HP 20B manual Last Number, U3I, O1c23 I56c1

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

-15

12

64

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 :drecalls 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:

1.23  56.123

56.123

See Table 2-2 for an example using the last number function.

Table 2-2Last Number

Keys Display Description

:u3I

Sets FIX= to 3.000

<<<<<

II

Selects RPN as the operating mode.

O1c23

I56c1

23

Inputs 1.23 and 56.123

19