<s>
The	O
LGP-30	B-Device
,	O
standing	O
for	O
Librascope	O
General	O
Purpose	O
and	O
then	O
Librascope	O
General	O
Precision	O
,	O
was	O
an	O
early	O
off-the-shelf	O
computer	O
.	O
</s>
<s>
The	O
LGP-30	B-Device
was	O
first	O
manufactured	O
in	O
1956	O
,	O
at	O
a	O
retail	O
price	O
of	O
$47	O
,	O
000	O
,	O
.	O
</s>
<s>
The	O
LGP-30	B-Device
was	O
commonly	O
referred	O
to	O
as	O
a	O
desk	O
computer	O
.	O
</s>
<s>
The	O
primary	O
design	O
consultant	O
for	O
the	O
Librascope	O
computer	O
was	O
Stan	O
Frankel	O
,	O
a	O
Manhattan	O
Project	O
veteran	O
and	O
one	O
of	O
the	O
first	O
programmers	O
of	O
ENIAC	B-Device
.	O
</s>
<s>
The	O
single	O
address	O
instruction	B-General_Concept
set	I-General_Concept
had	O
only	O
16	O
commands	O
.	O
</s>
<s>
Magnetic	B-General_Concept
drum	I-General_Concept
memory	I-General_Concept
held	O
the	O
main	O
memory	O
,	O
and	O
the	O
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
(	O
CPU	O
)	O
processor	B-General_Concept
registers	I-General_Concept
,	O
timing	O
information	O
,	O
and	O
the	O
master	O
bit	O
clock	O
,	O
each	O
on	O
a	O
dedicated	O
track	O
.	O
</s>
<s>
The	O
number	O
of	O
vacuum	O
tubes	O
was	O
minimized	O
by	O
using	O
solid-state	O
diode	B-General_Concept
logic	I-General_Concept
,	O
a	O
bit-serial	B-General_Concept
architecture	I-General_Concept
and	O
multiple	O
use	O
of	O
each	O
of	O
the	O
15	O
flip-flops	O
.	O
</s>
<s>
It	O
was	O
a	O
binary	O
,	O
31-bit	O
word	O
computer	O
with	O
a	O
4096-word	O
drum	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Standard	O
inputs	O
were	O
the	O
Flexowriter	B-Application
keyboard	O
and	O
paper	O
tape	O
(	O
ten	O
six-bit	O
characters/second	O
)	O
.	O
</s>
<s>
The	O
standard	O
output	O
was	O
the	O
Flexowriter	B-Application
printer	O
(	O
typewriter	O
,	O
working	O
at	O
10	O
characters/second	O
)	O
.	O
</s>
<s>
680	O
of	O
the	O
1450	O
diodes	O
were	O
mounted	O
on	O
one	O
pluggable	O
logic	B-Device
board	I-Device
.	O
</s>
<s>
The	O
LGP-30	B-Device
required	O
1500	O
watts	O
operating	O
under	O
full	O
load	O
.	O
</s>
<s>
No	O
expensive	O
air	O
conditioning	O
was	O
necessary	O
if	O
the	O
LGP-30	B-Device
was	O
operated	O
at	O
reasonable	O
temperatures	O
.	O
</s>
<s>
The	O
LGP-30	B-Device
provided	O
for	O
operand-location	O
optimization	O
by	O
interleaving	B-Application
the	O
logical	O
addresses	O
on	O
the	O
drum	O
so	O
that	O
two	O
adjacent	O
addresses	O
(	O
e.g.	O
,	O
00	O
and	O
01	O
)	O
were	O
separated	O
by	O
nine	O
physical	O
locations	O
.	O
</s>
<s>
The	O
unused	O
half	O
could	O
have	O
been	O
used	O
for	O
extra	O
instructions	O
,	O
indexing	O
,	O
indirect	B-Language
addressing	I-Language
,	O
or	O
a	O
second	O
( +1	O
)	O
address	O
to	O
locate	O
the	O
next	O
instruction	O
,	O
each	O
of	O
which	O
would	O
have	O
increased	O
program	O
performance	O
.	O
</s>
<s>
None	O
of	O
these	O
features	O
were	O
implemented	O
in	O
the	O
LGP-30	B-Device
,	O
but	O
some	O
were	O
realized	O
in	O
its	O
1960	O
successor	O
,	O
the	O
RPC-4000	O
.	O
</s>
<s>
A	O
unique	O
feature	O
of	O
the	O
LGP-30	B-Device
was	O
its	O
built-in	O
multiplication	O
,	O
despite	O
being	O
inexpensive	O
.	O
</s>
<s>
To	O
further	O
reduce	O
costs	O
,	O
the	O
traditional	O
front	B-Device
panel	I-Device
lights	O
showing	O
internal	O
registers	O
were	O
absent	O
.	O
</s>
<s>
Instead	O
,	O
Librascope	O
mounted	O
a	O
small	O
oscilloscope	O
on	O
the	O
front	B-Device
panel	I-Device
that	O
displayed	O
the	O
output	O
from	O
the	O
three	O
register	O
read	O
heads	O
