The Key In Rpn Mode - HP 12C Platinum User Manual

90 Section 5: Additional Operating Features
Errors. If you attempt an improper operation — such as division by zero — the
calculator will display the word Error followed by a digit (0 through 9). To clear
the Error display, press any key. This does not execute that key's function, but
does restore the calculator to its condition before the improper operation was
attempted. Refer to Appendix D for a list of error conditions.
Pr Error. If power to the calculator is interrupted, the calculator will display Pr
Error when next turned on. This indicates that Continuous Memory — which
contains all data, program, and status information — has been reset.
The Key in RPN Mode
Suppose you need to subtract $25.83 from $144.25, and you (mistakenly) key in
25.83 as the first number and then key in 144.25 as the second number. But then
you realize that when written down on paper, the desired calculation reads
144.25 – 25.83, so that you have unfortunately keyed in the second number first.
To correct this mistake, merely exchange the first and second numbers by pressing
~, the exchange key.
Keystrokes
(RPN mode)
25.83\144.25
~
-
The ~ key is also useful for checking the first number entered to make sure you
keyed it in correctly. Before pressing the operation key or equals key, however,
you should press ~ again to return the second number entered to the display.
Regardless of how many times you press ~, the calculator considers the number
in the display to be the second number entered.
The Key in RPN Mode
Occasionally you may want to recall to the display the number that was there
before an operation was performed. (This is useful for doing arithmetic calculations
with constants and for recovering from errors in keying in numbers.) To do so,
press gF (LAST X). This section describes how to use gF in RPN mode.
Display
Oops! You mistakenly keyed in the
144.25
second number first.
Exchanges the first and second
25.83
numbers. The first number keyed in
is now in the display.
The answer is obtained by pressing
118.42
the operation key.