HDF is a multi-object file format that facilitates the transfer of various types of scientific data between machines and operating systems. HDF allows self-definitions of data content and easy extensibility for future enhancements or compatibility with other standard formats. HDF includes Fortran and C calling interfaces, and utilities to prepare raw image of data files or for use with other NCSA software. The HDF library contains interfaces for storing and retrieving compressed or uncompressed 8-bit and 24-bit raster images with palettes, n-Dimensional scientific datasets and binary tables. An interface is also included that allows arbitray grouping of other HDF objects.