<s>
18	B-General_Concept
bits	I-General_Concept
was	O
a	O
common	O
word	O
size	O
for	O
smaller	O
computers	O
in	O
the	O
1960s	O
,	O
when	O
large	O
computers	O
often	O
used	O
36	O
bit	O
words	O
and	O
6-bit	O
character	O
sets	O
,	O
sometimes	O
implemented	O
as	O
extensions	O
of	O
BCD	O
,	O
were	O
the	O
norm	O
.	O
</s>
<s>
There	O
were	O
also	O
18-bit	B-General_Concept
teletypes	O
experimented	O
with	O
in	O
the	O
1940s	O
.	O
</s>
<s>
Possibly	O
the	O
most	O
well-known	O
18-bit	B-General_Concept
computer	O
architectures	O
are	O
the	O
PDP-1	B-Device
,	O
PDP-4	B-Device
,	O
PDP-7	B-Device
,	O
PDP-9	B-Device
and	O
PDP-15	B-Device
minicomputers	B-Architecture
produced	O
by	O
Digital	O
Equipment	O
Corporation	O
from	O
1960	O
to	O
1975	O
.	O
</s>
<s>
Digital	O
's	O
PDP-10	B-Device
used	O
36-bit	O
words	O
but	O
had	O
18-bit	B-General_Concept
addresses	O
.	O
</s>
<s>
The	O
UNIVAC	O
produced	O
several	O
18-bit	B-General_Concept
computers	O
,	O
including	O
the	O
UNIVAC	B-Device
418	I-Device
and	O
several	O
military	O
systems	O
.	O
</s>
<s>
The	O
IBM	B-Device
7700	I-Device
Data	I-Device
Acquisition	I-Device
System	I-Device
was	O
announced	O
by	O
IBM	O
on	O
December	O
2	O
,	O
1963	O
.	O
</s>
<s>
The	O
BCL	B-Device
Molecular	I-Device
18	I-Device
was	O
a	O
group	O
of	O
systems	O
designed	O
and	O
manufactured	O
in	O
the	O
UK	O
in	O
the	O
1970s	O
and	O
1980s	O
.	O
</s>
<s>
The	O
NASA	O
Standard	O
Spacecraft	O
Computer	O
NSSC-1	B-Device
was	O
developed	O
as	O
a	O
standard	O
component	O
for	O
the	O
MultiMission	O
Modular	O
Spacecraft	O
at	O
the	O
Goddard	O
Space	O
Flight	O
Center	O
(	O
GSFC	O
)	O
in	O
1974	O
.	O
</s>
<s>
The	O
flying-spot	B-General_Concept
store	I-General_Concept
digital	O
memory	O
in	O
the	O
first	O
experimental	O
electronic	B-Device
switching	I-Device
systems	I-Device
used	O
nine	O
plates	O
of	O
optical	O
memory	O
that	O
were	O
read	O
and	O
written	O
two	O
bits	O
at	O
a	O
time	O
,	O
producing	O
a	O
word	O
size	O
of	O
18	B-General_Concept
bits	I-General_Concept
.	O
</s>
<s>
18-bit	B-General_Concept
machines	O
use	O
a	O
variety	O
of	O
character	O
encodings	O
.	O
</s>
<s>
The	O
DEC	O
Radix-50	O
,	O
called	O
Radix	O
508	O
format	O
,	O
packs	O
three	O
characters	O
plus	O
two	O
bits	O
in	O
each	O
18-bit	B-General_Concept
word	O
.	O
</s>
<s>
The	O
Teletype	O
packs	O
three	O
characters	O
in	O
each	O
18-bit	B-General_Concept
word	O
;	O
each	O
character	O
a	O
5-bit	O
Baudot	O
code	O
and	O
an	O
upper-case	O
bit	O
.	O
</s>
<s>
The	O
DEC	O
SIXBIT	O
format	O
packs	O
three	O
characters	O
in	O
each	O
18-bit	B-General_Concept
word	O
,	O
each	O
6-bit	O
character	O
obtained	O
by	O
stripping	O
the	O
high	O
bits	O
from	O
the	O
7-bit	B-Protocol
ASCII	I-Protocol
code	O
,	O
which	O
folds	O
lowercase	O
to	O
uppercase	O
letters	O
.	O
</s>
