Nelson is an array programming language providing a powerful open computing environment for engineering and scientific applications using modern C/C++ libraries (Boost, Eigen, …) and others state of art numerical libraries.It has sophisticated data structures (including cell, struct, linear systems, …), an interpreter and a high level programming language.Nelson has been developped to be an open/modular system where an user can define these own data types and operations on these data types by using overload.