@section Basic structure

The directory structure of @vxl{x} is below
@example
  $VXLSRC/vcl
          core/vnl
              /vul
              /vbl
              /vil
              /vgl
              /vsl
             @dots{}
          v3p/netlib
             /jpeg
             @dots{}
          config/cmake
          contrib/
@end example

@table @samp
@item vcl
is the C++ compatibility layer (@pxref{vcl}).

@item core
contains the core @vxl{x} libraries.

@item v3p
(v-third-party) contains code that is available elsewhere and is used
in implementing @vxl{x}. @code{v3p/netlib} contains cleaned-up C
versions of the high-quality Fortran code. @code{v3p/jpeg} and others
contain image file format code used by vil. In theory, you don't need
any of the v3p libraries if you have locally installed versions. In
practice, you need @code{v3p/netlib} but not the others.  the

@item config/cmake
contains the configuration files used by the CMake build system
(@pxref{CMake}).

@end table

@anchor{struct_other_packages}
@section Other packages

On the repository and some @vxl{x} distributions, you will find several other
packages in the @samp{contrib} directory.

@cindex gel
@cindex oxl
@cindex mul
@cindex rpl
@cindex brl
@cindex tbl
@cindex oul

@table @samp
@item gel
Published libraries from General Electric Global Research.
@item oxl
Published libraries from the Robots Research
Group at Oxford University.
@item mul
Published libraries from Imaging Science and Biomedical Engineering
at the University of Manchester.
@item rpl
Published libraries from Rensselaer Polytechnic
Institute
@item brl
Published libraries from Brown University
@item tbl
A set of image processing libraries.
@item oul
Published libraries from Otago University
@item conversions
A set of routines for converting between various @vxl{x} and non-@vxl{x} types.
@end table

These modules are presented as useful code, with even less guarantees
than @vxl{x} (which is not to suggest that we guarantee anything about
@vxl{x}).  In particular they may not work as advertised. They may not
be documented. If you find them useful, and think they deserve full
@vxl{x}-status please contact the library's author to see about having
the code tidied up and promoted to @vxl{x}.

You can find any overview documentation about these modules from the
@uref{https://vxl.github.io/,vxl homepage} by following the
``documentation'' link.

@section Subversion (svn) Repository

The VXL repository is provided by GitHUb! The
instructions for downloading @vxl{x} are documented at
@url{https://vxl.github.io/#download}.