Patent ID: 7054990

Claim:
An external storage device connectable to a host computer, comprising: a non-volatile semiconductor memory; an interface to connect to the host computer; and a controller to access the non-volatile semiconductor memory in response to a command and an address from the host computer; wherein said non-volatile semiconductor memory is divided into plural areas; wherein a first command for accessing a first area among said plural areas of the non-volatile semiconductor memory is different from a second command for accessing a second area among said plural areas of the non-volatile semiconductor memory; wherein the controller determines whether the command from the host computer is the first command or the second command, wherein, when the command is the first command, the controller carries out first command processing to a sector of the first area in accordance with the address from the host computer; and wherein, when the command is the second command, the controller carries out second command processing to a sector of the second area in accordance with the address from the host computer, further comprising information indicative of the plural areas of the non-volatile semiconductor memory, the external storage device dynamically changing the sizes of the first and second areas of the non-volatile semiconductor memory on the basis of an instruction of the host computer by a part which rewrites the information indicating of the plural areas of the non-volatile semiconductor memory.