ALIAS command:	system command to set the p,pn to be used
when none is specified in an ENTER, LOOKUP, RENAME.
Forms:
ARG		MEANING
P,PN		Set alias p,pn to P,PN.
P		Set alias p to P, copy pn from normal p,pn (login).
<none>		Reset alias p,pn to normal p,pn (login).

ALIAS uuo:	uuo to set, reset, and get alias p,pn.
Calling:
	CALLI AC,400071
	      or
	CALL AC,['DSKPPN']
ARG (in AC)	MEANING
<legal job #>	Get alias for job #.
0		Get alias for current job.
-1		Reset alias for current job to normal p,pn.
≠0,,≠0		Set alias p,pn to contents of ac.
≠0,,0		Set alias p to left half of ac, copy pn from
		normal p,pn.