ClassicLadder is described as 'An open source project to have a free ladder and sequential (grafcet) programming software coded in C language (to be used for educational as PLC Simulator, training, in Software PLC on PC computers or embedded platforms, ...)'. There are six alternatives to ClassicLadder for Windows, Linux and Mac. The best alternative is 4diac, which is both free and Open Source. Other great apps like ClassicLadder are CODESYS (Free Personal), TIA Portal (Paid), LOGO! Soft Comfort (Paid) and Automgen (Paid).
CODESYS is the leading manufacturer-independent IEC 61131-3 automation software for engineering control systems. It is used to program many hundreds of different controllers, PLCs, PACs and other automation system, even via an Industry 4.0 interface.
TIA Portal is the key to unlocking the full potential of Totally Integrated Automation (TIA). The pioneering engineering framework optimizes all planning, machine and process procedures and offers a standardized and integrated operating concept.
LOGO! Soft Comfort is software for programming simple Siemens LOGO! PLCs. Programming is done in one of two graphical programming languages - FBD (Function Block Diagram) or LAD (Ladder Diagram). Simulation and online monitoring is available.
Outseal PLC is an IDE in the form of Ladder Diagrams based on Arduino Board. This PLC has hardware that is open to the public, you can download and learn the electronic circuit freely and make yourself at home at an affordable price.