This part discusses the additional requirements at software levels and operating system which will create the parallel programs run on parallel hardware. Collectively, these requirements define the parallel program development environment. A parallel programming environment consists of available hardware, operating system, supporting languages along with application programs and software tools. This part includes discussion of message passing systems, shared memory systems, vector processing; scalar, array superscalar, and pipeline processors and dataflow computers. This part also presents a case study regarding operating systems for parallel computers.