This is the public release of version 1.0 of SDF ("Self Describing Files" or "Super-Duper Files, depending on how impressed you are). It is the first version of the last I/O package you'll ever need. SDF files are binary data files with an optional header which contains 1) a description of the layout of the data, and 2) optional ascii constants. There is no output capability because the SDF files are so easy to write :-). SDF has been used to manage the configuration and output of large parallel simulations for over 20 years.