1. A method of providing a supervisor for a data processing system utilizing a plurality of operating systems comprising the steps of: (a) identifying a data processing system state requiring activation of a different operating system; (b) safestoring contents of registers defining a state of a central processing unit of said data processing unit in a reserve memory associated with a currently active operating system; (c) addressing a reserve memory associated with said different operating system, (d) entering in said state defining registers of said central processing unit an address of said different operating system reserve memory, an address in a page table directory, data in registers of said central processing unit establishing a predetermined state of said data processing system, and data establishing a decor for said central processing unit determined by said different operating system; and (e) initiating operation of said different operating system.