<s>
The	O
Autonetics	B-Device
RECOMP	I-Device
II	I-Device
was	O
a	O
computer	O
first	O
introduced	O
in	O
1958	O
.	O
</s>
<s>
Memory	O
and	O
registers	O
were	O
on	O
a	O
fixed	O
head	O
disk	O
that	O
operated	O
like	O
a	O
drum	B-General_Concept
memory	I-General_Concept
—	O
4080	O
words	O
on	O
standard	O
tracks	O
,	O
16	O
words	O
on	O
fast	O
loop	O
tracks	O
,	O
registers	O
A	O
,	O
B	O
,	O
R	O
,	O
X	O
each	O
on	O
their	O
own	O
high-speed	O
loop	O
track	O
,	O
and	O
one	O
prerecorded	O
read	B-Device
only	I-Device
clock	O
track	O
.	O
</s>
<s>
Since	O
indexing	O
was	O
commonly	O
done	O
by	O
modifying	O
the	O
address	O
part	O
of	O
an	O
instruction	O
(	O
say	O
,	O
by	O
adding	O
one	O
to	O
access	O
the	O
next	O
data	O
item	O
in	O
a	O
list	O
)	O
,	O
such	O
instructions	O
always	O
had	O
to	O
be	O
in	O
the	O
second	O
half-word	O
,	O
and	O
the	O
first	O
half-word	O
was	O
padded	O
with	O
a	O
NOP	B-Language
instruction	O
.	O
</s>
<s>
Programmers	O
also	O
used	O
these	O
NOP	B-Language
instructions	O
to	O
provide	O
space	O
for	O
future	O
inserted	O
instructions	O
,	O
since	O
the	O
assembler	O
did	O
not	O
allow	O
for	O
use	O
of	O
symbolic	O
addresses	O
,	O
and	O
the	O
insertion	O
of	O
a	O
single	O
instruction	O
could	O
otherwise	O
require	O
rewriting	O
a	O
lot	O
of	O
code	O
.	O
</s>
<s>
The	O
machine	O
had	O
a	O
bit-serial	B-General_Concept
architecture	I-General_Concept
.	O
</s>
