<s>
The	O
Harvard	B-Device
Mark	I-Device
II	I-Device
,	O
also	O
known	O
as	O
the	O
Aiken	O
Relay	O
Calculator	O
,	O
was	O
an	O
electromechanical	O
computer	O
built	O
under	O
the	O
direction	O
of	O
Howard	O
Aiken	O
at	O
Harvard	O
University	O
,	O
completed	O
in	O
1947	O
.	O
</s>
<s>
The	O
contract	O
to	O
build	O
the	O
Mark	O
II	O
was	O
signed	O
with	O
Harvard	O
in	O
February	O
1945	O
,	O
after	O
the	O
successful	O
demonstration	O
of	O
the	O
Mark	B-Device
I	I-Device
in	O
1944	O
.	O
</s>
<s>
The	O
Mark	O
II	O
was	O
constructed	O
with	O
high-speed	O
electromagnetic	O
relays	O
instead	O
of	O
the	O
electro-mechanical	O
counters	O
used	O
in	O
the	O
Mark	B-Device
I	I-Device
,	O
making	O
it	O
much	O
faster	O
than	O
its	O
predecessor	O
.	O
</s>
<s>
This	O
was	O
a	O
factor	O
of	O
2.6	O
faster	O
for	O
addition	O
and	O
a	O
factor	O
of	O
8	O
faster	O
for	O
multiplication	O
compared	O
to	O
the	O
Mark	B-Device
I	I-Device
.	O
</s>
<s>
The	O
Mark	B-Device
I	I-Device
and	O
Mark	O
II	O
were	O
not	O
stored-program	O
computers	O
–	O
they	O
read	O
instructions	B-General_Concept
of	O
the	O
program	O
one	O
at	O
a	O
time	O
from	O
a	O
tape	O
and	O
executed	O
them	O
.	O
</s>
<s>
This	O
separation	O
of	O
data	O
and	O
instructions	B-General_Concept
is	O
known	O
as	O
the	O
Harvard	B-Architecture
architecture	I-Architecture
.	O
</s>
<s>
The	O
tape	O
containing	O
the	O
program	O
could	O
encode	O
only	O
eight	O
instructions	B-General_Concept
,	O
so	O
what	O
a	O
particular	O
instruction	O
code	O
meant	O
depended	O
on	O
when	O
it	O
was	O
executed	O
.	O
</s>
