<s>
The	O
JOHNNIAC	B-Device
was	O
an	O
early	O
computer	O
built	O
by	O
the	O
RAND	O
Corporation	O
(	O
not	O
Remington	O
Rand	O
,	O
maker	O
of	O
the	O
contemporaneous	O
UNIVAC	B-Operating_System
I	I-Operating_System
computer	O
)	O
and	O
based	O
on	O
the	O
von	B-Architecture
Neumann	I-Architecture
architecture	I-Architecture
that	O
had	O
been	O
pioneered	O
on	O
the	O
IAS	B-Device
machine	I-Device
.	O
</s>
<s>
JOHNNIAC	B-Device
is	O
arguably	O
the	O
longest	O
operational	O
early	O
computer	O
,	O
being	O
used	O
almost	O
continuously	O
from	O
1953	O
for	O
over	O
13	O
years	O
before	O
finally	O
being	O
shut	O
down	O
on	O
February	O
11	O
,	O
1966	O
,	O
logging	O
over	O
50,000	O
operating	O
hours	O
.	O
</s>
<s>
Like	O
the	O
IAS	B-Device
machine	I-Device
,	O
JOHNNIAC	B-Device
used	O
40-bit	O
words	O
,	O
and	O
included	O
1024	O
words	O
of	O
Selectron	O
tube	O
main	O
memory	O
,	O
each	O
holding	O
256	O
bits	O
of	O
data	O
.	O
</s>
<s>
There	O
were	O
no	O
index	B-General_Concept
registers	I-General_Concept
,	O
and	O
as	O
addresses	O
were	O
stored	O
in	O
the	O
instructions	O
,	O
loops	O
had	O
to	O
be	O
implemented	O
by	O
modifying	O
the	O
instructions	O
as	O
the	O
program	O
ran	O
.	O
</s>
<s>
JOHNNIAC	B-Device
weighed	O
.	O
</s>
<s>
Later	O
in	O
1955	O
a	O
12k-word	O
drum	B-General_Concept
memory	I-General_Concept
secondary	O
storage	O
system	O
was	O
added	O
as	O
well	O
.	O
</s>
<s>
A	O
transistor-based	O
adder	O
replaced	O
the	O
original	O
tube-based	O
adder	O
in	O
1956	O
.	O
</s>
<s>
Numerous	O
changes	O
were	O
made	O
to	O
the	O
input/output	B-General_Concept
peripherals	O
as	O
well	O
,	O
and	O
in	O
1964	O
,	O
a	O
real-time	O
clock	O
was	O
added	O
to	O
support	O
time-sharing	B-General_Concept
.	O
</s>
<s>
One	O
JOHNNIAC	B-Device
legacy	O
was	O
the	O
JOSS	B-Language
programming	I-Language
language	I-Language
(	O
the	O
JOHNNIAC	B-Language
Open	I-Language
Shop	I-Language
System	I-Language
)	O
,	O
an	O
easy-to-use	O
language	O
which	O
catered	O
to	O
novices	O
.	O
</s>
<s>
JOSS	B-Language
was	O
an	O
ancestor	O
of	O
DEC	O
's	O
FOCAL	B-Language
and	O
of	O
MUMPS	B-Language
.	O
</s>
<s>
The	O
CYCLONE	B-Device
at	O
Iowa	O
State	O
University	O
was	O
a	O
direct	O
clone	O
of	O
JOHNNIAC	B-Device
,	O
and	O
was	O
instruction	O
compatible	O
with	O
it	O
(	O
the	O
ILLIAC	B-Device
I	I-Device
may	O
have	O
been	O
as	O
well	O
)	O
.	O
</s>
<s>
Cyclone	B-Device
was	O
later	O
updated	O
to	O
include	O
a	O
hardware	O
for	O
floating-point	B-Algorithm
arithmetic	I-Algorithm
.	O
</s>
