This module is about derived datatypes in MPI. It describes how to use derived datatypes as they are implemented in the MPI-1 standard. You should be warned that the MPI-2 standard has made more changes in this area of MPI than in any other part. Many of the calls and syntax that we have in MPI-1 have been deprecated in the MPI-2 standard and other calls have been put in their place. However, the principle of MPI is that any program that works in MPI-1 will also work in MPI-2. So, a program you write using the information in this module should work in the future, but if you are using an implementation of the MPI-2 standard, it would be better to start out using the new syntax.