different levels are referred to as the stack levels, i.e., stack level 1, stack level 2, etc.

Basically, what RPN means is that, instead of writing an operation such as 3 + 2, in the calculator by using

3+2`

we write first the operands, in the proper order, and then the operator, i.e.,

3`2`+

As you enter the operands, they occupy different stack levels. Entering 3`puts the number 3 in stack level 1. Next, entering 2`pushes the 3 upwards to occupy stack level 2. Finally, by pressing +, we are telling the calculator to apply the operator, or program, + to the objects occupying levels 1 and 2. The result, 5, is then placed in level 1.

Let's try some other simple operations before trying the more complicated expression used earlier for the algebraic operating mode:

123/32123`32/

424`2Q3√2727`R3@»

Notice the position of the y and the x in the last two operations. The base in the exponential operation is y (stack level 2) while the exponent is x (stack level 1) before the key Q is pressed. Similarly, in the cubic root operation, y (stack level 2) is the quantity under the root sign, and x (stack level 1) is the root.

Try the following exercise involving 3 factors: (5 + 3) ⋅ 2

5`3`+

Calculates (5 +3) first.

2X

Completes the calculation.

Let's try now the expression proposed earlier:

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