"program manager" title has a long of history, it existed way before Microsoft was around. In the 1st half of 20th century, the common use of the word "program" was to describe an allocation of resources like manpower, production capacity, equipment, typically in the military setting. For example, the term "linear programming" as a mathematical optimization technique is based on using "programming" in the sense of allocating resources.<p>So historically, program managers handled decisions about how to allocate resources to accomplish a mission. These days, program managers usually allocate resources over a portfolio of projects and decide whether projects are helping to achieve the program's mission.<p>Product manager has a responsibility for one or more products and associated strategic and executive decisions , around business plan, marketing, sales, research and development.