The Slide Rule
The slide rule is a tool that has long since been outdated by computers. It performed simple multiplication and division problems, as well as trigonometrical equations and logarithms. The rule below is a working Java applet; to use it, simply slide the center piece or the glass to the left or right to position them, and the computer will calculate the result in relation to the cursor.
This is the Java Slide Rule
Java Slide Rule courtesy of System Source