HP 12C Platinum Instruction Manual page 2

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HP 12C Platinum Using the RPN stack to solve problems efficiently
The benefits of understanding RPN stack operations
RPN stands for Reverse Polish Notation and is one of two operating modes available on the HP12C Platinum. Mastering
RPN leads to an enhanced performance when using the calculator. The first step to master RPN usage is to know all of
its available resources.
Understanding the HP12C Platinum operation
When in normal, 'run' mode, every operation performed in the HP12C Platinum uses the display contents or places
results on it. The display always shows the contents of the X-register. A register is a predefined place in the calculator
memory that is able to hold a formatted number with a ten-digit mantissa and a two-digit exponent of ten. The X-register
is one of five registers that form the RPN stack, represented in Figure 1 with all contents cleared to zero.
Anytime a number is keyed in, the X-register is updated to hold this number. It is then available for use.
Example 1: What is the most common keystroke sequence to compute the reciprocal of 7.2? What registers in the
stack are used?
Solution: The most common keystroke sequence to compute the reciprocal of 7.2 is:
7.2 y
In this case, simply typing in the number and pressing the related key are enough to compute the resulting
value. There are other functions that use only the X-register contents, like g¿ or gr. These are
the 'one-number functions', and when they are pressed, the calculator proceeds with the following
operation sequence:
1. take a copy of the X-register contents and put it in L-register (last-x);
2. replace actual X-register contents with the resulting value.
If a second number needs to be typed in right after the first one to be used with it, they must be separated
with the \ key. For example, to add 3 and 5 together, you would press 3\5+.
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Stack registers
T
Z
Y
X
L
Figure 1
(normally shown in the display)
- 2 - HP 12C Platinum Using the RPN stack to solve problems efficiently - Version 1.0
Figure 2