As its name implies, the Very Simple CPU simulator is a computer simulation package designed to illustrate the functioning of the Very Simple CPU, a four-instruction CPU presented in the textbook "Computer Systems Organization and Architecture" (by John D. Carpinelli, Addison-Wesley, 2001). The simulator allows the user to enter a simple program and assemble it, and then graphically illustrates the flow of data through the CPU's register section, ALU, and control unit. The user can simulate either a hardwired or a microcoded control unit. The simulator is a Java applet that can be run within any web browser on any computing platform. The simulator requires version 1.4.1 of the Java 2 VM, available for download at java.sun.com.