<s>
The	O
HP-42S	B-Device
RPN	I-Device
Scientific	I-Device
is	O
a	O
programmable	B-Application
RPN	O
Scientific	O
hand	O
held	O
calculator	O
introduced	O
by	O
Hewlett	O
Packard	O
in	O
1988	O
.	O
</s>
<s>
It	O
has	O
advanced	O
functions	O
suitable	O
for	O
applications	O
in	O
mathematics	O
,	O
linear	B-Language
algebra	I-Language
,	O
statistical	O
analysis	O
,	O
computer	B-General_Concept
science	I-General_Concept
and	O
others	O
.	O
</s>
<s>
Perhaps	O
the	O
HP-42S	B-Device
was	O
to	O
be	O
released	O
as	O
a	O
replacement	O
for	O
the	O
aging	O
HP-41	B-Device
series	O
as	O
it	O
is	O
designed	O
to	O
be	O
compatible	O
with	O
all	O
programs	O
written	O
for	O
the	O
HP-41	B-Device
.	O
</s>
<s>
Since	O
it	O
lacked	O
expandability	O
,	O
and	O
lacked	O
any	O
real	O
I/O	B-General_Concept
ability	O
,	O
both	O
key	O
features	O
of	O
the	O
HP-41	B-Device
series	O
,	O
it	O
was	O
marketed	O
as	O
an	O
HP-15C	B-Device
replacement	O
.	O
</s>
<s>
The	O
42S	O
,	O
however	O
,	O
has	O
a	O
much	O
smaller	O
form	O
factor	O
than	O
the	O
41	O
,	O
and	O
features	O
many	O
more	O
built-in	O
functions	O
,	O
such	O
as	O
a	O
matrix	B-Architecture
editor	O
,	O
complex	O
number	O
support	O
,	O
an	O
equation	B-General_Concept
solver	I-General_Concept
,	O
user-defined	O
menus	O
,	O
and	O
basic	O
graphing	O
capabilities	O
(	O
the	O
42S	O
can	O
draw	O
graphs	O
only	O
by	O
programs	O
)	O
.	O
</s>
<s>
Additionally	O
,	O
it	O
features	O
a	O
two-line	O
dot	B-General_Concept
matrix	I-General_Concept
display	O
,	O
which	O
made	O
stack	O
manipulation	O
easier	O
to	O
understand	O
.	O
</s>
<s>
As	O
this	O
calculator	O
is	O
regarded	O
amongst	O
the	O
best	O
ever	O
made	O
in	O
terms	O
of	O
quality	O
,	O
key	O
stroke	O
feel	O
,	O
ease	O
of	O
programming	O
,	O
and	O
daily	O
usability	O
for	O
engineers	O
,	O
in	O
the	O
HP	B-Device
calculator	I-Device
community	O
the	O
42S	O
has	O
become	O
famous	O
for	O
its	O
high	O
prices	O
in	O
online	O
auctions	O
,	O
up	O
to	O
several	O
times	O
its	O
introduction	O
price	O
,	O
which	O
has	O
created	O
a	O
scarcity	O
for	O
utility	O
end	O
users	O
.	O
</s>
<s>
The	O
HP-42S	B-Device
is	O
keystroke-programmable	B-Device
,	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>
The	O
HP-42S	B-Device
uses	O
a	O
superset	O
of	O
the	O
HP-41CX	B-Device
FOCAL	O
language	O
.	O
</s>
<s>
The	O
HP-42S	B-Device
supports	O
indirect	O
addressing	O
with	O
which	O
it	O
is	O
possible	O
to	O
implement	O
a	O
Universal	O
Turing	O
machine	O
and	O
therefore	O
the	O
programming	O
model	O
of	O
the	O
HP-42S	B-Device
can	O
be	O
