Location of faults on magnetic memory disc tracks - using preformed sequence to locate track faults and recording faulty track data in index at head of each data block

摘要

Faults on magnetic discs which are used for bulk storage in computer applications are located in a 'pre-formatting' procedure and data on their location is recorded on the disc to prevent errors during use of the disc. Faster and fuller useage of the disc space is obtained by placing an index at the beginning of each data block giving start locations of faulty tracks, along with an identifier for the track, a separator, the position of faults, a key zone and a data zone indicating whether the fault lies in a track separation interval or in a data field, and also the length of the data field immediately preceding the fault. The identification zone is composed of three groups of bytes, including the information relating to the localisation of faults in that zone, an address, an 8 bit flag, a byte indicating the length of the key zone and a byte giving the length of the data field, together with a self-correcting code.