HP 20B manual Keys Display Description RPN Stack

Mathematical Calculations

Table 2-3Simple Arithmetic Calculations in RPN Mode

Keys Display Description RPN Stack

*

Finishes the operation and

displays the results.

Pressing Ior =when you are not entering a number duplicates the number on Level 1. That is, the number on Level 1 is pushed on the stack, making Levels 1 and 2 equal. In the example above, pressing Iafter *duplicates 77 on the stack, making Levels 1 and 2 equal. See Figure 5.

Previous Value

Previous Value

77

77

Figure 5 Duplicating a Number on the Stack

In RPN, the parentheses keys ()manipulate the stack. Pressing (performs a roll down of the stack. A roll down causes the stack to roll towards the bottom of the stack, during which the number in Level 2 moves down to Level 1, the number in Level 3 moves down to Level 2, the number in Level 4 moves down to Level 3, and the number in Level 1 moves up to Level 4. The (key has a small down arrow on it as a reminder of the roll down feature. With the numbers entered into the stack shown in the left column in Figure 6, pressing (performs the roll down of the stack shown in the right column.

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