| 摘要 |
1509769 Data storage HONEYWELL INFORMATION SYSTEMS Inc 23 June 1975 [24 June 1974 (2)] 26521/75 Heading G4C Data formed of variable length data fields VALUE (A), VALUE (B), ... Fig. 3(B), is recorded on storage means, such as a magnetic tape, with a separator, #AB, #BC, ... between adjacent fields, each separator being the logical combination of the lengths of the respective two fields or the logical combination of codes which indicate the types of the respective two fields and which index a table containing the lengths of the fields. The logical combination may be the exclusive-OR combination, the difference or the ring sum. At each end of the data is a separator A which is the logical combination of zero and the length or code of the adjacent field VALUE (A). Certain of the separators, e.g. #AB may be formed of two parts #AO, #OB to allow insertion of padding at block boundaries. Data recorded in this way may be scanned in either direction; this may be used, for example, in text editing. The recorded data may be arranged as a plurality of fibres each including a plurality of records each including a plurality of groups each including a plurality of fields, each adjacent pair of files, records, groups and fields being separated by a separator (Fig. 7, not shown). A desired field may then be accessed by skipping over files, records and groups not containing the desired field. A search may also be made to locate a record containing a data field having a desired content by extracting the content of a specified field of each record and comparing the extracted content with the desired content. When a desired field is located the locations and lengths of the relevant file, record, group and field are retained so that subsequent files, records, groups or fields may be accessed. Data is tested for errors in the separators by generating, using the separators, the location of each separator and comparing each generated location with the known location of the end of the data. An error is detected if a generated location is beyond the known end or if the locations of all the separators have been generated and the known end has not been reached. If an error is detected the data is scanned from the other end and again the location of each separator is generated; the separator for which the same location is generated in both scans is the separator containing the error. |
