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Communications of the ACM

Table of Contents


ACM President's Letter: The fourth estate — the computer revolution


An interactive display for approximation by linear programming

An interactive program with a graphical display has been developed for the approximation of data by means of a linear combination of functions (including splines) selected by the user. The coffiecients of the approximation are …

Multi-attribute retrieval with combined indexes

In this paper a file organization scheme designed to replace the use of the popular secondary index filing scheme (or inverted files on secondary key fields) is described. Through the use of redundancy and storing keys (or access …

A multiple-precision division algorithm

A generalized division algorithm for use with positive integral operands is presented. Depending upon the algebraic relationship of the first two ciphers of the divisor, one or at most two adjustments to the original divisor  …

NEATER2: a PL/I source statement reformatter

NEATER2 accepts a PL/I source program and operates on it to produce a reformatted version. When in the LOGICAL mode, NEATER2 indicates the logical structure of the source program in the indentation pattern of its output. Logic …

The linear quotient hash code

A new method of hash coding is presented and is shown to possess desirable attributes. Specifically, the algorithm is simple, efficient, and exhaustive, while needing little time per probe and using few probes per lookup. Performance …

A nonrecursive list compacting algorithm

A simple nonrecursive list structure compacting scheme or garbage collector suitable for both compact and LISP-like list structures is presented. The algorithm avoids the need for recursion by using the partial structure as it …

Recorded magnetic tape for information interchange (1600 CPI, phase encoded)

This proposed American National Standard has been accepted for publication by American National Standards Committee X3, Computers and Information Processing. In order that the final version of the proposed standard reflect the …

Unrecorded magnetic tape for information interchange (9 track—200 and 800 CPI, NRZI and 1600 CPI, P.E.)

This proposed American National Standard has been accepted for publication by American National Standards Committee X3, Computers and Information Processing. In order that the final version of the proposed standard reflect the …

Algorithms 401: an improved algorithm to produce complex primes


Algorithms 402: Increasing the efficiency of quicksort


Remark on algorithm 343: Eigenvalues and eigenvectors of a real general matrix


Remarks on algorithms 372: Algorithm 401: An algorithm to produce complex primes, csieve: an improved algorithm to produce complex primes


A generalized method for generating argument/function values

For any finite set of argument/function pairs, an algorithm can be automatically constructed which, on presentation of any argument, will generate its proper function value. Arguments are necessarily unique although functions …

Correction to “logical” arithmetric on computers with two's complement binary arithmetic

In reference [1] algorithms for performing arithmetic with unsigned two's complement operands were described. The scheme for division was implemented in a set of multiple-precision floating-point arithmetic routines [2]. User …

Comment on the working set model for program behavior

In the paper “The Working Set Model for Program Behavior” by Peter Denning [Comm. ACM 11, 5 (May 1968), 323-333], an algorithm is described for the management of a paged memory under demand paging. In the process of analyzing …

Condition numbers of Pei matrices