Logisim

Logisim is a logic simulator which permits circuits to be designed and simulated using a graphical user interface. Released under the GNU Public License, Logisim is free software designed to run under the Microsoft Windows, OS X, and Linux platforms. Its code is entirely in Java using the Swing graphical user interface library. The primary developer, Carl Burch, has worked on Logisim since its inception in 2001.

The software is used most often by students in computer science classes to design and experiment with digital circuits in simulation. Circuits are designed in Logisim using a graphical user interface similar to traditional drawing programs, an interface also found in many other simulators. Unlike most other simulators of Logisim's sophistication, Logisim allows the user to edit the circuit during simulation. The relative simplicity of the interface makes it work well for survey courses. Design features for more sophisticated circuits, such as the "subcircuits" and "wire bundles" found in Logisim, are available in few other open-source graphical tools.

While users can design complete CPU implementations within Logisim, the software is designed primarily for educational use. Professionals typically design such large-scale circuits using a hardware description language such as Verilog or VHDL. Logisim is unable to accommodate analog components.

Logisim has been indefinitely suspended in development, but a fork, called Logisim-evolution, is still actively developed.