If a Operating System is present then the Operating System is sent an interrupt through Vector MACVAX at IPL 23 with the Command RESET_PROCESS in IPR(MVCR) (see MacVAX interrupt Vector). What happens at this point is dependant on the OS.
Without A System
If a process is loaded then all files opened by the process are closed and the processor is initialized. The process is then reloaded from the original file. If the file has changed, then the new file contents and symbol table are loaded. If the file is no longer present, then the call returns without performing the reset.