logisim-evolution

Logisim-evolution is educational software for designing and simulating digital logic circuits.
Logisim-evolution is free, open-source, and cross-platform.

Project highlights:
* easy to use circuit designer,
* logic circuit simulations,
* chronogram (to see the evolution of signals in your circuit),
* electronic board integration (schematics can be simulated on real hardware),
* VHDL components (components behavior can be specified in VHDL!),
* TCL/TK console (interfaces between the circuit and the user),
* huge library of components (LEDs, TTLs, switches, SoCs),
* supports multiple languages,
* and more!