SIMH

Simh (which stands for Simulation and Hardware) is a computer program that is used to make a model or replica of a real computer system, so people can use it to practise or experiment with different computer systems without actually using a real one. It works by taking the real computer system's features and making them into a computer program that runs on your own computer. When you run the program, it behaves just like the real computer system, so you can simulate and try out different things on the system.