NAND multi-level cell flash memories are
widely used due to their low cost, portability and high capacity as
storage devices. However, large program/erasure cycles of flash
memory incur reliability problems. WOM (write once memory)
codes are the techniques that allow information to be written
in a cell multiple times without erasure. However, conventional
error correction codes cannot be used directly for WOM encoded
codes. A key contribution of this paper is that we propose
bidirectional limited magnitude error correction schemes for nonbinary
WOM codes. The proposed codes are systematic, flexible
and based on the distinct sum sets and modulo operation.