SUBST is an old DOS command, dating to the introduction of directories in DOS 2.0.

  Many DOS 1.x applications were written to operate on a current
*drive*.  The SUBST command allows a directory ("folder") to appear
as a drive letter, as a way of letting these applications run in a
more advanced environment than they were designed for.

  Microsoft has been warning against using this for the last several
DOS releases....

  In this case, the user is assigning an alternate drive letter to
the root directory on C:.  It's not obvious that there is any use to
this; specifically, no "mirroring" or duplication is being done.

David G


On 29 Jun 00, at 20:14, Chris Rivenbark wrote:

> Good evening ladies and gentlemen.
>
> I ran across something I haven't seen b4 today.  A user's
> autoexec.bat file had the following statement:
>
> subst L: C:\
>
> This statement in the autoexec.bat causes the C: drive to show up
> again as an identical drive w/ drive letter L: (in MY COMPUTER -
> Windows 98).
>
> What function does this serve?  Is it actually "mirroring" the
> drive?  If so, where is the image?

> Is this a security measure of some sort?

> Does Windows "see" the L drive as another drive w/ a Windows
> installation (I've seen this cause problems) or does it ignore it?

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