associative memory

a storage unit of digital computers in which selection (entry) is performed not according to concrete address but rather according to a preset combination (association) of attributes characteristic of the desired information. Such attributes can be part of a word (number), attached to it for detection among other words, certain features of the word itself (for example, the presence of specific codes in its digits), the absolute value of a word, its presence in a preset range, and so on.

The operation of an associative memory is based on the representation of all information in the form of a sequence of zones according to properties and characteristic attributes. In this case the retrieval of information is reduced to the determination of the zone according to the preset attributes by means of scanning and comparison of those attributes with the attributes that are stored in the associative memory. There are two basic methods of realizing the associative memory. The first is the construction of a memory with storage cells that have the capability of performing simultaneously the functions of storage, nondestructive reading, and comparison. Such a method of realizing an associative memory is called network parallel-associative—that is, the required sets of attributes are preserved in all the memory cells, and the information that possesses a given set of attributes is searched for simultaneously and independently over the entire storage capacity. Card indexes for edge-punched cards are prototypes of such an associative memory. Thin-film kryotrons, transfluxors, biaxes, magnetic thin films, and so on are used as storage elements of network-realized associative memories.

The second method of realizing an associative memory is the programmed organization (modeling) of the memory. It consists of the establishment of associative connections between the information contained in the memory by means of ordered arrangement of the information in the form of sequential chains or groups (lists) connected by linkage addresses whose codes are stored in the same memory cells. This procedure is the more suitable for practical realization in dealing with large volumes of information because it provides for the use of conventional accumulators with address reference.

The use of an associative memory considerably facilitates the programming and solution of informational-logical problems and accelerates by hundreds (thousands) of times the speed of retrieval, analysis, classification, and processing of data.