RISC processor [Reduced Instruction Set Computer], computer arithmetic-logic unit that uses a minimal instruction set, emphasizing the instructions used most often and optimizing them for the fastest possible execution. Software for RISC processors must handle more operations than traditional CISC [Complex Instruction Set Computer] processors, but RISC processors have advantages in applications that benefit from faster instruction execution, such as engineering and graphics workstations and parallel-processing systems. They are also less costly to design, test, and manufacture. In the mid-1990s RISC processors began to be used in personal computers instead of the CISC processors that had been used since the introduction of the microprocessor.