70	O
were	O
intended	O
for	O
real-time	O
applications	O
,	O
for	O
they	O
had	O
four	O
processor	O
states	O
,	O
each	O
with	O
its	O
own	O
set	O
of	O
general-purpose	B-General_Concept
registers	I-General_Concept
(	O
GPR	B-General_Concept
)	O
.	O
</s>
<s>
Although	O
some	O
states	O
did	O
not	O
have	O
all	O
16	O
GPRs	B-General_Concept
,	O
nevertheless	O
,	O
the	O
design	O
avoided	O
having	O
to	O
save	O
registers	O
when	O
switching	O
between	O
processor	O
states	O
.	O
</s>
<s>
The	O
instructions	O
available	O
in	O
this	O
state	O
were	O
the	O
non-privileged	O
instructions	O
of	O
the	O
IBM	B-Application
System	I-Application
360	I-Application
.	O
</s>
<s>
In	O
processor	O
states	O
P1	O
and	O
P2	O
,	O
16	O
GPRs	B-General_Concept
were	O
available	O
;	O
in	O
State	O
P3	O
,	O
6	O
GPRs	B-General_Concept
were	O
available	O
,	O
while	O
in	O
State	O
P4	O
,	O
5	O
GPRs	B-General_Concept
were	O
available	O
.	O
</s>
<s>
The	O
non-privileged	O
instruction	O
set	O
of	O
the	O
System	O
4-50	O
and	O
4-70	O
included	O
the	O
integer	O
,	O
floating-point	O
,	O
character	O
,	O
and	O
decimal	O
instructions	O
—	O
in	O
short	O
,	O
the	O
full	O
non-privileged	O
instruction	O
set	O
of	O
the	O
IBM	B-Application
System	I-Application
360	I-Application
,	O
except	O
for	O
Test	O
and	O
Set	O
(	O
TS	O
)	O
.	O
</s>
<s>
One	O
System	O
4-75	O
was	O
used	O
at	O
the	O
ERCC	O
to	O
develop	O
the	O
EMAS	B-Application
interactive	O
operating	O
system	O
.	O
</s>
