history n   displays the n most recent lines read by M.  With no arguments,
	    all the lines remembered by M are displayed.  If output redirection
	    is used (via > or >>), the lines are written without leading
	    numbers.  This is useful for producing files suitable for re-
	    execution by M.

	    Lines can be recalled using ! as the first character on a line
	    similiar to history substitution in the Unix csh.  !! recalls the
	    previous line.  Lines may be recalled by specifying their number
	    as shown by `history' or by their starting string of characters.