anchor.diff:  They have no line number.
   They are available only in "run" mode.
   
  -NEW
  -~~~
  -
  -Clears the current program.
  -Does not ask to save a loaded program.
  -
  -Syntax:	NEW
  -
  -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
  +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
   ~~~~
  
positive.code: Syntax:	PRETTY [line specification]
  
  The line specification is the same as the line specification for the LIST command.
  
  TOKENS
  ~~~~~~
  
  Lists the current program and for each line displays the tokens identified on that line.
  
  Syntax: TOKENS [line specification]
  
  The line specification is the same as the line specification for the LIST command.
  
  CROSSREF
  ~~~~~~~~
  
  Lists the numeric constants, text constants, functions, and variables used in the program, along with the line numbers on which they appear.
  
  PROFILE
  ~~~~~~~
  
negative.code: READ displays the values read.
  LET displays the new value assigned.
  IF displays the two values, the operator, and the result ('true' or 'false').
  
  Variables
  ---------
  