Section 4: Using HP-41C Functions59
Function Editing and Correction
On the HP-41C, you can edit function names before you execute, or even terminate completely, using   . For example:
Keystrokes Display    
XEQ   XEQ _ _   Terminate XEQ by pressing   .
     720.000000   The function is terminated and the value in X displayed.
XEQ   XEQ _ _   Begin again.
ALPHA ENT  XEQ ENT _   Use    to edit the function name.
     XEQ EN _   Characters are deleted one at a time.
G  XEQ ENG _   The corrected function name.
           XEQ _   You are back to the XEQ function.
     720.000000   Pressing    again terminates XEQ and returns the HP-41C to normal mode.
g FIX 4  720.0000   Return to FIX 4.
g CLX   0.0000   Clear the displayed X-register.
If you attempt to execute a function (using XEQ ) whose name does not exist in the calculator, the HP-41C will display NONEXISTENT. For example, if you attempt to execute SINE, the calculator will display NONEXISTENT. In the HP-41C, the sine function is spelled SIN.
Functions that require numeric data can not operate ALPHA characters. If a function requiring numeric data attempts to execute using ALPHA characters, the HP-41C displays ALPHA DATA. A complete listing of all HP-41C error messages and their meaning is given in appendix E.
The HP-41C Catalogs
The HP-41C has three catalogs of functions. One catalog contains all functions and programs that you have written and stored in program memory. Another catalog contains all functions that become active when you plug in extensions to the HP-41C like application modules or other accessories. And the third catalog contains all of the standard HP-41C functions (this catalog contains the bulk of functions you will be using).