A method of operating a memory device is provided. The memory device includes a plurality of multi-level memory cells of which each memory cell includes L levels. Data which is expressed in a binary number is received. A P-length string is generated from the data. The P-length string is converted to a Q-length string. The Q-length string is distributed using I levels by eliminating at least one level from the L levels. P and Q represent binary bit lengths of the P-length string and the Q-length string. Q is greater than P. L represents a maximum number of levels which each multi-level memory cell has. I is smaller than L. The Q-length string is programmed into the plurality of memory cells.