Section 3: Automatic Memory Stack and ALPHA Register52
###### Order of Execution
When you see a problem like this one:
{ 37 × [ (5 ÷ 18) + (5 ×.13) ] } ÷ 3.87
you must decide where to begin before you ever press a key.
Experienced HP calculator users have learned that by starting every problem at its innermost set of parentheses and working outward, just as you would with paper and pencil, you maximize the efficiency and power of your HP calculator. Of course, with the HP-41C you have tremendous versatility in the order of execution.
For example, you could solve some problems by working through them in left-to-right order, but not all problems can be solved correctly this way. The best way to work any problem is to begin with the innermost parentheses and work outward. So, to solve the problem above:
 Keystrokes Display 5 ENTER 5.0000 18  ÷ 0.2778 Result of (5 ÷ 18). 5 ENTER 5.0000 .13  × 0.6500 Result of (5 × .13). + 0.9278 Result of [(5 ÷ 18) + (5 × .13)]. 37  × 34.3278 Result of 37 × [(5 ÷ 18) + (5 × .13)]. 3.87  ÷ 8.8702 Result of {37 × [(5 ÷ 18) + (5 × .13)]} ÷ 3.87.
###### Last X
In addition to the four stack registers that automatically store intermediate results, the HP-41C also contains a separate automatic register, the LAST X register. This register preserves the value that was last in the display before the execution of a function. To place the contents of the LAST X register into the displayed X-register again, press g LASTX.
Recovering From Mistakes
LASTX makes it easy to recover from keystroke mistakes, such as executing the wrong function or keying in the wrong number. For example, divide 287 by 13.9 after you have mistakenly divided by 12.9.