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Uncovering the mechanics of The Games: Winter Challenge
An investigation into The Games; Winter Challenge
Whenever a program wants to interact with something outside it’s own code, it would call an interrupt and ask DOS to perform that task for it, handing back control to the operating system temporarily, and resuming when it is complete. Apart from the random memory allocation and deallocation providing some red herrings, the actual checking logic is fairly straight-forward and directly simulates how the physical code wheel functions. The fourth case is just a helper, it hooks the next interrupt after the dialog is closed, and overrides two bytes at the end of the routine that checks the provided input to inject an artificial int 3f instruction there.
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