Substitutes a virtual drive letter for a path designation.

Use the SUBST command to substitute a drive letter for a path in order to treat a virtual drive (a reserved area rather than an actual disk drive) as a physical drive.

In order to enter drive designations using any letter (other than just the letters for the physical drives installed in your computer), you may have to add this line to a CONFIG.SYS file that should be placed in the root directory of your startup drive:

LASTDRIVE=Z

Six DOS commands cannot be used with virtual drives created with the SUBST command. They are:

CHKDSK
DISKCOPY
FDISK
FORMAT
LABEL
SYS

If you enter the SUBST command without options , the program will display the name of the current virtual drives that are in effect (if any).

For more information on SUBST and other hard disk commands, see Chapter 3, Using Fixed Disks, in the downloadable book DOS the Easy Way.

Example

To create a virtual drive F for the path, SALES\LETTERS (under the root directory) of drive C, enter

subst f: c:\sales\letters

Read and write requests to either drive F or to C:\SALES\LETTERS will be stored in the C:\SALES\LETTERS directory area.

Credit: http://www.easydos.com/subst.html

Nir.