Keystrokes Display    
USER   0.0000   Puts the calculator in USER mode and turns on the USER annunciator.
38 HEATΣ+ )  535.80000   Since HEAT is assigned to the Σ+ key in USER mode, you can run HEAT quickly and simply as a keyboard function.
Try holding the HEATΣ+ ) key down briefly. Notice how the HP-41C reminds you that HEAT is assigned to that key (in USER mode) by showing the name HEAT in the display while you press and hold the key. (Holding the key down longer than about a half second nullifys the function.)
Keystrokes Display    
  Press and hold the key for a moment to see the program name. When you release the key, the function is executed, giving the answer in Btu per hour.
45 HEAT  634.50000   Btu per hour.
g CLX   0.0000   Clears the display.
USER   0.0000   Takes the HP-41C out of USER mode.
Programming the HP-41C is that easy! The exciting capabilities of the HP-41C together with the ease of programming and execution make the HP-41C possibly the most usable, capable handheld calculator system you can own.
The HP-41C Configuration
Continuous Memory. The HP-41C maintains all information in the calculator in Continuous Memory—one of the newest, most advanced memory systems available in a scientific calculator. All data, programs and functions—everything in the calculator—are maintained by Continuous Memory while the calculator is turned off. You can turn the HP-41C off, then back on and continue working where you left off. In fact, to conserve battery power, the HP-41C turns itself off after 10 minutes of inactivity.
Alphabetic/Numeric Capability. The HP-41C is one of the first handheld scientific calculators to offer both alphabetic and numeric character capability. Alphabetic characters allow you to name and label programs and functions, prompt for data with meaningful words or sentences, display exacting error messages, label variables and constants—even display messages!