A Datatype is a data representation consisting of atomic data types such as a string, byte, integer, floating point value of a given word size, or in the form of a C struct containing combinations of atomic types. A Datatype is used to describe the characteristics of one's data, and a number of Datatypes may collectively constitute a header. Every Datatype is given a name which is stored in a string; this string is used to represent the Datatype in the HDF file.