process - How to save a program's progress, and resume later? -

You can learn a lot of programs, like some password cracking programs, we can stop them while running, and when we Run the program again (without entering or input the same input), they will be able to move forward from where they are left. I wonder what kind of technology are those programs using?

[edit] I'm writing a program mainly based on the recursive functions. Within my knowledge, I think it is incredibly difficult to save such states in my program. Is there a technique, somehow, stack content, function calls and saves the data contained in my program, and then when it is restarted, can it stop it as if it has been stopped? These are just some concepts that were in my mind, so please forgive me if it does not understand ...

This will be different for each program. For some, say, something like a cruel power password cracker will actually need to be saved for the last password tried for other apps You may need to store many data points, but in fact All this is very much: saving and loading the minimum amount needed for rebuilding where you were.

Another general technique image of the whole program state. If you've ever played with the ability to save the state with a game console emulator, then this is what it does. There is a similar technique available for pickling in the cassation. If the environment is sufficiently stable (i.e.: no different signal) you only copy entire app memory state into a binary file. When you want to start over again, you copy it back to the memory and start running again. It gives you near real estate recovery, but it is possible that it is very high environmental / language dependent or not. (For example: Most C + apps could not do this without help from OS or if it was made keeping in mind it very carefully.)