From: thefadden@gmail.com   
      
   Take a look at RENUMBER from the DOS 3.3 System Master disk.   
      
   [...]   
    1200  HOME : PRINT  TAB( 4)"RENUMBER IS INSTALLED AND READY"   
    1210  VTAB 8: PRINT "IF YOU USE 'FP', 'HIMEM', OR 'MAXFILES'"   
    1220  PRINT : PRINT "  YOU WILL HAVE TO RE-RUN RENUMBER"   
    10000  REM  DO NOT CHANGE 10010   
    10010  CALL  PEEK (121) +  PEEK (122) * 256 + 31   
      
   It's looking at $79-7a (OLDTEXT), which holds a pointer to the end of the   
   previous line.  The machine-language code follows the last line, so really the   
   comment should be, "do not change 10010, or add anything after this line".  So   
   long as you follow    
   that rule, you can add or remove lines, and everything just gets moved around.   
      
   The code it calls relocates itself below DOS and sets up the ampersand vector.   
      
   One reason to use this sort of approach is for programs on cassette tape.    
   Binary programs must be loaded with an explicit start and length, but BASIC   
   programs can just use LOAD/SAVE.   
      
   (For Integer BASIC, see https://retrocomputing.stackexchange.com/q/494/56 .)   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)