<s>
The	O
CDC	B-Device
160	I-Device
series	I-Device
was	O
a	O
series	O
of	O
minicomputers	B-Architecture
built	O
by	O
Control	O
Data	O
Corporation	O
.	O
</s>
<s>
The	O
CDC	B-Device
160	I-Device
and	O
CDC	B-Device
160-A	I-Device
were	O
12-bit	O
minicomputers	B-Architecture
built	O
from	O
1960	O
to	O
1965	O
;	O
the	O
CDC	O
160G	O
was	O
a	O
13-bit	O
minicomputer	B-Architecture
,	O
with	O
an	O
extended	O
version	O
of	O
the	O
CDC	B-Device
160-A	I-Device
instruction	O
set	O
,	O
and	O
a	O
compatibility	O
mode	O
in	O
which	O
it	O
did	O
not	O
use	O
the	O
13th	O
bit	O
.	O
</s>
<s>
A	O
publishing	O
company	O
that	O
purchased	O
a	O
CDC	B-Device
160-A	I-Device
described	O
it	O
as	O
"	O
a	O
single	O
user	O
machine	O
with	O
no	O
batch	O
processing	O
capability	O
.	O
</s>
<s>
The	O
CDC	B-Device
160-A	I-Device
was	O
a	O
simple	O
piece	O
of	O
hardware	O
,	O
and	O
yet	O
provided	O
a	O
variety	O
of	O
features	O
which	O
were	O
scaled-down	O
capabilities	O
found	O
only	O
on	O
larger	O
systems	O
.	O
</s>
<s>
It	O
was	O
therefore	O
an	O
ideal	O
platform	O
for	O
introducing	O
neophyte	O
programmers	O
to	O
the	O
sophisticated	O
concepts	O
of	O
low-level	O
input/output	B-General_Concept
(	O
I/O	B-General_Concept
)	O
and	O
interrupt	B-Application
systems	O
.	O
</s>
<s>
All	O
160	O
systems	O
had	O
a	O
paper-tape	O
reader	O
,	O
and	O
a	O
punch	O
,	O
and	O
most	O
had	O
an	O
IBM	O
Electric	O
typewriter	O
modified	O
to	O
act	O
as	O
a	O
computer	B-General_Concept
terminal	I-General_Concept
.	O
</s>
<s>
Return-jump	O
allowed	O
simple	O
subroutine	O
calls	O
and	O
bank	B-General_Concept
switching	I-General_Concept
allowed	O
other	O
4K	O
banks	O
of	O
memory	O
to	O
be	O
addressed	O
,	O
albeit	O
clumsily	O
,	O
up	O
to	O
a	O
total	O
of	O
32,768	O
words	O
.	O
</s>
<s>
Low-level	O
I/O	B-General_Concept
allowed	O
control	O
of	O
devices	O
,	O
interfacing	O
for	O
determining	O
device	O
status	O
,	O
and	O
for	O
reading	O
and	O
writing	O
data	O
as	O
either	O
single	O
bytes	O
,	O
or	O
as	O
blocks	O
.	O
</s>
<s>
I/O	B-General_Concept
could	O
be	O
completed	O
to	O
a	O
register	O
,	O
or	O
to	O
memory	O
,	O
or	O
via	O
a	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
(	O
DMA	O
)	O
channel	O
.	O
</s>
<s>
The	O
distinction	O
between	O
these	O
I/O	B-General_Concept
types	O
was	O
that	O
regular	O
I/O	B-General_Concept
would	O
'	O
hang	O
 '	O
the	O
CPU	O
until	O
the	O
I/O	B-General_Concept
operation	I-General_Concept
completed	O
,	O
but	O
DMA	O
I/O	B-General_Concept
allowed	O
the	O
CPU	O
to	O
proceed	O
with	O
instruction	O
execution	O
concurrently	O
with	O
the	O
data	O
transfer	O
.	O
</s>
<s>
The	O
interrupt	B-Application
system	O
was	O
purely	O
based	O
on	O
IO	O
,	O
meaning	O
that	O
all	O
interrupts	B-Application
were	O
generated	O
externally	O
.	O
</s>
<s>
Interrupts	B-Application
were	O
introduced	O
to	O
neophytes	O
as	O
being	O
the	O
alert	O
mechanism	O
by	O
which	O
a	O
program	O
could	O
be	O
informed	O
that	O
a	O
previously	O
initiated	O
DMA	O
I/O	B-General_Concept
operation	I-General_Concept
was	O
completed	O
.	O
</s>
<s>
The	O
160	O
architecture	O
was	O
modified	O
to	O
become	O
the	O
basis	O
of	O
the	O
peripheral	O
processors	O
(	O
PPs	O
)	O
in	O
the	O
CDC	B-Device
6000	I-Device
series	I-Device
mainframe	O
computers	O
and	O
its	O
successors	O
.	O
</s>
<s>
In	O
the	O
early	O
days	O
of	O
the	O
6000s	O
,	O
almost	O
the	O
entire	O
operating	B-General_Concept
system	I-General_Concept
ran	O
in	O
the	O
PPs	O
.	O
</s>
<s>
This	O
left	O
the	O
central	O
processor	O
unencumbered	O
by	O
operating	B-General_Concept
system	I-General_Concept
demands	O
and	O
available	O
for	O
user	O
programs	O
.	O
</s>
