HDF5 stands for version 5 of Hierarchical Data Format. When Version 5 was introduced, it was dubbed HDF5 to emphasize the fact that the new version was significantly different from previous versions of HDF and not backwards-compatible. Later, the HDF Group decided to adopt the name HDF4 for the earlier version to avoid confusion. HDF5 was designed to address some of the limitations of the HDF 4.x library and current and anticipated requirements.
HDF5 is a general purpose library and file format for storing scientific data. HDF5 can store two primary types of objects: datasets and groups. A dataset is essentially a multidimensional array of data elements, and a group is a structure for organizing objects within the HDF5 file. (These two are roughly analogous to files and directories, respectively, in a conventional filesystem, and, indeed, objects in an HDF5 file may be referenced by a Unix-style path.) Using these two basic objects, one can create and store almost any kind of scientific data structure, such as images, arrays of vectors, and structured and unstructured grids. They can be mixed and matched in HDF5 files according to user needs. HDF5 does not limit the size of files or the size or number of objects in a file.
- HDF5 Specification Latest official specification from The HDF Group. As of November 2012, Version is 2.0.