New I-beams:

	1I'file name'		-Switch input to 'file name'.
	1I0			-Switch input back to the terminal.

	2I'file name'		-Switch output to 'file name'.
	2I0			-Switch output back to the terminal.

	3I'file name'		-Switch output to 'file name'. If the
				 file exists, append to it.
	3I0			-Switch output back to the terminal.

	10I 'UNIX command'	-Execute the command as if it were
				 typed in to UNIX.

In the above examples, the zero could have also been a null vector.

Example:

	If OUTPUTFILE is a character vector which contains a file name,
the file could be printed by the command:

	10I'pr -l64 ',OUTPUTFILE,' | opr -lp'
