Guided Blocks WOM codes

A binary Write Once Memory (WOM) device is a storage mechanism in which a 0-bit can be overwritten much more easily than a 1-bit. A famous example is the flash memory technology, where 0→1 transitions are allowed, but 1 → 0 transitions require a costly erase procedure and are therefore prohibited. A WOM code is a coding scheme that permits multiple writes to the WOM without violating the WOM rule. The properties of WOM attracted attention even before flash memory was invented. Rivest and Shamir [2] proposed an elegant WOM code that uses 3 bits to write two rounds of any combination of 2 bits. As alternative, context sensitive rewriting codes have been considered [1], in which the new information stored in the second round utilizes certain portions of the output of the first round for unambiguous reuse. Some of these encodings are based on Fibonacci Codes, whose primary relevant property is that they contain no adjacent 1-bits, except as suffixes of all of their codewords.