Section 2: Controlling The Display; Display Control Keys - HP 25 Owner's Handbook Manual

Section 2
Controlling the Display
In the HP-25 , numbers in the display normally appear rounded
to only two decimal places. For example , the fixed constant
7T,
which is actually in the calculator as 3.141592654, normally
appears 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 computes 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 an swer to only
two decimal places :
Press Display
2
mm
3
0 c. . . : c 1
6
"-" .o-'- o_---'
However , inside the calculator all numbers 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 answer that is actually carried to 10 digits :
I
6.000000000 x10
oo
l
---~
You see only
t
t
these d .... , i_g_it_s_ . _ . _ . _ _ -----'
Display Control Keys
. .. but these digits
are also, present.
~
allow s numbers to be displayed in fixed decimal point for-
mat ,
ISCI
I
displays numbers in scientific notation format, and
IENG 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 m anner in which numbers are
displayed in the HP-25 . The actual number itself is not altered
by any of the display control key s. No matter 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) .
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