A computer system including: a memory configured to store various kinds of data; a use setting data memory means for storing use setting data indicating a use of each of a plurality of memory blocks into which the memory is divided by a certain length; a memory diagnosis means for diagnosing the memory so as to detect a bad area in each of the memory blocks; and a memory use setting means for setting the use setting data of each of the memory blocks stored in the use setting data memory means in accordance with a result of detecting the bad area in each of the memory blocks by means of the memory diagnosis means.