Section 2
Controlling the Display
In
the HP-25, numbers
in
the display normally
appe
ar rounded
to only
two
decimal places.
For
example, the fixed
const
ant
7T,
which
is
ac
tually
in
the
ca
lculator as 3.141592654, normally
app
ears in the display as
~
(unless you tell the
calculator
to show you the
number
rounded to a greater
or
lesser
number
of
decimal places).
Although a
number
is
normally shown to only two decimal
places, the HP-25 always
compute
s internally using
each
num-
ber as a 10-digit mantissa and a two-digit
exponent
of
10
.
For
example,
when
you
compute
2 x 3, you see the ans
wer
to only
two decimal places:
Press Display
2 mm 3 0
c...:c1
6
"-"
.o
-'-
o
_---'
However
, inside the calculator all
number
s have
10
digit man-
tissas and two-digit exponents
of
I O. So the calculator actually
calculates using full 10-digit numbers:
2.000000000 x
10
00
mm 3.000000000 x
10
00
0
yields an a
nswer
that
is
actually carried to
10
digits:
I 6.00
0000000
x10
oo
l
---~
You
see only t t
these d
....
,
i_g_it_s_
. _. _.
__
-----'
Display Control Keys
.
..
but these digits
are also, present.
~
allows numbers to be displayed
in
fixed decimal point for-
mat,
ISCI I displays numbers
in
scientific notation format, and
I
ENG
I displays numbers
in
engineering notation, with
exponents
of
10
shown
in
mUltiples
of
three (e.g. ,
10
3
,
10
-
6
,
10
9
) .
Display control alters only the ma
nner
in
which numbers are
displayed
in
the HP-25.
The
actual
number
itself
is
not altered
by any
of
the display control keys.
No
ma
tter
what notation you
select, these rounding options affect the display
only-the
HP-25 always calculates internally with a full 10-digit
number
(multiplied by
10
raised to a two-digit exponent).
25
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