A data storage device includes a nonvolatile memory device, a storage controller and a mapping controller. The nonvolatile memory device stores an execution code that controls operations of the data storage device. The storage controller uploads and stores the execution code from the nonvolatile memory device to a host memory buffer included in an external host device, and downloads the execution code in realtime from the host memory buffer to execute the execution code that is downloaded from the host memory buffer. The mapping controller manages a mapping table including mapping relations between the execution code and host addresses of the host memory buffer at which the execution code is stored. A speed of accessing the execution code is increased and performance of the data storage device is enhanced by using the host memory buffer as storage of the execution code to control the operation of the data storage device.