CALL_EXTERNAL routines
			    ======================

This directory contains C software to support IDL routines using CALL_EXTERNAL.
The IDL procedure files themselves are in other directories within the CDS
software tree.

There are makefiles in this directory for various operating systems, as well as
a MAKE.COM file and option files for VMS (not recently tested).  For example,
under OSF one would type

	make -f Makefile.osf

Currently supported operating systems are Linux, OSF, VMS, and SunOS.  Other
operating systems would require additional makefiles or equivalents.
CALL_EXTERNAL is not supported under Ultrix.

In order to use this software, the environment variable (VMS: logical name)
CDS_EXTERNAL must be defined to point to the file created when the software is
compiled.  Generally, in Unix this is a file called "external.so" (although
some versions of Unix act differently).  In VMS it is EXTERNAL.EXE.

The CDS IDL procedure files are written so as to use CALL_EXTERNAL only when
the enviroment variable CDS_EXTERNAL is defined, and to use some other
procedure (or return an error) when it is not defined.

Currently, the only routine supported are rearrange.pro, check_sum.pro, and
fmedian.pro, although other routines may be added in the future.

The "fortran" subdirectory contains an earlier version, in which FMEDIAN was
implemented through FORTRAN rather than C.