An operating method is for a memory device which controls a nonvolatile memory. The operating method includes managing a program depth bit map indicating an upper page program state of each of a plurality of word lines of the nonvolatile memory in response to an external write request, and outputting one of a plurality of different read commands to the nonvolatile memory based on information of the program depth bit map corresponding to a word line to be accessed in response to an external read request.