External files are files whose
format is determined by the operating environment rather than by SAS
software. External files include raw data files, JCL libraries, files
that contain SAS programming statements, load libraries, and UFS files,
which are part of UNIX System Services (USS). In batch and noninteractive
line modes, the SAS log and procedure output files are also external
files.
Note: If you are using files in
the UFS file system, SAS views the
z/OS file system (zFS) and the
Hierarchical File System (HFS) as functionally equivalent.