<s>
The	O
HP	O
35s	O
(	O
F2215A	O
)	O
is	O
a	O
Hewlett-Packard	O
non-graphing	O
programmable	B-Application
scientific	O
calculator	O
.	O
</s>
<s>
Although	O
it	O
is	O
a	O
successor	O
to	O
the	O
HP	O
33s	O
,	O
it	O
was	O
introduced	O
to	O
commemorate	O
the	O
35th	O
anniversary	O
of	O
the	O
HP-35	B-Device
,	O
Hewlett-Packard	O
'	O
s	O
first	O
pocket	O
calculator	O
(	O
and	O
the	O
world	O
's	O
first	O
pocket	O
scientific	O
calculator	O
)	O
.	O
</s>
<s>
The	O
HP35s	B-Device
uses	O
either	O
Reverse	O
Polish	O
Notation	O
(	O
RPN	O
)	O
or	O
algebraic	O
infix	O
notation	O
as	O
input	O
.	O
</s>
<s>
Other	O
features	O
of	O
the	O
HP35s	B-Device
include	O
:	O
</s>
<s>
The	O
HP35s	B-Device
has	O
been	O
given	O
a	O
retro	O
look	O
reminiscent	O
of	O
classic	O
HP	B-Device
calculators	I-Device
from	O
the	O
1970s	O
to	O
the	O
1990s	O
.	O
</s>
<s>
The	O
physical	O
appearance	O
and	O
keyboard	O
layout	O
of	O
the	O
HP35s	B-Device
is	O
very	O
different	O
than	O
that	O
of	O
its	O
immediate	O
predecessor	O
,	O
the	O
HP33s	O
,	O
but	O
the	O
two	O
calculators	O
are	O
functionally	O
very	O
similar	O
.	O
</s>
<s>
The	O
HP35s	B-Device
allows	O
both	O
label	O
and	O
line	O
number	O
addressing	O
in	O
programs	O
.	O
</s>
<s>
The	O
memory	O
in	O
the	O
HP35s	B-Device
is	O
also	O
usable	O
for	O
data	O
storage	O
,	O
in	O
the	O
form	O
of	O
an	O
extra	O
801	O
numbered	O
memory	O
registers	O
.	O
</s>
<s>
Support	O
for	O
vector	O
operations	O
is	O
new	O
in	O
the	O
HP35s	B-Device
.	O
</s>
<s>
Indirect	O
branching	O
,	O
which	O
allows	O
the	O
contents	O
of	O
a	O
memory	O
register	O
to	O
be	O
used	O
as	O
the	O
target	O
of	O
a	O
branching	O
instruction	O
(	O
GTO	O
or	O
XEQ	O
)	O
is	O
omitted	O
from	O
the	O
HP35s	B-Device
.	O
</s>
<s>
HP	O
has	O
released	O
a	O
free-of-charge	B-License
35s	O
emulator	O
for	O
the	O
Windows	O
operating	O
system	O
(	O
and	O
Wine	B-Application
)	O
.	O
</s>
<s>
The	O
HP35s	B-Device
was	O
designed	O
by	O
Hewlett-Packard	O
in	O
conjunction	O
with	O
Kinpo	O
Electronics	O
of	O
Taiwan	O
,	O
which	O
manufactures	O
the	O
calculator	O
for	O
HP	O
in	O
mainland	O
China	O
.	O
</s>
<s>
The	O
case	O
features	O
many	O
design	O
elements	O
from	O
1970s	O
HP	B-Device
calculators	I-Device
such	O
as	O
the	O
ground-breaking	O
HP-65	B-Device
,	O
including	O
a	O
black	O
case	O
with	O
silver-striped	O
curved	O
sides	O
,	O
slope-fronted	O
keys	O
,	O
and	O
gold	O
and	O
blue	O
shift	O
keys	O
.	O
</s>
<s>
The	O
calculator	O
is	O
powered	O
by	O
two	O
CR2032	B-Algorithm
button	B-Algorithm
cells	I-Algorithm
connected	O
in	O
parallel	O
,	O
which	O
it	O
is	O
advised	O
to	O
replace	O
one	O
at	O
a	O
time	O
,	O
to	O
avoid	O
memory	O
loss	O
.	O
</s>
<s>
It	O
was	O
initially	O
supplied	O
with	O
a	O
hard	O
zippered	O
clamshell	O
case	O
with	O
a	O
pocket	O
for	O
notes	O
,	O
and	O
a	O
printed	O
manual	O
,	O
but	O
this	O
was	O
later	O
changed	O
to	O
a	O
slipcase	O
made	O
of	O
vinyl-covered	O
cardboard	O
with	O
elastic	O
sides	O
and	O
velvet	O
lining	O
,	O
and	O
a	O
CD-ROM	B-Device
containing	O
a	O
PDF	B-Application
