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Mathematical Calculations

When an operation is performed on the stack, addition (+)for instance, the calculator "pops" or moves the two numbers

from the bottom levels (Levels 1 and 2) out of the stack, performs the operation, and "pushes" the results back into the stack.

With the numbers entered into the stack as shown in Figure 3, pressing + changes the stack as shown in Figure 4. Note

that when the numbers are "popped" out to add 23 and 41, Level 4 of the stack remains unchanged.

-15

Figure 4 The RPN Stack of Figure 3 after the Addition Operation

Last Number

Each time you perform a mathematical operation, the content of Level 1 of the stack is saved. Pressing :d recalls that

number. This functionality can be used to undo an erroneous key press, or if you want to reuse a number, such as 56.123 in

the expression:





 

123.56

123.5623.1



See Table 2-2 for an example using the

last number

function.

Table 2-2 Last Number

Keys Display Description

:u3I

Sets

FIX=

to 3.000

<<<<<

Selects

RPN

as the operating mode.

O1c23

I56c1

Inputs 1.23 and 56.123

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 74 75

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Hp 20B User Manual Page 19