Processor for executing instruction codes of two different lengths and device for inputting the instruction codes

For a processor having instruction codes of two instruction lengths (16 bits and 32 bits), methods of locating the instruction codes are limited to two types: (1) two 16-bit instruction codes are stored within 32-bit word boundaries, and (2) a single 32-bit instruction code is stored intactly within the 32-bit word boundaries. A branch destination address is specified only on the 32-bit word boundary. The MSB of each instruction code serves as a 1-bit instruction length identifier for controlling the execution sequence of the instruction codes. This provides two transfer paths from an instruction fetch portion to an instruction decode portion within the processor, achieving reduction in code side and in the amount of hardware and, accordingly, the increase in operating speed.