- The File Handlers Table:
  - The mapping of file extensions to the class to handle the file is stored in the file handlers table (`REG.HANDLERS.FILE`)

        nM> res reg.handlers.file
          T: REG.HANDLERS.FILE = Table of 34 entries
        20S:  TMP            = nxm.sys.lib.DataFile
        20S:  RAW            = nxm.sys.lib.BaseFile
        20S:  PRM            = nxm.sys.lib.DataFile
        20S:  PKT            = nxm.sys.lib.DataFile
        20S:  SET            = nxm.sys.lib.DataFile
        20S:  MCR            = nxm.sys.lib.DataFile
        20S:  DAT            = nxm.sys.lib.DataFile
        ...

  - The handlers table is extensible.
    - New file types and handlers can be added or previously defined file types overridden.