The result, 3.00, is calculated and displayed immediately.

There are four special registers used for storing numbers during calcula- tions, which are stacked on top of one another. Called “the stack,” these registers are designated X,Y, Z, and T. X is on the bottom, and T is on the top. Unless the calculator is in Program mode, the number in the display is the number in the X-register. Primarily, the numbers in the X- and Y-registers are the numbers used in calculations. The Z and T registers are used for the automatic retention of intermediate results during chain calculations.

The Rkey separates numbers in the vertical stack and positions them in the X- and Y-registers, and, in addition to displaying intermediate results, this vertical arrangement of the stack allows you to copy and rearrange numbers without reentering them. For more complex problems requiring two or more operations, you do not need to enter parentheses to set operational priority. Key in numbers and operations inside the parentheses first, followed by those outside of the parentheses. If a problem has more than one set of parentheses, start by working with the operations and numbers in the innermost parentheses and work out.

For example, in RPN mode calculate (3 + 4)(5 + 6). See

Table 1-2.Although this is a simple example, you can use the principles introduced here when working with more complex problems.

8 Getting Started