Subst

SUBST is a command on the DOS, IBM OS/2 and Microsoft Windows operating systems used for substituting paths on physical and logical drives as virtual drives. It is similar to floating drives, a more general concept in operating systems of Digital Research origin, including CP/M-86 2.x, Personal CP/M-86 2.x, Concurrent DOS, Multiuser DOS, System Manager 7, REAL/32, as well as DOS Plus and DR DOS (up to 6.0).

The Windows SUBST command is available in supported versions of the command line interpreter CMD.EXE.

In Windows NT, SUBST uses DefineDosDevice() to create the disk mappings.

In MS-DOS SUBST was added with the release of MS-DOS 3.1.

The JOIN command is the "opposite" of SUBST, because JOIN will take a drive letter and make it appear as a directory.

Some versions of MS-DOS COMMAND.COM support the undocumented internal TRUENAME command which can display the "true name" of a file, i.e. the fully qualified name with drive, path, and extension, which is found possibly by name only via the PATH environment variable, or through SUBST, JOIN and ASSIGN filesystem mappings.

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