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This paper presents the design and implementation of special hardware for effective use of the method of superimposed codes. It is shown that the method of superimposed codes is particularly well suited to easy design and implementation of fast and modular hardware. The implementation has shown that a performance gain of two orders of magnitude over conventional software implementations is obtained by using the special hardware. This makes the method of superimposed codes extremely attractive for data base system requiring partial match retrieval. We also demonstrate that the associative memory design is easily adaptable to large scale integration which would make such an approach very cost effective and lead to even further gains in performance.

In this paper we describe the design, testing, and use of drand48—a good, pseudo‐random number generator based upon the linear congruential algorithm and 48‐bit integer arithmetic. The drand48 subroutine is callable from C‐language programs and is available in the subroutine library of the UNIX* operating system. Versions coded in assembly language now exist for both the PDP‐11 and VAX‐11 computers; a version coded in a “portable” dialect of C language has been produced by Rosier for the Western Electric 3B20 and other machines. Given the same initialization value, all these versions produce the identical sequence of pseudo‐random numbers. Versions of drand48 in the assembly language of other computers or for other programming languages clearly could be implemented, and some output results have been tabulated to aid in testing and debugging such newly coded subroutines. Timing results for drand48 on the PDP‐11/45, the PDP‐11/70, the VAX‐11/750, and the VAX‐11/780 are also presented and compared.