1. An operating method of a data storage device including a non-volatile memory device which includes a memory cell array; and a memory controller which includes a buffer memory and which controls the non-volatile memory device, the operating method comprising: storing data in the buffer memory according to an external request; determining whether the data stored in the buffer memory is data accompanying a buffer program operation of the memory cell array; when the data stored in the buffer memory is data accompanying the buffer program operation, determining whether a main program operation on the memory cell array is required; when a main program operation on the memory cell array is required, determining a program pattern of the main program operation on the memory cell array; and issuing a set of commands for the main program operation on the memory cell array to the multi-bit memory device, based on the determined program pattern.