Method and apparatus for handling masked exceptions in an instruction interpreter

A method and apparatus for handling masked exceptions that receives an exception from the operating system on which an emulator is running a user program and determines the origin of the exception. If the emulator generated the exception, the emulator handles the exception internally and returns it to the operating system. If the emulated user program generated the exception, the emulator checks the status of the exception type. If that type of exception is blocked, the exception is marked as deferred. Otherwise, the exception is delivered to the user application or marked as pending for later delivery. The system and method can maintain a virtual exception mask to indicate the status of the exception type.