G - Physics – 06 – F
Patent
G - Physics
06
F
354/244
G06F 3/06 (2006.01) G06F 13/04 (1980.01)
Patent
CA 1038500
SCAN AND READ CONTROL APPARATUS FOR A DISK STORAGE DRIVE IN A COMPUTER SYSTEM Abstract Control apparatus is provided for controlling a disk storage drive attachment in a computer system whereby records stored on the disk storage media are scanned and read within the same data field. The search key or search argument con- tained in main storage of the computer system is retrieved and compared with the key in the disk data field being scanned. The storage locations in the scan field not con- taining the search key are set to hexidecimal FF. The cen- tral processing unit (CPU) of the computer system is in a write to disk storage drive mode whereby the search argument is transferred from storage to the disk storage drive attach- ment as data is read from the disk storage drive. Decode apparatus senses the first hexidecimal FF from storage and switches the operation from a scan mode into a read mode and if a scan low or equal condition resulted from the com- parison, the disk data field is read into the storage scan field with one byte of FF between the search key in storage and the newly stored disk data. The one byte of FF still provides an indication of the end of the search key. The operation then switches back to the scan mode and repeats in the manner described, i.e., sequential disk data fields are read into the storage scan field, until a comparison of equal or high results. When a high condition exists, a latch is set to block the storage of disk data in main storage because the storage scan field now contains the disk data field which had been sought, i.e., the one con- taining the desired index key.
209551
Lewis David O.
Miller Thomas H.
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