HDF4

At its lowest level, HDF is a physical file format for storing scientific data. At its highest level, HDF is a collection of utilities and applications for manipulating, viewing, and analyzing data in HDF files. Between these levels, HDF is a software library that provides high-level APIs and a low-level data interface.

The Application Programming Interfaces

These include sets of routines for storing and accessing a specific type of data. Although each interface (Application Programming Interface or API) requires programming, all the low-level details can be ignored. These are available in both C and Fortran.
The data structure types that HDF supports are Scientific Data Sets (SD and DFSD APIs), Raster Images (General, 8-bit, 24-bit APIs), color palettes, text entries, and Vdatas and Vgroups.

Copyright Notice and License Terms for HDF Software Library and Utilities