Section 3: Automatic Memory Stack and ALPHA Register48
Here is what happens when you executed the   function:
First, after you keyed in the numbers, the stack looked like this (the T- and Z-registers are shown cleared to zero for clarity):
 T 0.0000 Z 0.0000 Y 27.9300 X 167.54 _ (Displayed)
Then when you pressed   , the result, the square root of the number in the X-register, was placed in the X-register (displayed).
 T 0 Z 0 Y 27.93 X 112.944 (Displayed)
The one-number function executes upon only the number in the displayed X-register, and the answer writes over the number that was in the X-register. No other stack register is affected by a one-number function.
###### Two-Number Functions and the Stack
The HP-41C performs arithmetic operations by positioning the numbers in the stack the same way you would on paper. For instance, if you wanted to add 17 and 46 you would write 17 on the paper and then write 46 underneath is, like this:
 17 + 46
and then you would add, like this:
 17 + 46 63
Numbers are positioned the same way in the calculator. Here’s how it is done.
 Keystrokes Display g CLX 0.0000 Clears the displayed X-register. 17 17 _ 17 is keyed into the X-register. ENTER 17.0000 17 is copied from X into Y. 46 46 _ 46 writes over the 17 in the display. + 63.0000 The result is in X and the display.