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Logic Simulator

New version: https://github.com/codepiet/LogicSim3


With LogicSim you can design and simulate digital logic circuits with logic gates like AND, OR, FlipFlop, etc.
The following types of logic gates are included:
  • Basic: AND, NAND, OR, NOR, XOR (Antivalence), Equivalence, NOT
  • Flip Flops: RS, D, T, JK, JKMS
  • Timers: clock generator, MonoFlop, Turn on delay, Turn off delay
  • Inputs: Switch, number-input for decimal and hexadecimal values
  • Outputs: LED, LCD for decimal and hexadecimal values
You can create your own gates by saving a circuit as a "module" and reuse this module in another circuit.

Version history

  • 2009-07-16
    Polish translation by Wieslaw Soltes
  • 2009-01-09, Version 2.4
    PNG export
    Changes by Dieter Meier:
    • stop simulation when new file is opened
    • reset stopped simulation
    • D FlipFlop with reset
    • circuits BCD Adder and BCD Counte, modules segm1-7
  • 2008-11-22
    updated D-FlipFlop, Swedish translation and documentation
  • 2008-06-30
    changed images for DFF, JKMSFF, JKCFF
    added Dutch translation, by Ben Harkema
    fixed some layout problems on OS X
  • 2007-08-02
    LogicSim can now run as applet in browser
  • 2007-06-13
    Added reset button
  • 2006-06-01
    New component: 7-segment display
  • 2006-05-30
    Added French localization and manual, created by Thierry Valette
  • 2006-01-19
    Added Italian localization and manual, created by Prof. Riccardo Bianchi
  • 2006-01-02, Version 2.1
    ISO gates Internationalization support, german localization
    ISO gate symbols, created by Prof. Riccardo Bianchi
    Properties item in gate context menu is now disabled when gate has no properties
    The Switch element can now be configured to be a traditional toggle button or a click button, which ist only on as long as the mouse button is held down.
  • 2004-09-26
    Text label Added support for text labels anywhere in the circuit.
    Place the text label object and edit the text with context menu -> properties. Use \ (Backslash) to insert a line break.
  • 2001, Version 2.0
    JAVA-Version of LogicSim
    added support for "modules", you can save a circuit as module and reuse it in another circuit
  • 1995-1996, Version 1.0
    Initial Version for Amiga, written in "PCQ-Pascal". LogicSim for Amiga


 download LogicSim
To start LogicSim, extract the archive content and double click on LogicSim.jar or run "java -jar LogicSim.jar".
 download LogicSim source

This program is free software released under the GNU General Public License.

 English LogicSim Manual
 Deutsche LogicSim Anleitung

To run this program you need at least version 1.4 of the JAVA Runtime Environment.
 download the latest Java Runtime Environment (JRE)


Demo Applet

See LogicSim in action: LogicSim Applet


5 Bit Adder
Simulation of a 5 Bit Adder with decimal input/output.

Full Adder
The Full Adder module used in the top circuit.