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Section 3
The Automatic Memory Stack
The Stack
Automatic storage of intermediate results is the reason that the
HP-25 slides so easily through the most complex equations.
And automatic storage is made possible by the Hewlett-Packard
automatic memory stack.
Initial Display
When you first switch the calculator ON, the display shows
. This represents the contents of the display, or X-
register.
Basically, numbers are stored and manipulated in the machine
"registers."" Each number, no matter how few digits (e.g., 0, 1,
or 5) or how many (e.g., 3.141592654, —23.28362, or 2.87148907
X 10%7), occupies one entire register.
The displayed X-register, which is the only visible register, is
one of four registers inside the calculator that are positioned to
form the automatic memory stack. We label these registers X,
Y, Z, and T. They are ''stacked'' one on top of the other with
the displayed X-register on the bottom. When the calculator is
switched ON, these four registers are cleared to 0.00.
Name
Register
T
0.00
Z
0.00
Y
0.00
X
0.00
Always displayed.
Manipulating Stack Contents
The B (roll down) and BER(x exchange y) keys allow you to
review th; stack contents or to shift data within the stack for
computation at any time.
35
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