Section 3: Automatic Memory Stack and ALPHA Register49
The simple old-fashioned math notation helps explain how to use your calculator. Both numbers are always positioned in the calculator in the natural order first, then the operation is executed. There are no exceptions to this rule. Subtraction, multiplication, and division work the same way. In each case, both numbers must be in the proper position before the operation can be performed.
###### Chain Calculations
You’ve already learned how to key numbers into the calculator and perform calculations with them. In each case you first needed to position the numbers in the stack manually using the ENTER  key. However, the stack also performs many movements automatically. These automatic movements add to its computing efficiency and ease of use, and it is these movements that automatically store intermediate results. The stack automatically ‘‘lifts’’ every calculated number in the stack when a new number is keyed in because it knows that after it completes a calculation, any new digits you key in are part of a new number. Also, the stack automatically ‘‘drops’’ numbers into position when you perform two-number operations.
To see how it works let’s solve 21 + 38 + 19 + 53 = ?
For purposes of simplification, this example shows the stack cleared to zeros.
 Keystrokes Stack Contents g CLX 0.0000
 21 T 0.0000 21 is keyed in. Z 0.0000 Y 0.0000 (Displayed) X 21 _ ENTER T 0.0000 21 is copied into Y. Z 0.0000 Y 21.0000 (Displayed) X 21.0000 38 T 0.0000 38 is keyed in. Z 0.0000 Y 21.0000 (Displayed) X 38 _ + T 0.0000 38 and 21 are added together. Z 0.0000 The answer, 59, is in X and the Y 0.0000 display. (Displayed) X 59.0000 19 T 0.0000 19 is keyed in and the 59 is Z 0.0000 automatically raised into Y. Y 59.0000 (Displayed) X 19 _