1. An operating method of a memory device which controls a nonvolatile memory, the operating method comprising: 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.