| 摘要 |
968, 856. Magnetic digital-data-storage apparatus. RADIO CORPORATION OF AMERICA. Dec. 14, 1960 [Jan. 11,1960], No. 43114/60. Heading G4C. Apparatus for searching a data file for all messages stored therein having in a predetermined message portion, predetermined common message characters comprises means for comparing, character by character, characters received from the data file and from a criterion register storing the desired common characters together with masking characters, the comparing means producing an output if the compared characters are equal, means being provided to produce the equality output signal in response to each of the masking characters. As described, a data file comprises a series of messages such as those shown in Fig. 3, each message including a plurality of items separated by characters ISS, each item comprising a number of characters composed of six binary bits in parallel. The data file is stored on a magnetic tape or drum 14, Fig. 1B, and the criterion to be searched for is stored in circulatory shift registers 67, Fig. 1A, a typical criterion being shown in Fig. 4, as a series of characters such as Y, 7, 3 and masking characters CS, all data messages in which a predetermined item has the chosen characters Y, Z, 3 in the same positions as in the criterion being selected from the data file. In operation, the desired criterion is fed into the shift registers 67 from an input 86 under the control of a signal CI from a control unit 20. The characters in the file stored at 14 are read out successively into a register 30, Fig. 1B, adapted to store one character. A selector device 36 initiates the comparison operation for each file message when the required predetermined portion of the message is reached, the device 36 setting a flip-flop 56 to provide a "comparison allowable" signal CAFF(1). When the first criterion digit reaches the output of the registers 67, an "and" gate 64, Fig. 1A, is closed to prevent further shift and the output of the registers 67 is fed over a line 91 where it is recognized in circuits 90,92 as a masking character CS or an end of criterion character EC respectively or is compared in a comparator 44 (Fig. 2, not-shown) with the file register character in the register 30. As described, the first criterion character is a masking character CS so that the circuit 90 sets a flip-flop 102 which is reset at the beginning of the next character comparison. The setting of the flip-flop 102 removes an input to an "and" gate 104 thereby preventing a flip-flop 106 from being set. The next characters are compared in the comparator 44, and since they are identical an output from the comparator again sets the flip-flop 102. In this way, the whole criterion is compared, comparison being terminated upon the next recognition of a separating symbol ISS in a circuit 42, Fig. 1B. If the message shown in Fig. 3A is being compared, flip-flop 106 is never set and at the end of the comparison, a "valid compare" output signal is obtained from a gate 108. If the comparator 44 had found any pair of characters to be unequal the flipflop 106 would have been set and no final output would have been obtained at the gate 108. If the end of criterion symbol EC, Fig. 4, is read before the next separating symbol ISS, it is recognised in circuit 92 thereby setting an "override" flip-flop 98 to produce the equivalent of a successful character comparison whatever the subsequent file characters until the next separation symbol ISS terminates the comparison. Messages such as Fig. 3B will therefore also give a "valid compare" output. If there were no end of criterion symbol EC, as in Figs. 5, 6 (not shown), a "valid compare" output could only be produced by a file portion having precisely the same number of characters as the criterion. The "valid compare"output may be employed to control the read out of the selectted message from the file stored at 14. Specification 792,965 is referred to.
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