From Wikipedia..."PDM (Programming development manager) was installed on most AS/400 and IBM System i systems as a part of the Applications Development ToolSet (ADT) and is still installed on most IBM i systems today. PDM is an environment that lets programmers and/or operators navigate three levels of the PDM: 1) the library level, 2) the object level, and 3) the member level."

From Ross...PDM is at the centre of the iSeries Application Development Toolkit. It organizes objects and source code in the iSeries libraries presenting the developer with a structured an coherent environment in which to work. PDM is the native and commonly used tool for developers working in he iSeries environment.