COMPUTER SYSTEM

PROBLEM TO BE SOLVED: To prevent data dependency and to execute a plurality of instructions at the same time. SOLUTION: The processor of the computer system includes a register renaming system composed of a temporary buffer 116 which includes a plurality of storage locations for storing an execution result in one of the storage locations in an instruction window and tag assigning logic 122 which receives a data dependency result from a data dependency inspecting means 108 and outputs a tag instead of a register address for the operand of a 1st instruction when the operand of the first instruction depends upon that of the last instruction among the instructions in the instruction window, which tag indicates the address of the operand in one of the storage locations.