A memory device includes an unmapped read control module and a page buffer. The unmapped read control module is configured to receive a read command from a host, determine whether the read command is an unmapped read command, and output a memset command when the read command is the unmapped read command. The page buffer is configured to generate unmapped data by performing a memset operation in response to the memset command. The memset operation does not include a read operation for a memory cell array.