Abstract: A method for protecting an operating environment on a processor from a rogue program operating on the processor comprising isolating simultaneously executing programs or operating systems is disclosed. Memory space for use only by the first program while the first program is executing is allocated. Communication between the first program and the computer's operating environment is accomplished through a single link employing one of several methods including using shared memory space, a dedicated interrupt or a dedicated I/O port. The monitor manages a restricted operating environment for the first program on the processor, the restricted operating environment preventing the first program from accessing resources on the processor except for the allocated memory space the single communication link.