<s>
The	O
HP-35	B-Device
was	O
Hewlett-Packard	O
'	O
s	O
first	O
pocket	O
calculator	O
and	O
the	O
world	O
's	O
first	O
scientific	O
pocket	O
calculator	O
:	O
a	O
calculator	O
with	O
trigonometric	O
and	O
exponential	O
functions	O
.	O
</s>
<s>
In	O
about	O
1970	O
HP	O
co-founder	O
Bill	O
Hewlett	O
challenged	O
his	O
co-workers	O
to	O
create	O
a	O
"	O
shirt-pocket	O
sized	O
HP-9100	B-Device
"	O
.	O
</s>
<s>
Introduced	O
at	O
,	O
like	O
HP	O
's	O
first	O
scientific	O
calculator	O
,	O
the	O
desktop	O
9100A	B-Device
,	O
it	O
used	O
reverse	O
Polish	O
notation	O
(	O
RPN	O
)	O
rather	O
than	O
what	O
came	O
to	O
be	O
called	O
"	O
algebraic	O
"	O
entry	O
.	O
</s>
<s>
The	O
original	O
HP-35	B-Device
was	O
available	O
from	O
1972	O
to	O
1975	O
.	O
</s>
<s>
In	O
2007	O
HP	O
announced	O
the	O
release	O
of	O
the	O
"	O
retro	O
"	O
-look	O
HP	B-Device
35s	I-Device
to	O
commemorate	O
the	O
35th	O
anniversary	O
of	O
the	O
launch	O
of	O
the	O
original	O
HP-35	B-Device
.	O
</s>
<s>
The	O
HP-35	B-Device
was	O
named	O
an	O
IEEE	O
Milestone	O
in	O
2009	O
.	O
</s>
<s>
The	O
fifteen-digit	O
LED	O
display	O
was	O
capable	O
of	O
displaying	O
a	O
ten-digit	O
mantissa	B-Algorithm
plus	O
its	O
sign	O
and	O
a	O
decimal	O
point	O
and	O
a	O
two-digit	O
exponent	O
plus	O
its	O
sign	O
.	O
</s>
<s>
Replacement	O
battery	O
packs	O
are	O
no	O
longer	O
available	O
,	O
leaving	O
existing	O
HP-35	B-Device
calculators	O
to	O
rely	O
on	O
AC	O
power	O
,	O
or	O
their	O
users	O
to	O
rebuild	O
the	O
battery	O
packs	O
themselves	O
using	O
available	O
cells	O
.	O
</s>
<s>
Internally	O
,	O
the	O
calculator	O
was	O
organized	O
around	O
a	O
serial	O
(	O
1-bit	O
)	O
processor	O
chipset	B-Device
made	O
under	O
contract	O
by	O
Mostek	O
,	O
processing	O
56-bit	O
floating-point	B-Algorithm
numbers	I-Algorithm
,	O
representing	O
14-digit	O
BCD	O
numbers	O
.	O
</s>
<s>
The	O
calculator	O
had	O
a	O
four-register	O
stack	B-General_Concept
(	O
x	O
,	O
y	O
,	O
z	O
and	O
t	O
)	O
,	O
the	O
"	O
enter	O
"	O
key	O
pushed	O
the	O
displayed	O
value	O
(	O
x	O
)	O
down	O
the	O
stack	B-General_Concept
.	O
</s>
<s>
When	O
the	O
stack	B-General_Concept
was	O
popped	O
,	O
the	O
t	O
register	O
duplicated	O
into	O
the	O
z	O
register	O
.	O
</s>
<s>
The	O
HP-35	B-Device
was	O
the	O
start	O
of	O
a	O
family	O
of	O
related	O
calculators	O
with	O
similar	O
mechanical	O
packaging	O
:	O
</s>
<s>
The	O
HP-45	B-Device
added	O
many	O
more	O
features	O
,	O
including	O
the	O
ability	O
to	O
control	O
the	O
output	O
format	O
(	O
rather	O
than	O
the	O
purely	O
automatic	O
format	O
of	O
the	O
HP-35	B-Device
)	O
.	O
</s>
<s>
The	O
HP-65	B-Device
added	O
programmability	O
,	O
with	O
program	O
storage	O
on	O
magnetic	O
cards	O
.	O
</s>
<s>
The	O
HP-55	B-Device
,	O
a	O
less	O
expensive	O
follow-on	O
to	O
the	O
HP-65	B-Device
,	O
provided	O
storage	O
for	O
smaller	O
programs	O
,	O
but	O
did	O
n't	O
provide	O
any	O
external	O
storage	O
.	O
</s>
<s>
The	O
