HP HP-28S - Keying in Numbers

Keying In Numbers
You can enter numbers as a mantissa and an exponent, where the
value of the number is the product of the mantissa and 10 raised to
the power of the exponent. The mantissa or the exponent or both can
be negative.
For example,
key in the number -4.2 x 10-12.
First key in the digits for the mantissa.
4.2 .-::2,-:----------;1-=9
1: .666666666667
4.20
liEtloaEHIl1:Hemm.
If you make a mistake, press [!j to erase the mistake and then key in
the correct digits.
Next
make the mantissa negative.
ICHSI
2: 19
1: .666666666667
-4.20
liEtloaEHIl1:Hemm.
"CHS" stands for "change sign"-pressing I CHS I a second time would
make the mantissa positive again.
Now begin the exponent.
I EEX I 2: 19
1: .666666666667
-4.2EO
liEtloaEHIl1:Hemm.
"EEX" stands for "enter exponent." The E in the command line marks
the number's exponent. If you press I EEX I by mistake for a number
without an exponent, you can erase the E by pressing [!j, just as you
would erase an incorrect digit.
Key in
the digits for the exponent.
12
2: 19
1: .666666666667
-4.2E120
liEtloaEHIl1:Hemm.
2: Doing Arithmetic 39