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Appendix B: Algebraic Mode (ALG) 239
File name: hp 12c pt_user's guide_English_HDPMF123E27 Page: 239 of 275
Printed Date: 2005/8/1 Dimension: 14.8 cm x 21 cm
Keystrokes
(ALG mode)
Display
OO
0.00
Clears any pending operations.
456
-
75
z
381.00
18.5
§
20.59
68
z
1,400.43
1.9
}
737.07
The Key in ALG Mode
LAST X in ALG mode is not used in this book. It is the one function that is quite
different in ALG and RPN modes. Refer to page 234 for the list of 23 different key
presses that cause the displayed X-register to be copied into the LAST X register in
RPN mode. In ALG mode, those key presses do
not
cause a refresh of the LAST X
register. Instead, the displayed number is copied into the LAST X register when a
new
calculation commences either with
digit entry
(i.e., when one of the digits
0-9, the decimal point, or
Æ
is pressed) or with
gF
itself, but not when a
number is recalled using
:
.
When
gF
is actually
executed
in ALG mode, it simply swaps the value in the
X-register with the value in LAST X. Therefore, in ALG mode, it never lifts the stack
and in general, it changes the value in LAST X. However, in RPN mode,
gF
always lifts the stack and leaves the value in LAST X unchanged.
In general, LAST X in ALG mode is only useful in programs, where it can often be
used instead of a numbered storage register, as it persists unchanged at least until
digit entry or
gF
. There is an example of its use in the Combinations program
in the hp 12c platinum Solutions Handbook.
The History Stack in ALG Mode
In ALG mode, the stack holds a “history” of 4 completed results. These results may
be rearranged using
d
and
~
in the same way as described on page 230, for
RPN mode.
Note that once a two-numbered function (such as
+
,
-
,
§
,
z
or
q
) has had
the second argument entered, the two arguments cannot then be swapped using
~
because when the second argument is entered it replaces the first, which is
removed from the stack. So, if you wish to do 25.83
-
144.25, but then realize
you meant to do 144.25
-
25.83, the way to correct this is to proceed and do
}Þ
. All
~
will do at this point is replace the 144.25 with whatever was
displayed before the 25.83 was entered, and the first argument remains
unchanged.