Abstract: A storage device includes: a memory device including a plurality of memory cells configured to store data and a plurality of word lines connected to the plurality of memory cells and a memory controller in communication with the memory device and configured to control the memory device, including controlling the memory device to perform a read operation perform, upon a failure of the read operation on the memory cell, a read retry operation by changing the read voltage based on a history read table, and wherein the memory controller is further configured to update the history read table, upon a success of the read retry operation, based on whether the word line connected to the memory cell is a last programmed word line according to a program order among word lines connected to the group of memory cells.

Abstract: A controller includes a processor suitable for performing a first erase operation on a target memory block; a tester suitable for performing a test operation to apply test voltages to selected points of word lines included in the target memory block; a counter suitable for counting the numbers of error memory cells sensed through the test voltages at the selected points; and a skipper suitable for setting test skip information based on the numbers of error memory cells.

Abstract: A controller includes a processor suitable for performing a first erase operation on a target memory block; a tester suitable for performing a test operation to apply test voltages to selected points of word lines included in the target memory block; a counter suitable for counting the numbers of error memory cells sensed through the test voltages at the selected points; and a skipper suitable for setting test skip information based on the numbers of error memory cells.

Abstract: A method for operating a data storage device using, as a storage medium, a nonvolatile memory device including a memory cell array which is constructed by pages including data cells and flag cells for storing whether upper bit (MSB) data is stored in a data cell, includes searching a last programmed page in the case where recovery is made from a power failure to a normal state; determining whether the last programmed page is an upper bit (MSB) page to be accessed to store upper bit (MSB) data; and adjusting a flag cell read voltage for reading flag cells, in the case where the last programmed page is an upper bit (MSB) page.