RMS 01/10/76  THE PROGRAM X REMEMBERS A DDT COMMAND FOR YOU.
PREFIX A LINE OF DDT COMMANDS WITH ":X " TO EXECUTE THEM
AND SET :X'S MEMORY.  FROM THEN ON, JUST PLAIN ":X<CR>"
WILL RE-EXECUTE THEM.  Y AND XM ALSO EXIST, AND EACH REMEMBERS
ITS OWN COMMAND LINE. MORE CAN BE CREATED BY LINKING TO
SYS;TS X (FROM YOUR OWN DIRECTORY OR FROM SYS1;).
THE MEMORY IS ON DISK, IN A FILE WHOSE FIRST NAME IS
_X OR _Y OR _XM OR WHATEVER, AND WHOSE SECOND NAME IS YOUR UNAME.