Patent US 6,301,702

An instruction decoder decodes an instruction code, whereupon immediate data, if included, is searched to see whether it is encoded or not. After decoding, an operation code in the instruction code is informed to the execution unit. If the instruction code includes immediate data, the data is transmitted to a data decoder to be decoded according to a given rule. The decoded data is transmitted to the execution unit. Because the immediate data is reduced in size through encoding, the number of times instructions are fetched is accordingly reduced, which resultantly increases processing efficiency. Since an entire instruction code is also reduced in size, a wider variety of operations are instructed using the same instruction code format.