Practical work on data curation can usefully divided into two classes: efforts focused on the preservation of information at the bit or octet level (bit preservation) and efforts focused on higher levels. Efforts at both levels are essential to the successful preservation of digital materials; which area more urgently requires the attention and resources of data curators is an area of active controversy.
Briefly, bit preservation is the act of ensuring that devices in the future will be able to reproduce the sequence of bits, or octets, currently used to represent the information to be conserved. Bit preservation protects against bit rot and media failure, but not against other threats to digital preservation and access.
Information preservation is the act of ensuring that the information represented in a resource is preserved, possibly by translating it from an obsolescent format into a more current format. Note that format conversion protects against file-format obsolescence, but not against other possible threats to digital preservation.
Preservation of bits is a necessary part of digital preservation: since the bit sequence is the foundation for all the higher levels in the representation of the information, if the bit sequence is lost, the information will be lost as well. But bit preservation is not sufficient: a future user interested in a WordStar 1.3 document (for example) will be able to make use of the document effectively only if software capable of reading the WordStar 1.3 file format is available. Since WordStar was a very popular program for its day, such software may very possibly be available in practice. For the formats of less popular software, however, the situation looks less promising.