format  Sint32 CDC_ChgDir (Sint32 filtno, Sint32 fid)
 Input  filtno: Aperture number
:  fid: File identifier of the directory file (CDC_NUL_FID: root directory)
 Output  None
 Function value  Returns an error code.
 End flag  EFLS flag
 Function  Moves the current directory to the directory indicated by the specified file identifier. Phi
If you specify CDC_NUL_FID for the  identifier, you will move to the root directory.
  Move to read the directory record and hold up to 254 file information from the beginning.
.  (Up to 256 including yourself and parents)
  If the file identifier does not point to a directory, REJECT is returned.
 Remarks  The CD block file system uses a selector for work. Work selector is aperture
 Specify by  number. 

 format  Sint32 CDC_ReadDir (Sint32 filtno, Sint32 fid)
 Input  filtno: Aperture number
 Output  None
 Function value  Returns an error code.
 End flag  EFLS flag
 Function  Reads the directory record of the current directory, and after the specified file identifier
  Holds up to 254 file information. (You and your parents always keep)
 Remarks  The CD block file system uses a selector for work. The working selector
 Specify by  number.