Error and loss correction in a data base stored on a two dimensional

Abstract

A digital data base 10 having record data codes representing an initial digital record is printed at predetermined code sites 12 within two dimensional code storage area 14 on the surface of on base medium 10B. The digital data base includes redundant check codes and one or more redundant check-check codes for permitting data error and data loss correction. The two dimensional code storage area has a coordinate system for defining code positions therein. The code sites are physically positioned within the code storage area at predetermined coordinates. A plurality of error checking sets are formed by the code sites, each containing one or more data codes and one or more check codes. The bits in the check codes in each error checking set are determined by the bits in the data codes of the same error checking set, and are in error correcting relationship therewith. Each data code and each check code are included in 'L' error checking sets to provide 'L' levels of inter-locking error checking and correcting. In addition, a of plurality error checking-checking sets are also formed by the code sites. Each error checking-checking set contains one or more check codes and one or more check-check codes in error correcting relationship therewith. Each check code and each check-check code are also included in 'L' error checking-checking.