manual	O
.	O
</s>
<s>
Several	O
firmware	O
bugs	B-Error_Name
have	O
also	O
been	O
reported	O
,	O
which	O
have	O
not	O
yet	O
been	O
fixed	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
the	O
US	O
,	O
it	O
is	O
the	O
most	O
powerful	O
programmable	B-Application
calculator	I-Application
approved	O
for	O
use	O
in	O
the	O
Fundamentals	O
of	O
Engineering	O
(	O
FE	O
)	O
and	O
Principles	O
and	O
Practice	O
of	O
Engineering	O
(	O
PE	O
)	O
examinations	O
.	O
</s>
<s>
Like	O
most	O
HP	B-Device
calculators	I-Device
,	O
it	O
defaults	O
to	O
RPN	O
.	O
</s>
<s>
In	O
RPN	O
mode	O
,	O
it	O
uses	O
a	O
four-level	O
stack	B-Application
,	O
as	O
have	O
all	O
HP	O
's	O
non-graphing	O
RPN	O
calculators	O
since	O
the	O
earliest	O
days	O
.	O
</s>
<s>
In	O
contrast	O
to	O
the	O
usual	O
computer-science	O
terminology	O
,	O
RPN	O
calculators	O
such	O
as	O
this	O
refer	O
to	O
the	O
operational	O
end	O
of	O
the	O
stack	B-Application
as	O
the	O
bottom	O
and	O
the	O
far	O
end	O
as	O
the	O
top	O
.	O
</s>
<s>
The	O
stack	B-Application
levels	O
are	O
named	O
X	O
(	O
the	O
bottom	O
)	O
,	O
Y	O
,	O
Z	O
,	O
and	O
T	O
(	O
the	O
top	O
)	O
;	O
they	O
have	O
no	O
connection	O
with	O
the	O
variables	O
of	O
the	O
same	O
names	O
.	O
</s>
<s>
Each	O
stack	B-Application
level	O
can	O
contain	O
any	O
of	O
the	O
data	O
types	O
supported	O
by	O
the	O
machine	O
:	O
real	O
number	O
,	O
complex	O
number	O
,	O
or	O
vector	O
.	O
</s>
<s>
Various	O
functions	O
are	O
provided	O
for	O
manipulating	O
the	O
stack	B-Application
,	O
such	O
as	O
and	O
to	O
roll	O
,	O
to	O
swap	O
X	O
and	O
Y	O
,	O
to	O
recall	O
the	O
last-used	O
X	O
value	O
,	O
and	O
to	O
swap	O
X	O
and	O
a	O
named	O
variable	O
.	O
</s>
<s>
The	O
expression	O
can	O
be	O
edited	O
using	O
the	O
arrow	B-Device
and	O
backspace	B-Device
keys	I-Device
,	O
and	O
re-evaluated	O
as	O
desired	O
.	O
</s>
<s>
Two	O
small	O
arrow	B-Device
symbols	O
on	O
the	O
display	O
indicate	O
if	O
the	O
actual	O
value	O
is	O
slightly	O
above	O
or	O
below	O
that	O
displayed	O
.	O
</s>
<s>
Previous	O
(	O
and	O
other	O
current	O
)	O
HP	B-Device
calculators	I-Device
have	O
handled	O
complex	O
numbers	O
in	O
a	O
variety	O
of	O
ways	O
.	O
</s>
<s>
In	O
the	O
HP33s	O
,	O
complex	O
numbers	O
were	O
stored	O
as	O
two	O
separate	O
values	O
,	O
and	O
the	O
"	O
complex	O
"	O
modifier	O
was	O
used	O
to	O
indicate	O
that	O
an	O
operation	O
was	O
to	O
treat	O
the	O
stack	B-Application
as	O
containing	O
complex	O
numbers	O
.	O
</s>
<s>
For	O
example	O
,	O
adding	O
and	O
involved	O
the	O
following	O
keystrokes	O
:	O
,	O
which	O
used	O
up	O
all	O
four	O
stack	B-Application
levels	O
.	O
</s>
<s>
For	O
example	O
,	O
directly	O
taking	O
the	O
square	O
root	O
of	O
a	O
negative	O
real	O
number	O
results	O
in	O
an	O
error	B-Error_Name
message	I-Error_Name
instead	O
of	O
a	O
complex	O
number	O
.	O
</s>
<s>
However	O
,	O
workarounds	B-Application
exist	O
for	O
many	O
of	O
those	O
limitations	O
.	O
</s>
<s>
A	O
vector	O
may	O
be	O
stored	O
on	O
the	O
stack	B-Application
,	O
or	O
in	O
any	O
