


Automatic Memory Stack and ALPHA Register


This section covers the detailed operation of the automatic memory stack
and the ALPHA register. If you wish to learn how the stack and ALPHA register
work, and how you can take advantage of some of the more powerful features of
the HP41C, we suggest that you work through this section. Otherwise, you
may wish to skip this section for now and continue with
section 4, Using
HP41C functions.


The Automatic Memory Stack


Automatic storage of intermediate results is the reason that HP41C makes
solution of even the most complex equations simple. The automatic storage is
made possible by the HewlettPackard memory ‘‘stack.’’


Here is what the registers of the automatic memory stack look like:


The

T

0.0000

Automatic

Z

0.0000

Memory Stack

Y

0.0000


X

0.0000



When you are in normal mode, that is not in PRGM, USER, or ALPHA mode,
numbers that appear in the display are the same as the contents of the
Xregister in the calculator.


Each register in the stack holds a 10digit number and its 2digit
exponent of 10. ALPHA characters and their relationship to the stack are
covered later. For now, let’s work with just numbers.


Basically, numbers are stored and manipulated in the HP41C
‘‘registers.’’ Each number, no matter how few digits
(e.g., 0, 1 ,5) or many (e.g., 3.14159265, –15.78352, or
1.7588028 × 10^{11}), occupies one entire register. We label
these registers X, Y, Z, and T. They are ‘‘stacked,’’
like shelves, one on top of the other, with the Xregister on the bottom and
the Tregister on top.


The contents of these registers, as well as all other information in the
HP41C, are maintained by the calculator’s Continuous Memory. Even when
the HP41C is turned off, the values stored in the stack registers are all
‘‘remembered’’ by the calculator.


When you execute a function, the result is always placed in the Xregister (the
display). So when you compute the reciprocal of 5...


