CENTRAL ARITHMETIC PROCESSING UNIT AND INFORMATION PROCESSING SYSTEM

PURPOSE: To reduce the data transfer frequency of a CPU and also to improve the throughput of the CPU. CONSTITUTION: When the data stored in plural internal registers 4 are transferred to the outside, the data stored in some of registers 4 storing the data to be transferred are compounded together at a data compounding part 5 by a single instruction and then transferred to the outside via an arithmetic part 6 and a store buffer 7 as the data consisting of plural effective data parts of different attributes. When these data are transferred from the outside, the effective data parts are separated from each other by a single instruction. A zero addition part 2 adds the zero bits accordant with the length of registers 4 to the data, and a load selector 3 stores the data in some registers 4. As the hardware is prepared for execution of the separating and compounding operations, the data consisting of plural effective data parts can be transferred by a single instruction.