1. A method for emulating code from an original computer system on a host computer system, the method comprising the steps of: fetching a program instruction associated with program code to be emulated on a host computer system; determining whether the program instruction is to be executed natively on the host computer system or is to be emulated on the host computer system; and if the program instruction is to be executed natively on the host computer system, emitting a native code fragment associated with the program instruction into a dynamic execution layer interface to be executed.