A pair of attribute and data is stored in each word memory of associative memories. A retrieval is performed using reference data applied from an exterior and the pair of attribute and data stored in each word memory of associative memories. Upon receipt of a match of the attribute, a signal representing a match or mismatch of both attribute and data except the attribute is supplied to a data line. At the time of subsequent retrieval, upon receipt of a match of the attribute, data appearing on the data line is taken in.

A block oriented random access memory (BORAM) is disclosed as comprising a plurality of memory arrays of metal-nitride-oxide semiconductor (MNOS) memory elements. Each memory array includes a plurality of the MNOS memory elements disposed in rows and columns, and serial or sequential means such as a shift register for writing and reading data to and from the memory elements through column conductors associated with each column of the memory elements. A temporary storage means such as a latch is inserted between each stage of the shift register and the column conductor, whereby a multiplexing function can be performed between the stage outputs of the shift register and the columns of the memory elements. Address means is provided for the rows of memory elements, whereby a row may be selected for entry of data through its associated column conductor. In one illustrative embodiment, a plurality of such assemblies is assembled into a block capable of being separately addressed, wherein each such assembly is capable of storing one bit of a multi-bit word of data. In turn, a plurality of such blocks is assembled to form the block oriented random access memory, wherein each such block may be randomly accessed, and the data therein sequentially read and written.

A content addressable memory consists of a plurality of memory units each of which may be an integrated circuit. Each unit receives an input group of digits forming all or part of an input key code, and compares it simultaneously with a plurality of equally sized groups of digits stored in the memory of the unit. The memory of a unit has 32K bytes of storage elements functionally arranged in 512 rows and column. The 64 bytes forming a row are each compared with an input group of 8 binary digits. A status bit is produced for each of the 64 bytes of a row and indicates whether or not the input group matches the particular byte. The match need not be perfect and certain digits may be masked so that comparison of them does not detract from the match assessment. The status bits are combined logically to produce higher and higher order status bits selectively indicating the presence of a match in larger and larger groups of storage elements up to the entire memory of the unit. The single highest level status bit from each unit is combined logically with similar bits from other units to produce even higher order status bits. The status bits are stored so that the addresses of groups matching the input group can be discovered from then. For an input key code having several input groups of digits, the input groups are applied sequentially to the units. The units also produce a "just one" output when only a single match to an input group is found. The "just one" outputs are combined logically to produce a hierarchy of "just one" outputs similar to that of the status bits. For a multi-input group key code, the "just one" output can be used to terminate the search before all input groups have been searched for.

A content addressable memory consists of a plurality of memory units each of which may be an integrated circuit. Each unit receives an input group of digits forming all or part of an input key code, and compares it simultaneously with a plurality of equally sized groups of digits stored in the memory of the unit. The memory of a unit has 32K bytes of storage elements functionally arranged in 512 rows and column. The 64 bytes forming a row are each compared with an input group of 8 binary digits. A status bit is produced for each of the 64 bytes of a row and indicates whether or not the input group matches the particular byte. The match need not be perfect and certain digits may be masked so that comparison of them does not detract from the match assessment. The status bits are combined logically to produce higher and higher order status bits selectively indicating the presence of a match in larger and larger groups of storage elements up to the entire memory of the unit. The single highest level status bit from each unit is combined logically with similar bits from other units to produce even higher order status bits. The status bits are stored so that the addresses of groups matching the input group can be discovered from them. For an input key code having several input groups of digits, the input groups are applied sequentially to the units. The units also produce a "just one" output when only a single match to an input group is found. The "just one" outputs are combined logically to produce a hierarchy of "just one" outputs similar to that of the status bits. For a multi-input group key code, the "just one" output can be used to terminate the search before all input groups have been searched for.

Apparatus for storing and associatively manipulating a large (10 .times. 10.sup.6 character) data base is disclosed. Said apparatus providing access control to devices constructed to operate in a block oriented random access manner and providing decision logic asynchronous to a digital computer connected to said apparatus to provide the location of stored data satisfying selected Boolean combinations of conditions and conjunctive operations over a designated portion of the total data base.