Patent GB-1004762-A (GB)
Title: Method for optional writing-in and reading-out of information with variable word length in circulating memories
IPC: G06F5/08
Filed: 1962-10-24
Abstract: 1,004,762. Data storage. STANDARD TELEPHONES & CABLES Ltd. Oct. 24, 1962 [Oct. 21, 1961], No. 40203/62. Drawings to Specification. Heading G4C. A buffer store receives and transmits data character-by-character relative to input-output devices and in block form relative to a data processor and comprises a circulatory store having a data track with a single read-write head, the data character locations on the track being regarded as belonging alternately to two different groups, the information transfer being controlled by control bits associated with each character location, which bits may be altered on a basis dependent on the group to which the corresponding storage locations belong. The arrangement may be applied to an airline seat reservation system. As described, each storage location comprises two control bit positions and five data character positions for storing data in teleprinter code, the locations belonging alternately to one of two groups, group A and group B. First method.-(1) Transfer from input device to buffer store. Initially, the whole track contains " O "s apart from the control bits of the first storage location (which belongs to group A), which are " 1, 1." Writing a character requires two drum revolutions in the first of which the sensing of the first " 1 " in the pair of control bits initiates the writing of the character to be stored in the first storage location together with " 1, 1 " in the control bit positions of the second storage location, which belongs to group B. In the second drum revolution " 0, 0 " is is written in the control bit positions of all the locations in the group to which the location utilized belongs, in this case group A. Further characters are written in a similar way. (2) transfer from processor to buffer store. The initial track condition is as in (1), but the sensing of the first control bit " 1 " causes writing of the whole block of characters to be transferred, with " 0, 0 " in the intermediate control bit positions, and " 1, 1 " in the control bit positions following the last character entered. The last character may be a " dummy " to ensure that the total number of characters in the block to be transferred is odd. In the second drum revolution a " 0 " is written in the first control bit position of all locations of group A. Thus, the start of the stored block is indicated by " 0, 1 " and the first subsequent vacant position by " 1, 1." (3) Transfer from buffer store to output device. Read-out commences when the first control bit pair with a " 1 " in the second position is sensed. The corresponding character is read and a " 1 " written in the second control bit position of the succeeding location. In the second drum revolution " 0 " is written in all control bit positions of the group to which the read character belongs. Subsequent characters are read out similarly. (4) Transfer from buffer store to processor. Starting from the first storage location, all data is read until a storage location having a " 1 " in the first control bit position is sensed. Second method.-This is generally similar to the first method, but the control bits are employed differently. For example, in the initial state all control bits are zero and for characterby-character transfer from the input device, each stored character is marked by a " 1 " in the first control bit position. Circuit details.-Circuits employing gates, flip-flops and delays are described for carrying out both methods (Figs. 1-6, not shown).