GB1482637A - Digital information storage arrangements - Google Patents

Abstract

1482637 Digital data storage NATIONAL RESEARCH DEVELOPMENT CORP 9 Dec 1974 [5 Oct 1973] 46595/73 Heading G4A] A digital information storage arrangement includes a data field 1 and an inverse field 3; to determine whether a word (e.g. "10") inserted by a key 5 is stored in data field 1, the word is used to address inverse field 3, the content ("1") of inverse field 3 at the addressed location indicating the address in data field 1 where the keyed-in word ("10") is stored. If the same word is notionally stored in more that one location of data field 1 a tag column (8, Fig. 2, not shown) may be associated with data field 1. The inverse field 3 stores the highest address of the word in data field 1; this location in data field 1, however, stores the next lower address in the data field 1 which notionally or actually stores that word and the tag is set to "1" to indicate this. The lowest address in such a chain actually stores that particular word and the tag is set to "0". In an alternative embodiment data field 1 stores words as in Fig. 1, inverse field 3 again stores the highest address of each word in data field 1 and the data field 1 is associated with a third, linkage, field (9, Fig. 3, not shown), at each location of which is stored. the next lower address in the chain of data field addresses storing that word. The chain of addresses and/or the stored word may be read out sequentially from the linkage field and/or data field. A fourth field may be included to indicate the number of entries of each word. The arrangement may use a plurality of data fields and associated inverse and linkage fields (Fig. 5, not shown), each word being split into bytes each of which is stored in a respective data field. Each byte of a keyed-in word is then fed to the respective inverse field, and a least value unit may be used to shorten the search-time for each multi-byte word. Two such arrangements may be used, with one least value unit, for sorting long words. To store long words using one such arrangement overflow bytes of a word may be written in the following address and these maybe associated with an "overflow" character.