<s>
The	O
PDP-9	B-Device
,	O
the	O
fourth	O
of	O
the	O
five	O
18-bit	O
minicomputers	B-Architecture
produced	O
by	O
Digital	O
Equipment	O
Corporation	O
,	O
was	O
introduced	O
in	O
1966	O
.	O
</s>
<s>
A	O
total	O
of	O
445	O
PDP-9	B-Device
systems	O
were	O
produced	O
,	O
of	O
which	O
40	O
were	O
the	O
compact	O
,	O
low-cost	O
PDP-9/L	O
units	O
.	O
</s>
<s>
The	O
18-bit	O
PDP	O
systems	O
preceding	O
the	O
PDP-9	B-Device
were	O
the	O
PDP-1	B-Device
,	O
PDP-4	B-Device
and	O
PDP-7	B-Device
.	O
</s>
<s>
Its	O
successor	O
was	O
the	O
PDP-15	B-Device
.	O
</s>
<s>
The	O
PDP-9	B-Device
,	O
which	O
was	O
"	O
two	O
metres	O
wide	O
and	O
about	O
75cm	O
deep	O
,	O
"	O
was	O
approximately	O
twice	O
the	O
speed	O
of	O
the	O
PDP-7	B-Device
.	O
</s>
<s>
The	O
PDP-9	B-Device
weighed	O
about	O
and	O
the	O
PDP-9/L	O
weighed	O
about	O
.	O
</s>
<s>
Among	O
the	O
improvements	O
of	O
the	O
PDP-9	B-Device
over	O
its	O
PDP-7	B-Device
predecessor	O
were	O
:	O
</s>
<s>
User/university	O
-based	O
research	O
projects	O
for	O
extending	O
the	O
PDP-9	B-Device
included	O
:	O
</s>
<s>
DECsys	O
,	O
provided	O
an	O
interactive	O
,	O
single	O
user	O
,	O
program	O
development	O
environment	O
for	O
Fortran	B-Application
and	O
assembly	O
language	O
programs	O
.	O
</s>
<s>
Both	O
FORTRAN	B-Application
II	O
and	O
FORTRAN	B-Application
IV	O
were	O
implemented	O
for	O
the	O
PDP-9	B-Device
.	O
</s>
<s>
MUMPS	B-Language
was	O
originally	O
developed	O
on	O
the	O
PDP-7	B-Device
,	O
and	O
ran	O
on	O
several	O
PDP-9s	B-Device
at	O
the	O
Massachusetts	O
General	O
Hospital	O
.	O
</s>
<s>
The	O
PDP-7	B-Device
,	O
of	O
which	O
120	O
were	O
sold	O
,	O
was	O
described	O
as	O
"	O
highly	O
successful.	O
"	O
.	O
</s>
<s>
The	O
PDP-9	B-Device
sold	O
445	O
units	O
.	O
</s>
<s>
Both	O
had	O
submodels	O
,	O
the	O
PDP-7A	O
and	O
the	O
PDP-9/L	O
,	O
neither	O
of	O
which	O
accounted	O
for	O
a	O
substantial	O
percentage	O
of	O
sales	O
.	O
</s>
