HDF5 Datatypes
In HDF5, a datatype is an object that describes the storage format of the individual data points of a data set. There are two categories of datatypes; atomic and compound datatypes:
- Atomic datatypes cannot be decomposed into smaller units at the API level.
- Compound datatypes are a collection of one or more atomic types or small arrays of such types. Compound datatypes are similar to a struct in C or a common block in Fortran. See Compound Datatypes for additional details.
In addition, HDF5 uses the following terms for different datatype concepts:
- A named datatype is a datatype that is named and stored in a file. Naming is permanent; a datatype cannot be changed after being named. Named datatypes are created from in-memory datatypes using the H5T_COMMIT routine.
- An opaque datatype is a mechanism for describing data which cannot be otherwise described by HDF5. The only properties associated with opaque types are the size in bytes and an ASCII tag string. See Opaque Datatypes for additional details.
- An enumeration datatype is a one-to-one mapping between a set of symbols and an ordered set of integer values. The symbols are passed between IDL and the underlying HDF5 library as character strings. All the values for a particular enumeration datatype are of the same integer type. See Enumeration Datatypes for additional details.
- A variable length array datatype is a sequence of existing datatypes (atomic, variable length, or compound) which are not fixed in length from one dataset location to another. See Variable Length Array Datatypes for additional details.
