The ASSIGN command redirects all disk operations for a given disk drive to
another drive.  The command format is as follows:

      ASSIGN [s=d [...]]

The assignment means that all disk accesses to the source drive "s" are
redirected to the destination drive "d".  Only the drive letter may be
specified (the colon ":" must not be specified).  If the command is
executed without parameters, all disk drive assignments are restored to
their normal defaults (ie. A=A, B=B, C=C, ...).

This command is particularly useful if you have a fixed disk.  Programs that
automatically read from a certain floppy may be redirected to the fixed disk
with the command  ASSIGN A=C B=C.

The "undo reassignment" command  ASSIGN  will be necessary to format floppy
diskettes and backup the fixed disk because DOS generates error messages
if there is an assignment present.  It's also much safer to format without
redirection, where it is perfectly clear which drive is going to be used.

The commands DISKCOPY and DISKCOMP ignore any device reassignments.
ckslashes takes you up one directory level.  This
  mechanism works for many DOS commands