All information related to the hardware simulator SIM-PL is placed here.

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SIM-PL is an educational tool for designing and simulating digital logic circuits. With the capacity to build in a hierarchical manner complex components from elementairy components, and to draw bundles of wires with a single mouse drag. SIM-PL can be used (and is used) to design and simulate entire CPUs for educational purposes.

With the simple toolbar interface of the design- and simulation-tool it is simple enough to facilitate learning the most basic and more indepth concepts related to logic circuits and computer architectures.

SIM-PL is used by students at colleges and universities around the world, ranging from a brief unit on logic in general-education computer science surveys, to computer organization courses, to full-semester courses on computer architecture.

SIM-PL sources are made ​​available under the GNU General Public License.


  • It is free of charge!
  • It runs on any machine supporting Java 5 or later.
  • There is a web based version too.
  • It includes circuit components include inputs and outputs, gates, multiplexers, arithmetic circuits, flip-flops, and RAM memory.
  • It is a complete authoring environment.
  • The editor:
    • Is based on a simple rubber band drawing principle
    • Editing is posible in a drawing window or in the hierarchical objects list
  • The simulator:
    • Contains a block diagram, program editor and time sequence diagram window.
    • The windows are free configurable.

Hystory in a nutshell

In 1994 the first computer organization & architecture course started with a comparable format as the current one. At that time there was no real pressure on finding a proper simulator. It changed when I switched to a different book in 1999. However, back then simulators suitable for teaching were sparse. The question was whether we should build a homemade simulator. While pondering about this question a simulator with a spartanic ascii character-based gui was still used.

In 2001 a freshman listening to the name of Wouter Koolen could no longer bear it. He proposed to write a much better simulator. I must admit that I was quite surprised. Especially when he said: "Next week I will have a first version.

In 2011 Wouter Koolen stepped back, not completely, after a decade being the sole developper of SIM-PL and produced during that time a full blown authoring environment. Anybody who made additions to, or build new architectures  with SIM-PL has noticed that Wouter is still willing to contribute.