Section 10: Programming with ALPHA Strings154
Now run the LOG1 program to find the log of 12. Notice how the program first prompts you for the number, then labels the output.
Keystrokes Display    
  Takes the HP-41C out of PRGM mode. Number remains from previous example.
  XEQ _ _    
  The prompt for the number.
  12 _    
  The number.
  The data label and the data.
g CLX 
Data labeling can also be accomplished by recalling (using ARCL ) the ALPHA string from a register, and the result from the X-register (also using ARCL ).
Program Status
To detect the status of your executing program, you can place ALPHA strings in strategic places in your programs. When the string is displayed momentarily, you know exactly how far execution has progressed.
Prompting for ALPHA Strings
You can prompt for the input of ALPHA information just like you would for numbers. Using the AON (ALPHA on) and AOFF (ALPHA off) functions, you can even control the mode the calculator is set to when the program stops for input.
AON places the HP-41C into ALPHA mode and AOFF takes the calculator out of ALPHA mode.
Clearing the Display
To clear the contents of the display at any time during a running program, simply key in CLD (clear display) as a line in the program. This clears the display and then displays the X-register, or the ALPHA register (if the calculator is in ALPHA mode).
Using ASHF (ALPHA Shift)
ASHF is a handy HP-41C function that shifts the contents of the ALPHA register to the left by six characters. Manually or in program, when you wish to store a long ALPHA string into several storage registers, ASHF makes the task simple. (Remember, each data storage register can hold up to six ALPHA characters.) When ASHF is executed, the left-most six characters in the ALPHA register are shifted off to the left and are lost. The remaining characters in the ALPHA register all shift to the left by six positions.