His father was a chemical engineer involved in research and development related to petroleum refining, paper production, and air pollution control systems.

In the late 1960s his family relocated from the San Francisco Bay Area to the small town of Eureka, California.

While at HP Sassenrath became interested in minimizing the high complexity found in most operating systems of that time and set out to formulate his own concepts of a microkernel-based OS.

In late 1981 and early 1982, Sassenrath took an academic leave to do atmospheric physics research for National Science Foundation at Amundsen–Scott South Pole Station.

Later in 1982, impressed by the new computing ideas being published from Xerox PARC, Sassenrath formed an HP project to develop the modern style of window-based mouse-driven GUIs.

Probus clearly demonstrated the power of graphical user interfaces, and the system also incorporated hyperlinks and early distributed computing concepts.

As a sophisticated computer for its day (Amiga used 28 DMA channels along with multiple coprocessors), Sassenrath decided to create a preemptive multitasking operating system within a microkernel design.

This design gave the Amiga OS a great extensibility and flexibility within the limited memory capacity of computers in the 1980s.

After the release of the Amiga in 1985, Sassenrath left Commodore-Amiga to pursue new programming language design ideas that he had been contemplating since his university days.

In 1986, Sassenrath was recruited to Apple Computer's Advanced Technology Group (ATG) to invent the next generation of operating systems.

[3] Sassenrath lives in Ukiah, California, where he grows grapes and makes wine, and is interested in amateur radio, video production, quantum electrodynamics, and boating.