Program instruction mechanism for shortened recursive handling of

Abstract

Program instruction TPI (Test Pending Interruption) and associated data processor sequence controls for its execution enable interruption handling programs to operate in a shortened recursive mode relative to interruptions pending while such programs are in control of a data processor system. Execution of a TPI instruction sets a condition code distinguishing between pendency and non-pendency of a request for interruption in one associated class of interruptions. If an interruption request in that class is pending, the instruction execution controls clear (terminate) it. If more than one request is pending, a selected one is cleared. The selection is based on a predetermined priority ordering. Interruption code information is stored by the execution controls, indicating the source of the cleared request. The interruption handling program branches on the condition code and the interruption code information, to attend to the interruption task associated with the cleared request. Since that program is in control of the system when the TPI instruction is executed, the branch sequence may omit status saving operations and other operations associated with the handling of interruptions.