The Hierarchical Data Format is a general purpose library and
file format for storing scientific data.
HDF can store two primary objects: datasets and groups. A dataset is
essentially a multidimensional array of data elements, and a group is
a structure for organizing objects in an HDF file. 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. You can also mix and match them in HDF files
according to your needs.