anchor.diff:  |LIST 100+ |Lists line 100 and the next 20 lines.
   |==========
   
  +LOAD
  +~~~~
  +
  +Loads a stored program into memory.
  +Sorts statements by line number.
  +Clears the current program prior to loading the new one.
  +
  +Syntax:	LOAD filename
  +
  +The 'filename' argument may be enclosed in quotes.
  +Quotes are necessary when the name contains a space character.
  +
  +NEW
  +~~~
  +
  +Clears the current program.
  +Does not ask to save a loaded program.
  +
  +Syntax:	NEW
  +
   PRETTY
   ~~~~~~
   
  
positive.code: 
  The second phase executes statements, starting with the lowest-numbered statement and following the path of execution.
  
  TRACE
  ~~~~~
  
  
negative.code: They have no line number.
  They are available only in "run" mode.
  
  CROSSREF
  ~~~~~~~~
  
  Lists the numeric constants, text constants, functions, and variables used in the program, along with the line numbers on which they appear.
  
  DELETE
  ~~~~~~
  
  Removes lines from the program.
  
  My experience with other BASIC interpreters is that lines can be deleted by simply typing a line number and pressing RETURN.
  (That is, entering an "empty" line with line number and nothing else.)
  That technique does not work with BASIC-1965, as BASIC-1965 allows empty lines to be part of a program.
  
  So how to remove a line from a program?
  Replacing a line with an empty line is possible, and certainly makes the offending line "go away" from execution, but what if we want to really remove a line?
  
  That's what the DELETE command does.
  
  DELETE uses the same specification as the LIST command.
  
  Syntax:	DELETE [line specification]
  
  If the list specification is a single line, it is deleted immediately.
  If the list specification is a range, the lines are displayed and the user must confirm the operation.
  
  The DELETE command with no specification (implying the entire program) does not delete the program but does nothing.
  (To delete the entire program, use the NEW command.)
  
  LIST
  ~~~~
  