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Communications of the ACM

Table of Contents

ACM President's Letter

Automatic segmentation of cyclic program structures based on connectivity and processor timing

Time-shared, multiprogrammed, and overlayed batch systems frequently require segmentation of computer programs into discrete portions. These program portions are transferred between executable and peripheral storage whenever  …

Recursive computation of certain derivatives&a study of error propagation

A brief study is made of the propagation of errors in linear first-order difference equations. The recursive computation of successive derivatives of ex/x and (cos x)/x is considered as an llustration.

A processor allocation method for time-sharing

A scheduling algorithm is proposed which is intended to minimize changes of tasks on processors and thereby reduce overhead. The algorithm also has application to more general resource allocation problems. It is implemented by …

Natural language question-answering systems: 1969

Recent experiments in programming natural language question-answering systems are reviewed to summarize the methods that have been developed for syntactic, semantic, and logical analysis of English strings. It is concluded that …

Experience with an extensible language

An operational extensible language system is described. The system and its base language are appraised with respect to efficiency, flexibility, and utility for different categories of users.

A note on minimal length polygonal approximation to a digitized contour

A method for extracting a smooth polygonal contour from a digitized image is illustrated. The ordered sequence of contour points and the connection graph of the image are first obtained by a modified Ledley algorithm in one image …

Algorithm 368: Numerical inversion of Laplace transforms [D5]

Algorithm 369: Generator of random numbers satisfying the Poisson distribution [G5]

General random number generator [G5]

Algorithm 372: An algorithm to produce complex primes, CSIEVE [A1]

Algorithm 371: Partitions in natural order [A1]

Remark on algorithm 282 [S22] derivatives of ex/x, cos(x)/x, and sin (x)/x

Remark on algorithm 347 [M1]: an efficient algorithm for sorting with minimal storage

Representation for calendar date for machine-to-machine data interchange

Interchange rolls of perforated tape for information interchange

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

Fortran Tausworthe pseudorandom number generator

Intermediate computations in an “Extremely Portable Random Number Generator” by J. B. Kruskal [Comm. ACM 12, 2 (Feb. 1969), 93-94] exceed 15 bits plus sign. This is a severe limitation since the majority of small computers uses …