Communications of the ACM

Cellular arrays for the solution of graph problems

A cellular array is a two-dimensional, checkerboard type interconnection of identical modules (or cells), where each cell contains a few bits of memory and a small amount of combinational logic, and communicates mainly with its … K. N. Levitt, W. H. Kautz
Pages 789-801

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File organization: the consecutive retrieval property

The consecutive retrieval property is an important relation between a query set and record set. Its existence enables the design of an information retrieval system with a minimal search time and no redundant storage. Some important … Sakti P. Ghosh
Pages 802-808

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A new approach to automatic scanning of contour maps

The problem of automatic digitizing of contour maps is discussed. The structure of a general contour map is analyzed, and its topological properties are utilized in developing a new scanning algorithm. The problem of detection … M. Mor, T. Lamdan
Pages 809-812

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Automatic error analysis for determining precision

The problem considered is that of evaluating a rational expression to within any desired tolerance on a computer which performs variable-precision floating-point arithmetic operations. For example, the expression might be &pgr;/(&pgr; … Paul L. Richman
Pages 813-817

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Algorithm 431: A computer routine for quadratic and linear programming problems [H]

Arunachalam Ravindran
Pages 818-820

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Solution of the matrix equation AX + XB = C [F4]

R. H. Bartels, G. W. Stewart
Pages 820-826

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Thinning algorithms on rectangular, hexagonal, and triangular arrays

In this report three thinning algorithms are developed: one each for use with rectangular, hexagonal, and triangular arrays. The approach to the development of each algorithm is the same. Pictorial results produced by each of … E. S. Deutsch
Pages 827-837

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A comparison of floating point summation methods

In the June 1970 issue of Communications, Linz [1] proposed a method of pairwise summing of numbers to reduce accumulated roundoff error. Linz compared his method with only a simple recursive summation. The Linz method should … James Gregory
Page 838

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The eigenproblem of block tridiagonal matrices

Hatem M. Khalil
Page 839

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Comment on deadlock preventive method

D. L. Parnas, A. N. Habermann
Pages 840-841

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A controller for a braille terminal

Anderson and Rogers [1] have described a set of modifications which convert a standard model 33 tele-type into a device which produces embossed braille characters. Thus, blind computer users can communicate with a computer without … Richard Rubinstein, Julian Feldman
Pages 841-842

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On Foster's information storage and retrieval using AVL trees

Foster [2] has proposed a method of constructing an AVL tree with depth (height) h and the number of items N being fixed and with the weighted sum of the items a maximum. The purpose of this note is to show that this method does … K. C. Tan
Page 843

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ACM forum

Page 850

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ACM president's letter: the “A” in ACM is for association, not American

Anthony Ralston
Page 787

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