<s>
The	O
PDP-5	B-Device
was	O
Digital	O
Equipment	O
Corporation	O
's	O
first	O
12-bit	B-Device
computer	O
,	O
introduced	O
in	O
1963	O
.	O
</s>
<s>
An	O
earlier	O
12-bit	B-Device
computer	O
,	O
named	O
LINC	B-Device
has	O
been	O
described	O
as	O
the	O
first	O
minicomputer	B-Architecture
and	O
also	O
"	O
the	O
first	O
modern	O
personal	O
computer.	O
"	O
</s>
<s>
It	O
had	O
2,048	O
12-bit	B-Device
words	O
,	O
and	O
the	O
first	O
LINC	B-Device
was	O
built	O
in	O
1962	O
.	O
</s>
<s>
DEC	O
's	O
founder	O
,	O
Ken	O
Olsen	O
,	O
had	O
worked	O
with	O
both	O
it	O
and	O
a	O
still	O
earlier	O
computer	O
,	O
the	O
18-bit	B-General_Concept
64,000	O
-word	O
TX-0	B-Device
,	O
at	O
MIT	O
's	O
Lincoln	O
Laboratory	O
.	O
</s>
<s>
Although	O
the	O
LINC	B-Device
computer	O
was	O
intended	O
primarily	O
for	O
laboratory	O
use	O
,	O
the	O
PDP-5	B-Device
'	O
s	O
12-bit	B-Device
system	O
had	O
a	O
far	O
wider	O
range	O
of	O
use	O
.	O
</s>
<s>
"	O
A	O
PDP-5	B-Device
computer	O
was	O
used	O
very	O
successfully	O
aboard	O
Evergreen	O
for	O
...	O
"	O
</s>
<s>
all	O
of	O
which	O
described	O
the	O
same	O
PDP-5	B-Device
used	O
by	O
the	O
United	O
States	O
Coast	O
Guard	O
.	O
</s>
<s>
The	O
principal	O
designer	O
of	O
the	O
PDP-5	B-Device
was	O
the	O
young	O
engineer	O
Edson	O
de	O
Castro	O
who	O
went	O
on	O
later	O
to	O
found	O
Data	O
General	O
.	O
</s>
<s>
By	O
contrast	O
with	O
the	O
4-cabinet	O
PDP-1	B-Device
,	O
the	O
minimum	O
configuration	O
of	O
the	O
PDP-5	B-Device
was	O
a	O
single	O
19-inch	O
cabinet	O
with	O
"	O
150	O
printed	O
circuit	O
board	O
modules	O
holding	O
over	O
900	O
transistors.	O
"	O
</s>
<s>
The	O
machine	O
was	O
offered	O
with	O
from	O
1,024	O
to	O
32,768	O
12-bit	B-Device
words	O
of	O
core	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Addressing	O
more	O
than	O
4,096	O
words	O
of	O
memory	O
required	O
the	O
addition	O
of	O
a	O
Type	O
154	O
Memory	O
Extension	O
Control	O
unit	O
(	O
in	O
modern	O
terms	O
,	O
a	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
)	O
;	O
this	O
allowed	O
adding	O
additional	O
Type	O
155	O
4,096	O
word	O
core	B-General_Concept
memory	I-General_Concept
modules	O
.	O
</s>
<s>
Of	O
the	O
12	B-Device
bits	I-Device
in	O
each	O
word	O
,	O
exactly	O
3	O
were	O
used	O
for	O
instruction	O
op-codes	O
.	O
</s>
<s>
The	O
PDP-5	B-Device
'	O
s	O
instruction	O
set	O
was	O
later	O
expanded	O
in	O
its	O
successor	O
,	O
the	O
PDP-8	B-Device
.	O
</s>
<s>
The	O
biggest	O
change	O
was	O
that	O
,	O
in	O
the	O
PDP-5	B-Device
,	O
the	O
program	O
counter	O
was	O
stored	O
in	O
memory	O
location	O
zero	O
,	O
while	O
on	O
PDP-8	B-Device
computers	O
,	O
it	O
was	O
a	O
register	O
inside	O
the	O
CPU	O
.	O
</s>
<s>
Another	O
significant	O
change	O
was	O
that	O
microcoded	O
instructions	O
on	O
the	O
PDP-5	B-Device
could	O
not	O
combine	O
incrementing	O
and	O
clearing	O
the	O
accumulator	O
,	O
while	O
these	O
could	O
be	O
combined	O
on	O
the	O
PDP-8	B-Device
.	O
</s>
<s>
This	O
allowed	O
loading	O
of	O
many	O
small	O
constants	O
in	O
a	O
single	O
instruction	O
on	O
the	O
PDP-8	B-Device
.	O
</s>
<s>
The	O
PDP-5	B-Device
was	O
one	O
of	O
the	O
first	O
computer	O
series	O
with	O
more	O
than	O
1,000	O
built	O
.	O
</s>
<s>
DDT	B-Operating_System
(	O
a	O
debugger	B-Application
)	O
.	O
</s>
<s>
With	O
a	O
base	O
price	O
of	O
$	O
27,000	O
and	O
designed	O
for	O
those	O
not	O
in	O
need	O
of	O
the	O
18-bit	B-General_Concept
PDP-4	B-Device
,	O
yet	O
having	O
"	O
applications	O
needing	O
solutions	O
too	O
complicated	O
to	O
be	O
solved	O
efficiently	O
by	O
modules	O
systems	O
"	O
the	O
PDP-5	B-Device
,	O
when	O
introduced	O
in	O
1963	O
,	O
came	O
at	O
a	O
time	O
when	O
the	O
minicomputer	B-Architecture
market	O
was	O
gaining	O
a	O
foothold	O
.	O
</s>
