1. A processor comprising: a cache memory for normal programs which stores instructions required for running normal programs and a cache memory for exception programs which stores instructions required for running exception programs; and an instruction register which fetches instructions from either the cache memory for normal programs or the cache memory for exception programs, and stores the instructions, wherein the processor determines whether a currently running program is a normal program or an exception program and fetches instructions from either the cache memory for normal programs or the cache memory for exception programs according to a result of the determination, to input the fetched instructions to the instruction register.