MEMORY CONTROLLER, MEMORY SYSTEM AND OPERATING METHOD OF MEMORY DEVICE

A memory controller includes a block ratio calculator configured to calculate a ratio of free blocks among memory blocks for storing data; a policy selector configured to select, based on the calculated ratio of free blocks, any one garbage collection policy of a first garbage collection policy of specifying priorities to be used to select a victim block depending on attributes of the data, and a second garbage collection policy of specifying the priorities to be used to select the victim block regardless of the attributes of the data; and a garbage collection performing component configured to perform a garbage collection operation on at least one memory block of the memory blocks according to the garbage collection policy selected by the policy selector.