<s>
The	O
HP-27	B-Device
was	O
a	O
hand-held	O
scientific	O
and	O
financial	O
,	O
but	O
not	O
programmable	O
,	O
calculator	O
made	O
by	O
Hewlett-Packard	O
between	O
1976	O
and	O
1978	O
.	O
</s>
<s>
Unlike	O
all	O
previous	O
HP	O
's	O
pocket	O
calculators	O
,	O
the	O
HP-27	B-Device
could	O
do	O
mathematic	O
,	O
statistic	O
and	O
business	O
operations	O
.	O
</s>
<s>
It	O
used	O
Reverse	O
Polish	O
Notation	O
(	O
RPN	O
)	O
for	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-27	B-Device
also	O
had	O
a	O
10-digit	O
red	O
LED	O
display	O
and	O
10	O
registers	O
to	O
store	O
numbers	O
.	O
</s>
