If the fileref is a DATA step character variable with a blank value and a minimum length of 8 characters, a fileref is generated for you. Specifying a blank file-name deassigns one that was assigned previously. DISK specifies that the device is a disk drive. PIPE specifies an unnamed pipe.
TAPE specifies a tape drive.
TEMP creates a temporary file that exists only as long as the filename is assigned. The temporary file can be accessed only through the logical name and is available only while the logical name exists. If you do, SAS returns an error. Files manipulated by the TEMP device can have the same attributes and behave identically to DISK files. For details, see the SAS documentation for your operating environment.