considered	O
Turing-complete	O
.	O
</s>
<s>
No	O
memory	O
registers	B-General_Concept
are	O
used	O
.	O
</s>
<s>
In	O
May	O
2017	O
,	O
SwissMicros	O
released	O
pre-production	O
samples	O
of	O
an	O
RPN	O
calculator	O
closely	O
resembling	O
the	O
HP-42S	B-Device
,	O
the	O
DM42	O
.	O
</s>
<s>
Even	O
though	O
slightly	O
smaller	O
(	O
144×77×13mm	O
,	O
170g	O
)	O
than	O
the	O
original	O
HP-42S	B-Device
(	O
148×80×15mm	O
,	O
170g	O
)	O
,	O
the	O
calculator	O
comes	O
with	O
an	O
additional	O
top	O
row	O
of	O
keys	O
for	O
soft	O
menus	O
,	O
a	O
keyboard	O
layout	O
supporting	O
direct	O
alpha	O
character	O
input	O
,	O
a	O
much	O
larger	O
high-contrast	O
display	O
(	O
Sharp	O
low	O
power	O
transflective	O
memory	O
LCD	B-Device
with	O
a	O
resolution	O
of	O
400×240	O
,	O
protected	O
by	O
Gorilla	O
Glass	O
)	O
showing	O
all	O
four	O
stack	O
levels	O
at	O
once	O
(	O
configurable	O
)	O
,	O
ca	O
.	O
</s>
<s>
75KB	O
usable	O
RAM	B-Architecture
,	O
a	O
beeper	O
,	O
a	O
callable	O
real-time	O
clock	O
as	O
well	O
as	O
an	O
infrared	O
port	O
for	O
HP	O
82240A/HP	O
82240B	O
printer	O
support	O
and	O
a	O
USB	B-Protocol
interface	O
(	O
with	O
Micro-B	O
connector	O
)	O
emulating	O
a	O
FAT16-formatted	O
USB	B-Protocol
mass	O
storage	O
device	O
for	O
easy	O
program	O
transfer	O
and	O
state	O
backup/	O
transfer	O
as	O
well	O
as	O
for	O
firmware	O
updates	O
.	O
</s>
<s>
The	O
calculator	O
,	O
which	O
comes	O
in	O
a	O
stainless	O
steel	O
case	O
with	O
matte	O
black	O
physical	O
vapor	O
deposition	O
(	O
PVD	O
)	O
coating	O
,	O
supports	O
keyboard	O
overlays	O
and	O
is	O
based	O
on	O
a	O
modified	O
version	O
of	O
Thomas	O
Okken	O
's	O
GPLed	O
Free42	B-Device
simulator	O
with	O
Intel	O
's	O
decimal	B-Application
floating-point	O
math	O
library	O
for	O
higher	O
precision	O
(	O
decimal128	O
)	O
running	O
on	O
an	O
STM32L476RG	O
processor	O
(	O
ARM	B-Architecture
Cortex-M4	O
core	O
,	O
128KB	O
RAM	B-Architecture
,	O
1MB	O
internal	O
flash	O
)	O
with	O
another	O
8MB	O
of	O
external	O
QSPI	O
flash	O
(	O
of	O
which	O
ca	O
.	O
</s>
<s>
It	O
is	O
powered	O
by	O
a	O
CR2032	B-Algorithm
coin	B-Algorithm
cell	I-Algorithm
or	O
via	O
USB	B-Protocol
and	O
clocked	O
dynamically	O
at	O
24-80MHz	O
.	O
</s>
<s>
An	O
open-source	O
software	O
version	O
of	O
the	O
HP-42S	B-Device
(	O
Free42	B-Device
)	O
was	O
developed	O
by	O
Thomas	O
Okken	O
that	O
runs	O
on	O
iOS	O
,	O
Android	O
,	O
Windows	O
,	O
MacOS	O
,	O
and	O
Linux	O
.	O
</s>
<s>
Its	O
source	O
code	O
has	O
been	O
released	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