,	O
one	O
above	O
the	O
other	O
,	O
allowing	O
the	O
operator	O
to	O
see	O
and	O
read	O
the	O
bits	O
.	O
</s>
<s>
Arithmetic	O
element	O
:	O
three	O
working	B-General_Concept
registers	I-General_Concept
:	O
C	O
the	O
counter	O
register	O
,	O
R	O
the	O
instruction	O
register	O
and	O
A	O
the	O
accumulator	O
register	O
.	O
</s>
<s>
Achievements	O
:	O
The	O
LGP-30	B-Device
was	O
one	O
of	O
the	O
first	O
desk-sized	O
computers	O
offering	O
small	O
scale	O
scientific	O
computing	O
.	O
</s>
<s>
The	O
LGP-30	B-Device
was	O
fairly	O
popular	O
with	O
"	O
half	O
a	O
thousand	O
"	O
units	O
sold	O
,	O
including	O
one	O
to	O
Dartmouth	O
College	O
where	O
students	O
implemented	O
Dartmouth	B-Language
ALGOL	I-Language
30	I-Language
and	O
DOPE	B-Language
(	O
Dartmouth	O
Oversimplified	O
Programming	O
Experiment	O
)	O
on	O
the	O
machine	O
.	O
</s>
<s>
The	O
LGP-30	B-Device
had	O
a	O
high-level	O
language	O
called	O
ACT-III	O
.	O
</s>
<s>
Dartmouth	O
College	O
developed	O
two	O
implementations	O
of	O
ALGOL	B-Language
60	I-Language
for	O
the	O
LGP-30	B-Device
.	O
</s>
<s>
Dartmouth	B-Language
ALGOL	I-Language
30	I-Language
was	O
a	O
three-pass	O
system	O
(	O
compiler	O
,	O
loader	O
,	O
and	O
interpreter	O
)	O
that	O
provided	O
almost	O
all	O
features	O
of	O
ALGOL	O
except	O
those	O
requiring	O
run-time	O
storage	O
allocation	O
.	O
</s>
<s>
The	O
procedure	O
for	O
starting	O
,	O
or	O
"	O
booting	B-Operating_System
"	O
the	O
LGP-30	B-Device
was	O
one	O
of	O
the	O
most	O
complicated	O
ever	O
devised	O
.	O
</s>
<s>
First	O
,	O
the	O
bootstrap	O
paper	O
tape	O
was	O
snapped	O
into	O
the	O
console	O
typewriter	O
,	O
a	O
Friden	B-Application
Flexowriter	I-Application
.	O
</s>
<s>
The	O
operator	O
pressed	O
a	O
lever	O
on	O
the	O
Flexowriter	B-Application
to	O
read	O
an	O
address	O
field	O
and	O
pressed	O
a	O
button	O
on	O
the	O
front	B-Device
panel	I-Device
to	O
transfer	O
the	O
address	O
into	O
a	O
computer	O
register	O
.	O
</s>
<s>
Then	O
the	O
lever	O
on	O
the	O
Flexowriter	B-Application
was	O
pressed	O
to	O
read	O
the	O
data	O
field	O
and	O
three	O
more	O
buttons	O
were	O
pressed	O
on	O
the	O
front	B-Device
panel	I-Device
to	O
store	O
it	O
at	O
the	O
specified	O
address	O
.	O
</s>
<s>
The	O
operator	O
then	O
removed	O
the	O
bootstrap	O
tape	O
,	O
snapped	O
in	O
the	O
tape	O
containing	O
the	O
regular	O
loader	O
,	O
carefully	O
arranging	O
it	O
so	O
it	O
would	O
not	O
jam	O
,	O
and	O
pressed	O
a	O
few	O
more	O
buttons	O
to	O
start	O
up	O
the	O
bootstrap	B-Operating_System
program	I-Operating_System
.	O
</s>
<s>
The	O
regular	O
loader	O
read	O
a	O
more	O
compact	O
format	O
tape	O
than	O
the	O
bootstrap	B-Operating_System
loader	I-Operating_System
.	O
</s>
<s>
In	O
1963	O
,	O
Librascope	O
produced	O
a	O
transistorized	O
update	O
to	O
the	O
LGP-30	B-Device
named	O
the	O
LGP-21	O
.	O
</s>
<s>
Similar	O
to	O
the	O
LGP-30	B-Device
,	O
but	O
transistorized	O
,	O
it	O
featured	O
8,008	O
32-bit	O
words	O
of	O
memory	B-General_Concept
drum	I-General_Concept
storage	O
.	O
</s>
<s>
Edward	O
Lorenz	O
used	O
the	O
LGP-30	B-Device
in	O
his	O
attempt	O
to	O
model	O
changing	O
weather	O
patterns	O
.	O
</s>
<s>
The	O
RPC-4000	O
(	O
successor	O
to	O
the	O
LGP-30	B-Device
)	O
is	O
also	O
remembered	O
as	O
the	O
computer	O
on	O
which	O
Mel	O
Kaye	O
performed	O
a	O
legendary	O
programming	O
task	O
in	O
machine	B-Language
code	I-Language
,	O
retold	O
by	O
Ed	O
Nather	O
in	O
the	O
hacker	O
epic	O
The	O
Story	O
of	O
Mel	O
.	O
</s>
