<s>
The	O
NCR	B-Device
315	I-Device
Data	O
Processing	O
System	O
,	O
released	O
in	O
January	O
1962	O
by	O
NCR	O
,	O
is	O
a	O
second-generation	O
computer	O
.	O
</s>
<s>
It	O
uses	O
12-bit	B-Device
slab	O
memory	O
structure	O
using	O
magnetic-core	O
memory	O
.	O
</s>
<s>
Basic	O
memory	O
is	O
5000	O
"	O
slabs	O
"	O
(	O
10,000	O
characters	O
or	O
15,000	O
decimal	B-Application
digits	O
)	O
of	O
handmade	O
core	O
memory	O
,	O
which	O
is	O
expandable	O
to	O
a	O
maximum	O
of	O
40,000	O
slabs	O
(	O
80,000	O
characters	O
or	O
120,000	O
decimal	B-Application
digits	O
)	O
in	O
four	O
refrigerator-size	O
cabinets	O
.	O
</s>
<s>
The	O
main	O
processor	O
includes	O
three	O
cabinets	O
and	O
a	O
console	O
section	O
that	O
houses	O
the	O
power	O
supply	O
,	O
keyboard	O
,	O
output	O
writer	O
(	O
an	O
IBM	O
electric	O
typewriter	O
)	O
,	O
and	O
a	O
panel	B-Device
with	O
lights	O
that	O
indicate	O
the	O
current	O
status	O
of	O
the	O
program	O
counter	O
,	O
registers	O
,	O
arithmetic	O
accumulator	B-General_Concept
,	O
and	O
system	O
errors	O
.	O
</s>
<s>
Some	O
devices	O
like	O
magnetic	O
tape	O
and	O
the	O
CRAM	B-Device
are	O
daisy-chained	O
to	O
allow	O
multiple	O
drives	O
to	O
be	O
connected	O
.	O
</s>
<s>
Later	O
models	O
in	O
this	O
series	O
include	O
the	O
315-100	B-Device
and	O
the	O
315-RMC	O
(	O
Rod	O
Memory	O
Computer	O
)	O
.	O
</s>
<s>
The	O
addressable	O
unit	O
of	O
memory	O
on	O
the	O
NCR	B-Device
315	I-Device
series	O
is	O
a	O
"	O
slab	O
"	O
,	O
short	O
for	O
"	O
syllable	B-General_Concept
"	O
,	O
consisting	O
of	O
12	O
data	O
bits	O
and	O
a	O
parity	B-Error_Name
bit	I-Error_Name
.	O
</s>
<s>
Its	O
size	O
falls	O
between	O
a	O
byte	B-Application
and	O
a	O
typical	O
word	O
(	O
hence	O
the	O
name	O
,	O
'	O
syllable	B-General_Concept
 '	O
)	O
.	O
</s>
<s>
A	O
slab	O
may	O
contain	O
a	O
decimal	B-Application
value	O
from	O
-99	O
to	O
+999	O
.	O
</s>
<s>
A	O
numeric	B-Algorithm
value	O
contains	O
up	O
to	O
eight	O
slabs	O
.	O
</s>
<s>
These	O
commands	O
use	O
the	O
accumulator	B-General_Concept
,	O
which	O
has	O
a	O
maximum	O
length	O
of	O
eight	O
slabs	O
.	O
</s>
<s>
To	O
accelerate	O
the	O
processing	O
the	O
accumulator	B-General_Concept
works	O
with	O
an	O
effective	O
length	O
.	O
</s>
<s>
The	O
NCR	B-Device
315-100	I-Device
is	O
the	O
second	O
version	O
of	O
the	O
original	O
315	O
.	O
</s>
<s>
The	O
315-100	B-Device
series	O
console	O
I/O	O
incorporates	O
a	O
Teletype	O
printer	O
and	O
keyboard	O
in	O
place	O
of	O
the	O
original	O
315	O
's	O
IBM	O
typewriter	O
.	O
</s>
<s>
The	O
primary	O
difference	O
between	O
the	O
older	O
NCR	B-Device
315	I-Device
and	O
the	O
315-100	B-Device
was	O
the	O
inclusion	O
of	O
the	O
Automatic	O
Recovery	O
Option	O
(	O
ARO	O
)	O
.	O
</s>
<s>
The	O
normal	O
recovery	O
process	O
was	O
to	O
copy	O
all	O
register	O
and	O
counter	O
setting	O
from	O
the	O
console	O
light	O
panel	B-Device
,	O
and	O
to	O
restart	O
the	O
program	O
that	O
was	O
running	O
at	O
the	O
time	O
of	O
the	O
error	O
,	O
usually	O
from	O
the	O
very	O
beginning	O
of	O
the	O
program	O
.	O
</s>
<s>
The	O
NCR	B-Device
315-RMC	I-Device
,	O
released	O
in	O
July	O
1965	O
,	O
was	O
the	O
first	O
commercially	O
available	O
computer	O
to	O
employ	O
thin-film	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
It	O
also	O
included	O
floating-point	B-Algorithm
logic	O
to	O
allow	O
scientific	O
calculations	O
,	O
while	O
retaining	O
the	O
same	O
instruction	O
set	O
as	O
previous	O
NCR	B-Device
315	I-Device
and	O
NCR	B-Device
315-100	I-Device
.	O
</s>
<s>
The	O
follow-on	O
to	O
the	O
315-RMC	O
was	O
the	O
NCR	B-Device
Century	I-Device
series	O
.	O
</s>
