Correcting faults in write-once memory

We consider codes for write-once memory in tile presence of stuck-at-0 and stueb-at-1 faults. Such fault- Tolerant codes generally require less redundancy than error-correcting codes, as faults detected during the writing process can affect subsequent behavior of that process. We present pointer codes, which use part of a codeword to point to faults in other parts of the codeword. A pointer code can encode n-bit messages in the presence of f faults with only f(log2n + o(1)) redundancy. We derive a lower bound on the redundancy of such a fault-tolerant code of slightly less than f log n. We also examine some models where all stuck-at information is known in advance, and analyze the expected redundancy of pointer codes.