Nonvolatile memory device, operating method thereof, and memory system including the same

A nonvolatile memory device includes a memory cell array and a control unit. The memory cell array includes a plurality of memory regions coupled to a plurality of word lines. The plurality of memory regions include first and second memory regions coupled to upper and lower word lines, respectively. The control logic performs, after receiving first data and second data, a first program operation on the first memory region to store the first data and a second program operation on the second memory region to store the second data.