International Business Machines Corporation

Steven J Repka

Greg A Dyck

Brian B Moore

David E Lee

Gregory A Burke

A central processing unit of an information handling system is provided with a Trap instruction to facilitate transfer of control from a user program to a trap program. A dispatchable unit control block (DUCT) of the CPU is loaded with the address of a trap control block, which in turn contains the addresses of a trap save area and a trap program. The user program is provided with Trap instructions at the desired transfer points. Upon decoding a Trap instruction in the user program, the CPU saves state information from the program status word (PSW), general registers and access registers in the designated trap save area, loads the address of the trap control block into a general register, and copies the address of the trap program into the instruction address field of the PSW to transfer control to the trap program. Upon completion of execution, the trap program may issue a Resume Program (RP) instruction to restore the previously saved state information to return control to the user program.

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Hopewell Junction, NY, United States of America

Steven J Repka