HP HP-25 - Page 36

To key in negative exponents of 10, key in the number, press
= . pressH to make the exponent negative, then key in the
power of 10. For example, key in Planck’s constant (h)—
roughly, 6.625 x 107%" erg sec.—and multiply it by 50.
Press Display
Ea[Fx]2
6.625 B
6.625 -00
27 6.625 -27
50 Erg sec.
Using the @@ key, you can key in numbers made up of 10-digit
mantissas and two-digit exponents of 10. However, when you
use the [E34 key, the HP-25 displays each number as an eight-
digit mantissa and a two-digit exponent of 10. In a few cases, a
number may have to be altered slightly in form before you can
key it in using the EZq key:
= If youkey in a number whose mantissa contains more than
eight digits to the left of the decimal point, the [Z34 key is
overridden and does not operate. Begin again and key in
the number in a form that displays the mantissa with eight
digits or less to the left of the decimal point before pressing
the B3 key. (Thus, 123456789.1 x 10?3 could be keyed in
as 12345678.91 x 10%.)
= If you key in a number whose first significant digit occurs
after the first eight digits of the display, the [E24 key does
not operate upon that number. To key in the number cor-
rectly, begin again and place the number in a form such that
its first significant digit is one of the first eight digits of the
display, then proceed using the[E23 key. (Thus, 0000.000025
X 10% cannot be keyed in in that form. It could be keyed in
as 0000.00025 x 107, or as 0.000025 x 10%, for example.)