<s>
The	O
Z1	B-Device
was	O
a	O
motor-driven	O
mechanical	B-Device
computer	I-Device
designed	O
by	O
Konrad	O
Zuse	O
from	O
1936	O
to	O
1937	O
,	O
which	O
he	O
built	O
in	O
his	O
parents	O
 '	O
home	O
from	O
1936	O
to	O
1938	O
.	O
</s>
<s>
The	O
“	O
Z1	B-Device
”	O
was	O
the	O
first	O
freely	O
programmable	B-General_Concept
computer	O
in	O
the	O
world	O
which	O
used	O
Boolean	O
logic	O
and	O
binary	B-Algorithm
floating-point	I-Algorithm
numbers	I-Algorithm
,	O
however	O
it	O
was	O
unreliable	O
in	O
operation	O
.	O
</s>
<s>
The	O
Z1	B-Device
was	O
the	O
first	O
in	O
a	O
series	O
of	O
computers	O
that	O
Zuse	O
designed	O
.	O
</s>
<s>
After	O
WW2	O
,	O
it	O
was	O
renamed	O
"	O
Z1	B-Device
"	O
to	O
differentiate	O
from	O
the	O
flying	O
bombs	O
designed	O
by	O
Robert	O
Lusser	O
.	O
</s>
<s>
The	O
Z2	B-Device
and	O
Z3	B-Device
were	O
follow-ups	O
based	O
on	O
many	O
of	O
the	O
same	O
ideas	O
as	O
the	O
Z1	B-Device
.	O
</s>
<s>
The	O
Z1	B-Device
contained	O
almost	O
all	O
the	O
parts	O
of	O
a	O
modern	O
computer	O
,	O
i.e.	O
</s>
<s>
control	O
unit	O
,	O
memory	O
,	O
micro	O
sequences	O
,	O
floating-point	B-Algorithm
logic	O
,	O
and	O
input-output	O
devices	O
.	O
</s>
<s>
The	O
Z1	B-Device
was	O
freely	O
programmable	B-General_Concept
via	O
punched	O
tape	O
and	O
a	O
punched	O
tape	O
reader	O
.	O
</s>
<s>
The	O
Z1	B-Device
was	O
a	O
22-bit	O
floating-point	B-Algorithm
value	O
adder	O
and	O
subtractor	O
,	O
with	O
some	O
control	O
logic	O
to	O
make	O
it	O
capable	O
of	O
more	O
complex	O
operations	O
such	O
as	O
multiplication	O
(	O
by	O
repeated	O
additions	O
)	O
and	O
division	O
(	O
by	O
repeated	O
subtractions	O
)	O
.	O
</s>
<s>
The	O
Z1	B-Device
's	O
instruction	B-General_Concept
set	I-General_Concept
had	O
eight	O
instructions	O
and	O
it	O
took	O
between	O
one	O
and	O
twenty	O
one	O
cycles	O
per	O
instruction	O
.	O
</s>
<s>
The	O
Z1	B-Device
had	O
a	O
16-word	O
floating	B-Algorithm
point	I-Algorithm
memory	O
,	O
where	O
each	O
word	O
of	O
memory	O
could	O
be	O
read	O
from	O
–	O
and	O
written	O
to	O
–	O
the	O
control	O
unit	O
.	O
</s>
<s>
The	O
input	O
and	O
output	O
instructions	O
would	O
be	O
read	O
or	O
written	O
as	O
floating-point	B-Algorithm
numbers	I-Algorithm
.	O
</s>
<s>
"	O
Z1	B-Device
was	O
a	O
machine	O
weighing	O
about	O
1	O
tonne	O
in	O
weight	O
,	O
which	O
consisted	O
of	O
some	O
20,000	O
parts	O
.	O
</s>
<s>
It	O
was	O
a	O
programmable	B-General_Concept
computer	O
,	O
based	O
on	O
binary	B-Algorithm
floating-point	I-Algorithm
numbers	I-Algorithm
and	O
a	O
binary	O
switching	O
system	O
.	O
</s>
<s>
Construction	O
of	O
the	O
Z1	B-Device
was	O
privately	O
financed	O
.	O
</s>
<s>
Zuse	O
constructed	O
the	O
Z1	B-Device
in	O
his	O
parents	O
 '	O
apartment	O
;	O
in	O
fact	O
,	O
he	O
was	O
allowed	O
to	O
use	O
the	O
living	O
room	O
for	O
his	O
construction	O
.	O
</s>
<s>
In	O
1936	O
,	O
Zuse	O
quit	O
his	O
job	O
in	O
airplane	O
construction	O
in	O
order	O
to	O
build	O
the	O
Z1	B-Device
.	O
</s>
<s>
Zuse	O
is	O
said	O
to	O
have	O
used	O
"	O
thin	O
metal	O
strips	O
"	O
and	O
perhaps	O
"	O
metal	O
cylinders	O
"	O
or	O
glass	O
plates	O
to	O
construct	O
Z1	B-Device
.	O
</s>
<s>
There	O
were	O
probably	O
no	O
commercial	O
relays	O
in	O
it	O
(	O
though	O
the	O
Z3	B-Device
is	O
said	O
to	O
have	O
used	O
a	O
few	O
telephone	O
relays	O
)	O
.	O
</s>
<s>
The	O
Z2	B-Device
used	O
the	O
mechanical	O
memory	O
of	O
the	O
Z1	B-Device
,	O
but	O
used	O
relay-based	O
arithmetic	O
.	O
</s>
<s>
The	O
Z3	B-Device
was	O
experimentally	O
built	O
entirely	O
of	O
relays	O
.	O
</s>
<s>
The	O
Z4	B-Device
was	O
the	O
first	O
attempt	O
at	O
a	O
commercial	O
computer	O
,	O
reverting	O
to	O
the	O
faster	O
and	O
more	O
economical	O
mechanical	O
slotted	O
metal	O
strip	O
memory	O
,	O
with	O
relay	O
processing	O
,	O
of	O
the	O
Z2	B-Device
,	O
but	O
the	O
war	O
interrupted	O
the	O
Z4	B-Device
development.	O
'	O
</s>
<s>
The	O
Z1	B-Device
was	O
never	O
very	O
reliable	O
in	O
operation	O
because	O
of	O
poor	O
synchronization	O
caused	O
by	O
internal	O
and	O
external	O
stresses	O
on	O
the	O
mechanical	O
parts	O
.	O
</s>
<s>
The	O
original	O
Z1	B-Device
was	O
destroyed	O
by	O
the	O
Allied	O
air	O
raids	O
in	O
1943	O
,	O
but	O
in	O
the	O
1980s	O
Zuse	O
decided	O
to	O
rebuild	O
the	O
machine	O
.	O
</s>
<s>
The	O
first	O
sketches	O
of	O
the	O
Z1	B-Device
reconstruction	O
were	O
drawn	O
in	O
1984	O
.	O
</s>
<s>
He	O
constructed	O
(	O
with	O
the	O
help	O
of	O
two	O
engineering	O
students	O
)	O
thousands	O
of	O
elements	O
of	O
the	O
Z1	B-Device
again	O
,	O
and	O
finished	O
rebuilding	O
the	O
device	O
in	O
1989	O
.	O
</s>
<s>
The	O
rebuilt	O
Z1	B-Device
(	O
pictured	O
)	O
is	O
displayed	O
at	O
the	O
German	O
Museum	O
of	O
Technology	O
in	O
Berlin	O
.	O
</s>
