http://engineers-excel.com/Tools/Little%20Man%20Computer/Description.htm
This tool shows the working of a computer CPU using the Little Man Computer Model (LMC).
The Little Man Computer was created by Dr. Stuart Madnick of MIT as a model for teaching the workings of a CPU. The LMC models the working of a modern CPU, but is still simple enough to be understood and programmed by high school students.
