Notice that the display shows several levels of output labeled, from bottom to
top, as 1, 2, 3, etc. This is referred to as the stack of the calculator. The
different levels are referred to as the stack levels, i.e., stack level 1, stack level
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.
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. A simpler
way to calculate this operation is by using: 3`2+.
Let's try some other simple operations before trying the more complicated
expression used earlier for the algebraic operating mode:
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
Try the following exercise involving 3 factors: (5 + 3) × 2
Let's try now the expression proposed earlier:
Calculates (5 +3) first.
Completes the calculation.