<s>
The	O
HP-25	B-Device
was	O
a	O
hand-held	O
programmable	B-Application
scientific/engineering	O
calculator	O
made	O
by	O
Hewlett-Packard	O
between	O
early	O
January	O
1975	O
and	O
1978	O
.	O
</s>
<s>
The	O
HP-25	B-Device
was	O
introduced	O
as	O
a	O
cheaper	O
(	O
US$195	O
MSRP	O
)	O
alternative	O
to	O
the	O
ground-breaking	O
HP-65	B-Device
.	O
</s>
<s>
To	O
reduce	O
cost	O
,	O
the	O
HP-25	B-Device
omitted	O
the	O
HP-65	B-Device
'	O
s	O
magnetic	O
card	O
reader	O
,	O
so	O
it	O
could	O
only	O
be	O
programmed	O
using	O
the	O
keyboard	O
.	O
</s>
<s>
The	O
model	O
HP-25C	B-Device
,	O
introduced	O
in	O
1976	O
,	O
addressed	O
that	O
shortcoming	O
through	O
the	O
first	O
use	O
of	O
battery-backed	O
CMOS	B-Device
memory	I-Device
in	O
a	O
calculator	O
,	O
termed	O
continuous	B-Device
memory	I-Device
by	O
HP	O
.	O
</s>
<s>
Like	O
all	O
early	O
HP	B-Device
calculators	I-Device
,	O
the	O
25	O
used	O
the	O
Reverse	O
Polish	O
Notation	O
(	O
RPN	O
)	O
for	O
entering	O
calculations	O
,	O
working	O
on	O
a	O
four-level	O
stack	B-Application
(	O
x	O
,	O
y	O
,	O
z	O
,	O
t	O
)	O
.	O
</s>
<s>
The	O
HP-25	B-Device
used	O
a	O
10-digit	O
red	O
LED	O
display	O
and	O
was	O
the	O
first	O
calculator	O
to	O
introduce	O
the	O
"	O
engineering	O
"	O
display	O
option	O
,	O
a	O
denormalized	O
mantissa/exponent	O
format	O
where	O
the	O
exponent	O
is	O
always	O
a	O
multiple	O
of	O
3	O
to	O
match	O
the	O
common	O
SI	O
prefixes	O
,	O
e.g.	O
</s>
<s>
The	O
HP-25	B-Device
had	O
memory	O
space	O
for	O
up	O
to	O
49	O
program	O
steps	O
.	O
</s>
<s>
It	O
was	O
the	O
first	O
HP	B-Device
calculator	I-Device
which	O
used	O
fully	O
merged	O
keycodes	O
(	O
storing	O
prefix	O
key	O
and	O
function	O
key	O
together	O
in	O
one	O
program	O
location	O
)	O
to	O
save	O
memory	O
space	O
.	O
</s>
<s>
The	O
HP-25	B-Device
was	O
about	O
25%	O
smaller	O
than	O
the	O
HP-65	B-Device
.	O
</s>
<s>
It	O
used	O
the	O
same	O
trapezoid	O
profiled	O
keys	O
introduced	O
with	O
the	O
HP-65	B-Device
.	O
</s>
<s>
The	O
HP-25	B-Device
was	O
regarded	O
as	O
a	O
competitor	O
to	O
the	O
TI-58	B-Device
and	O
TI-58C	B-Device
calculators	O
offered	O
by	O
Texas	O
Instruments	O
.	O
</s>
<s>
Looking	O
strictly	O
at	O
the	O
functionality	O
and	O
capacity	O
,	O
the	O
more	O
equal	O
competitor	O
would	O
be	O
the	O
TI-57	B-Device
.	O
</s>
<s>
It	O
lacked	O
a	O
few	O
of	O
the	O
HP-25	B-Device
'	O
s	O
functions	O
,	O
but	O
had	O
some	O
other	O
advantages	O
.	O
</s>
<s>
One	O
notable	O
deficiency	O
of	O
the	O
HP-25/25C	O
was	O
the	O
lack	O
of	O
a	O
subroutine	O
capability	O
,	O
at	O
a	O
time	O
when	O
the	O
TI-58	B-Device
and	O
even	O
the	O
earlier	O
SR-56	O
had	O
subroutines	O
.	O
</s>
<s>
Although	O
49	O
fully	O
merged	O
keycodes	O
were	O
roughly	O
equivalent	O
to	O
the	O
unmerged	O
100	O
steps	O
of	O
the	O
SR-56	O
;	O
by	O
the	O
time	O
the	O
TI-58	B-Device
arrived	O
with	O
480	O
steps	O
,	O
subroutines	O
,	O
DSZ	O
loops	O
,	O
etc.	O
,	O
the	O
HP-25/25C	O
had	O
serious	O
competition	O
.	O
</s>
<s>
And	O
TI	O
would	O
introduce	O
a	O
TI-58C	B-Device
with	O
continuous	B-Device
memory	I-Device
.	O
</s>