variable	O
,	O
as	O
a	O
single	O
value	O
,	O
and	O
processed	O
by	O
various	O
functions	O
.	O
</s>
<s>
In	O
non-decimal	O
bases	O
,	O
the	O
word	O
length	O
is	O
fixed	O
at	O
36	O
bits	O
,	O
and	O
uses	O
two	B-General_Concept
's	I-General_Concept
complement	I-General_Concept
negation	O
.	O
</s>
<s>
Calculated	O
results	O
include	O
means	O
,	O
weighted	O
mean	O
,	O
standard	B-General_Concept
deviation	I-General_Concept
,	O
and	O
linear	B-General_Concept
regression	I-General_Concept
figures	O
.	O
</s>
<s>
Probability	O
functions	O
(	O
combinations	O
and	O
permutations	B-Algorithm
)	O
are	O
available	O
,	O
as	O
well	O
as	O
random	O
numbers	O
.	O
</s>
<s>
Equations	O
typically	O
include	O
named	O
variables	O
whose	O
values	O
are	O
to	O
be	O
supplied	O
by	O
the	O
user	O
at	O
run	O
time	O
,	O
but	O
can	O
also	O
take	O
values	O
from	O
the	O
stack	B-Application
.	O
</s>
<s>
Since	O
this	O
process	O
takes	O
time	O
,	O
and	O
the	O
equation	O
may	O
have	O
more	O
than	O
one	O
solution	O
,	O
it	O
is	O
guided	O
by	O
two	O
"	O
guesses	O
"	O
which	O
it	O
assumes	O
to	O
have	O
been	O
provided	O
by	O
the	O
user	O
,	O
in	O
the	O
stack	B-Application
's	O
X	O
register	O
,	O
and	O
in	O
the	O
variable	O
's	O
existing	O
value	O
.	O
</s>
<s>
The	O
user	O
first	O
places	O
the	O
two	O
interval	O
limits	O
on	O
the	O
stack	B-Application
,	O
then	O
selects	O
the	O
equation	O
and	O
the	O
function	O
,	O
which	O
prompts	O
for	O
the	O
name	O
of	O
the	O
variable	O
to	O
be	O
integrated	O
and	O
the	O
values	O
of	O
the	O
other	O
variables	O
.	O
</s>
<s>
The	O
HP35s	B-Device
is	O
keystroke-programmable	O
,	O
meaning	O
that	O
it	O
can	O
remember	O
and	O
later	O
execute	O
sequences	O
of	O
keystrokes	O
to	O
solve	O
particular	O
problems	O
of	O
interest	O
to	O
the	O
user	O
.	O
</s>
<s>
Program	O
keystrokes	O
are	O
fully	O
merged	O
:	O
functions	O
accessed	O
via	O
shift	O
keys	O
or	O
menus	O
are	O
recorded	O
as	O
one	O
keystroke	B-Device
,	O
not	O
two	O
or	O
more	O
.	O
</s>
<s>
These	O
keystroke	B-Device
programs	O
,	O
in	O
addition	O
to	O
performing	O
any	O
operation	O
normally	O
available	O
on	O
the	O
keyboard	O
,	O
can	O
also	O
make	O
use	O
of	O
conditional	O
and	O
unconditional	O
branching	O
and	O
looping	O
instructions	O
,	O
allowing	O
programs	O
to	O
perform	O
repetitive	O
operations	O
and	O
make	O
decisions	O
.	O
</s>
<s>
Within	O
the	O
program	O
space	O
,	O
up	O
to	O
twenty-six	O
alphabetic	O
labels	O
may	O
be	O
defined	O
in	O
the	O
form	O
,	O
and	O
each	O
label	O
may	O
be	O
followed	O
by	O
up	O
to	O
998	O
other	O
steps	O
,	O
so	O
that	O
any	O
step	O
may	O
be	O
targeted	O
by	O
a	O
(	O
"	O
go	B-Application
to	I-Application
"	O
)	O
or	O
(	O
"	O
execute	O
"	O
)	O
instruction	O
in	O
the	O
form	O
(	O
or	O
just	O
for	O
the	O
label	O
step	O
itself	O
,	O
A001	O
)	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
solving	O
,	O
the	O
program	O
is	O
treated	O
as	O
an	O
expression	O
whose	O
return	O
value	O
(	O
the	O
value	O
left	O
on	O
the	O
stack	B-Application
)	O
should	O
be	O
zero	O
.	O
</s>
