Section 12: Subroutines189
  Σ–   yx   x2   10x   ex  
  Σ+   1/x   √x   LOG   LN  
  A   B   C   D   E  
    When you press Σ+ in USER mode, the HP-41C first searches for LBL A within the current program.    
If there is no LBL A in the current program, the calculator executes the Σ+ function. Remember, the calculator searches only the current program for the local label, it does not search all of program memory.
If there is a LBL A in the current program, execution begins at that point. Using local labels requires the calculator to be set to the portion of program memory containing the local label prior to running the program.
When you reassign any other function to the top row locations for execution in USER mode, the local label search is not performed for that particular reassigned location.  
Example: The following program, named SPEED, computes distance (given rate and time), rate (given distance and time), or time (given distance and rate). While in USER mode, you press A when you wish to compute a distance, B when you wish to compute a rate, and C when you wish to compute a time. The program prompts you for the required data. Since you assigned PROMPT to Σ+ for USER mode operation earlier in this section, simply press Σ+ in USER mode when you wish to load a PROMPT .
Keystrokes Display    
g GTO · · 
  00 REG 36    
g LBL 
  01 LBLTSPEED    
  The main program.
  01TA,B,OR C?    
  03 PROMPT    
  Prompts and stops for input.
g LBL 
  04 LBL A    
  Local label A.
   Execution of the normal functions on the top rows of keys in USER mode may take several seconds. The calculator must first search through the current program for the local label associated with that key. If no local label is found, the normal mode function is then executed. This is only true when no other function has been assigned to that key for USER execution. To shorten this search time, press g GTO · · .