System for retrieving token having a selected nest level and satisfying

Abstract

In a token train retrieval device including a memory device (24) for memorizing a plurality of tokens as stored tokens each of which starts at a starting address and ends at an end address and each of which has a nest level selected from first through N-th nest levels and comprises a header and a data set where the header comprises a data length code and a data identifier code including a nest bit, a retrieval condition memory (25) memorizes a retrieval condition as a stored condition. Supplied with the header, a header register (26) holds the data length code, the data identifier code, and the nest bit as a held data length code, a held data identifier code, and a held nest bit. Responsive to the held data identifier code and a decided nest level, a checking circuit (27) checks whether or not the stored condition is satisfied to produce a matching signal when the stored condition is satisfied. An intra-train address generating circuit (29) generates an intra-train address variable in response to the matching signal, the held nest bit, and the held data length code. By using the intra-train address and the held data length code, an end address calculating circuit (30) calculates the end address of each token as a calculated address. By using the calculated address, the intra-train addresses, and the held nest bit, a nest level decision circuit (31) decides the decided nest level indicative of one of the first through the N-th nest levels.