GB1247006A - Improvements in or relating to the indexing and retrieval of information - Google Patents

Abstract

1,247,006. Indexing and retrieving information. DEFENCE; SECRETARY OF STATE FOR. 27 June, 1969 [29 March, 1968], No. 15210/68. Heading G4A. In a computer, letters of a keyword relating to a given item of information are converted to binary numbers, the numbers being combined to give a secondary binary number representing the word which is stored in a quick access store. This process is repeated for each keyword in the item of information, and then all the stored secondary numbers are combined to give a 32-bit composite keyword which is stored in a slow access store, e.g. magnetic tape, drum or disc at the address corresponding to an identifying symbol of the information. Each 32-bit word is converted into a four-bit number by dividing the 32-bits into four groups of eight, each group resulting in a "1" bit if there is at least one "1" in the digit of the group and a "0" bit otherwise. These four bit numbers may be transferred to the slow access store with the address of the corresponding 32-bit word. Alternatively, part of the slow access store may be designated for each four-bit word. In a further modification the 32-bit word is fed to the quick access store, a further number is derived from it, the number determining the part of the four access store to which the keyword is transferred. To retrieve information a list of keywords is fed in to form a first 32-bit composite word and from it a third word to indicate in which part of the store a possible match can exist. The read in composite keyword (held in the quick access store) is compared with the stored composite keywords (in the indicated part of the slow access store) and the computer prints out the data corresponding to matching composite keywords. In the embodiment described in which the input may be in the form of punched paper tape the letters of the keyword are converted to the binary representation of their position in the alphabet, that is A becomes 0001. These numbers are then added without carry to give a further four-digit number having a decimal value between 0 and 31 and the composite keyword is formed by putting a "1" in a 32- bit digit at the position corresponding to its decimal value.