Concealing Logical Names

  You can specify that a logical name be defined as concealed.
  You can conceal logical names that refer to devices or
  directories.

  When you assign a logical name to a device, concealing the
  logical name allows you to write programs and command
  procedures and perform other operations without being
  concerned about which physical device actually holds the disk
  or tape.

  When you assign a logical name to a directory or
  subdirectory, concealing the logical name can make the
  directory or subdirectory appear as the master file directory
  for the current device.  This directory or subdirectory to
  which you assign a concealed logical name is called the root
  directory.  You can then use this root directory as the base
  from which to access directories beneath it.