Date: 5 Feb 2002 22:03:03 -0400

 Under any DOS since DOS 2.0, you can put the following command into your
 AUTOEXEC.BAT file:

 assign b=a

 Then, when you type "dir b:" you'll no longer get the annoying prompt to
 insert diskette B (and the even more annoying prompt to insert A the
 next time you type "dir a:").

 You may be wondering why anybody would want to do this. Suppose you use
 two different machines, maybe one at home and one at work. One of them
 has only a 3.5" diskette drive; the other machine has two drives, and b:
 is the 3.5" one. You're bound to type "dir b:" on the first one, and get
 the nuisance message:

 Insert diskette for drive B: and press any key when ready.

 But if you assign drive b: to point to a:, you avoid this problem.

 Caution: there are a few commands, such as DISKCOPY, that will not work
 right on ASSIGNed or SUBSTed drives. See the DOS manual for the full
 list. Before typing one of those commands, be sure to turn off the
 mapping by typing "assign" without arguments.

 The DOS 5.0 manual says that ASSIGN is obsolete, and recommends the
 equivalent form of SUBST: "subst b: a:\". Unfortunately, if this command
 is executed when a: doesn't hold a diskette, the command fails. ASSIGN
 doesn't have this problem, so under DOS 5.0 you should disregard that
 particular bit of advice in the manual.