  We present a graphical simulation tool for visually and interactively
exploring the processing of various events handled by an operating system when
running a program. Our graphical simulator is available for use on the web and
locally by both instructors and students for purposes of pedagogy. Instructors
can use it for live demonstrations of course concepts in class, while students
can use it outside of class to explore the concepts. The graphical simulation
tool is implemented using the React library for the fancy ui elements of the
Node.js framework and is available as a single page web application at
https://cpudemo.azurewebsites.net. Assigning the development of the underling
text-based simulation engine, on which the graphical simulator runs, to
students as a course project is also an effective approach to teach students
the concepts. The goals of this paper are to showcase the demonstrative
capabilities of the tool for instruction, share student experiences in
developing the engine underlying the simulation, and to inspire its use by
other educators.