timer	O
that	O
was	O
already	O
present	O
on	O
the	O
HP-45	B-Device
was	O
now	O
crystal-controlled	O
to	O
achieve	O
the	O
needed	O
accuracy	O
and	O
explicitly	O
documented	O
.	O
</s>
<s>
The	O
HP-67	B-Device
expanded	O
on	O
the	O
programmability	O
of	O
the	O
HP-65	B-Device
,	O
and	O
added	O
fully	O
merged	O
keycodes	O
.	O
</s>
<s>
The	O
HP-25	B-Device
was	O
a	O
smaller	O
,	O
cheaper	O
model	O
of	O
a	O
programmable	O
scientific	O
calculator	O
without	O
magnetic	O
card	O
reader	O
,	O
with	O
features	O
much	O
like	O
the	O
HP-65	B-Device
.	O
</s>
<s>
The	O
HP-41C	B-Device
was	O
a	O
major	O
advance	O
in	O
programmability	O
and	O
capacity	O
,	O
and	O
offered	O
CMOS	B-Device
memory	I-Device
so	O
that	O
programs	O
were	O
not	O
lost	O
when	O
the	O
calculator	O
was	O
switched	O
off	O
.	O
</s>
<s>
Four	O
external	O
ports	O
below	O
the	O
display	O
area	O
allowed	O
memory	O
expansion	O
(	O
RAM	B-Architecture
modules	O
)	O
,	O
loading	O
of	O
additional	O
programs	O
(	O
ROM	B-Device
modules	O
)	O
and	O
interfacing	O
a	O
wide	O
variety	O
of	O
peripherals	O
including	O
HP-IL	B-Architecture
(	O
"	O
HP	O
Interface	O
Loop	O
"	O
)	O
,	O
a	O
scaled-down	O
version	O
of	O
the	O
HPIB/GPIB/IEEE	O
-488	O
instrument	O
bus	O
.	O
</s>
<s>
The	O
later	O
HP-28C	B-Device
and	O
HP-28S	B-Device
added	O
much	O
more	O
memory	O
and	O
a	O
substantially	O
different	O
,	O
more	O
powerful	O
programming	O
metaphor	O
.	O
</s>
<s>
The	O
HP-35	B-Device
was	O
long	O
and	O
wide	O
,	O
said	O
to	O
have	O
been	O
designed	O
to	O
fit	O
into	O
one	O
of	O
William	O
Hewlett	O
's	O
shirt	O
pockets	O
.	O
</s>
<s>
HP-35	B-Device
calculators	O
were	O
carried	O
on	O
the	O
Skylab	O
3	O
and	O
Skylab	O
4	O
flights	O
,	O
between	O
July	O
1973	O
and	O
February	O
1974	O
.	O
</s>
<s>
Is	O
the	O
first	O
pocket	O
calculator	O
with	O
a	O
numeric	B-Algorithm
range	O
that	O
covered	O
200	O
decades	O
(	O
more	O
precise	O
199	O
,	O
±10±99	O
)	O
.	O
</s>
<s>
The	O
LED	O
display	O
power	O
requirement	O
was	O
responsible	O
for	O
the	O
HP-35	B-Device
'	O
s	O
short	O
battery	O
life	O
between	O
charges	O
about	O
three	O
hours	O
.	O
</s>
<s>
The	O
HP-35	B-Device
calculated	O
arithmetic	O
,	O
logarithmic	O
,	O
and	O
trigonometric	O
functions	O
but	O
the	O
complete	O
implementation	O
used	O
only	O
767	O
carefully	O
chosen	O
instructions	O
(	O
7670	O
bits	O
)	O
.	O
</s>
<s>
One	O
high	O
quality	O
feature	O
of	O
the	O
HP-35	B-Device
was	O
its	O
use	O
of	O
double-injected	O
keys	O
.	O
</s>
<s>
Introduction	O
of	O
the	O
HP-35	B-Device
and	O
similar	O
scientific	O
calculators	O
by	O
Texas	O
Instruments	O
soon	O
thereafter	O
signaled	O
the	O
demise	O
of	O
the	O
slide	O
rule	O
among	O
science	O
and	O
engineering	O
students	O
.	O
</s>
<s>
100,000	O
HP-35	B-Device
calculators	O
were	O
sold	O
in	O
the	O
first	O
year	O
,	O
and	O
over	O
300,000	O
by	O
the	O
time	O
it	O
was	O
discontinued	O
in	O
1975	O
—	O
3½	O
years	O
after	O
its	O
introduction	O
.	O
</s>
