Running the program. Press the following keys to run the ‘‘HEAT’’ program. Find the heat loss of the water heater at temperature differences of 22 and 65 degrees Fahrenheit.
Keystrokes Display    
PRGM  211.5000   Takes the calculator out of PRGM mode—turns PRGM annunciator off. Results remains from previous example.
22  22 _   The first temperature difference.
XEQ (execute)  XEQ _ _   Prompts Execute what? with XEQ _ _.
ALPHA HEAT ALPHA   310.2000   Press the letter keys to spell the program name. The program is executed and the heat loss (Btu per hour) is displayed.
65  65 _   The second temperature difference.
XEQ   XEQ _ _   Execute what?
ALPHA HEAT ALPHA   916.5000   Btu per hour.
g CLX   0.0000   Clear the display.
You can save even more time and keystrokes by assigning the program to a key on the keyboard! Programs that you assign to keys are treated just like any other functions when you place the HP-41C into a special ‘‘USER’’ mode. Then you can execute your program with a single press of the key—without entering the program name each time! Let’s assign the HEAT program to the Σ+ key now.
Keystrokes Display    
g ASN   ASN _   The HP-41C prompts Assign what?
ALPHA HEAT ALPHA   ASN HEAT _   The program name. The HP-41C is now prompting you for the key location.
Σ+   0.0000   HEAT is now assigned to the Σ+ location.
Now run the HEAT for temperature differences of 38°F, 27°F and 45°F. To run HEAT, you now press the USER key, located just below the display, to place the HP-41C into USER mode. Notice that the HP-41C lets you know that it is in USER mode by turning on the USER annunciator in the display.