ABOUT HDF 4.1 Release 5 
                               November 2001 

INTRODUCTION

This document describes the differences between HDF 4.1r4 and
HDF 4.1r5.  It is written for people who are familiar with
previous releases of HDF and wish to migrate to HDF 4.1r5.

The HDF 4.1r5 documentation can be found on the NCSA ftp server 
(ftp.ncsa.uiuc.edu) in the directory:

     /HDF/HDF/Documentation/HDF4.1r5/

First-time HDF users are encouraged to read the FAQ in this
release for more information about HDF.  Users can also look
at the home page for HDF at:

     http://hdf.ncsa.uiuc.edu/

If you have any questions or comments, please send them to:

     hdfhelp@ncsa.uiuc.edu

CONTENTS

- New Features and Changes
- Platforms Tested

New Features and Changes:
========================

o The following Vdata routines were added:

     VSsetblocksize/vsfsetblsz -- sets the block size of the 
                                  linked-block element.
     VSsetnumblocks/vsfsetnmbl -- sets the number of blocks for 
                                  a linked-block element.
     VSgetblockinfo/vsfgetblinfo -- retrieves the block size and the number 
                                    of blocks of a linked-block element.

o  Two routines were added to get compression information for the SD and
   GR interfaces, including chunked elements: SDgetcompress/sfgcompress 
   and GRgetcompress/mggcompress. 

   Note: 

   - For a JPEG image, GRgetcompress only returns the compression type, not 
     the compression information (i.e, quantity and force_baseline).  This 
     information is not currently retrievable.

   - Getting compression type for JPEG chunked images is not working yet.

o  "hdp dumpgr" has a new option, -pd, to print palette data only.  Also,
   whenever option -p or -pd is given, only palettes are printed, and no 
   images or file attributes. 

o  A new FORTRAN function, heprntf (HEprint), was added.  It takes two
   arguments: file name and level.  If the file name string has 0 length,
   then error messages will be printed to standard output. 

o  On Windows, the unresolved symbol (error_top) error has been fixed when 
   calling HEclear and linking with the DLL.  Users who want to use the HDF 
   DLL should define HDFAPDLL in their applications.  Simply go to Project 
   Settings and add HDFAPDLL as the predefined constant.

o  A memory leak in the netCDF portion of the HDF/mfhdf distribution
   was fixed. 

o  The "#define NULL" was removed since ANSI C compilers are required to
   define NULL.

o  When using "hdp dumpgr", data was being printed in the range of 0-250
   when it should have been between 0-168.  This problem is now fixed.

Please refer to the bugs_fixed.txt file for more details on bugs that were 
fixed.


Platforms Tested:
================

HDF 4.1 Release 5 has been tested on the following platforms:

   Cray SV1 10.0.0.8
   Cray T3E sn6711 2.0.5.55                     
   Compaq Tru64 Unix (OSF1) 5.1
   DEC Alpha/OpenVMS AXP 7.2-1
   FreeBSD 4.4
   HP-UX B.11.00 
   IBM SP 4.3
   IRIX 6.5 
   IRIX64 6.5 (-n32, -64)
   Linux 2.2.18smp
   Solaris 2.7, 2.8
   Windows NT/98/2000

For more information on the platforms that were tested and for
which we provide pre-compiled binaries, please refer to the following
web page (accessible from the HDF home page):

     http://hdf.ncsa.uiuc.edu/platforms.html