Section 3: Automatic Memory Stack and ALPHA Register54
 Example. A bacteriologist tests a certain strain whose population typically increases by 15% each day (a growth factor of 1.15). If he starts a sample culture of 1000, what will be the bacteria population at the end of each day for five consecutive days? Method: Put the growth factor (1.15) in the Y-, Z-, and T-registers and put the original population (1000) in the X-register. Thereafter, you get the new daily population whenever you press  × .

 Keystrokes Display 1.15 1.15 _ Growth factor. ENTER 1.15000 ENTER 1.15000 ENTER 1.15000 Growth factor is now in T. 1000 1000 _ Starting population. × 1,150.0000 Population after 1st day. × 1,322.5000 Population after 2th day. × 1,520.8750 Population after 3th day. × 1,749.0063 Population after 4th day. × 2,011.3572 Population after 5th day.
When you press  ×  the first time, you calculate 1.15 × 1000. The result (1,150) is displayed in the X-register and a new copy of the growth factor drops into the Y-register. Since a new copy of the growth factor is duplicated from the T-register each time the stack drops, you never have to reenter it.
Notice that performing a two-number operation such as  ×  causes the number in the T-register to be duplicated there each time the stack is dropped. However, the R  function simply rotates the contents of the stack registers; it does not rewrite any number, but merely shifts the numbers that are already in the stack.