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Communications of the ACM

Table of Contents


ACM President's Letter: again, Shcharansky


Self-assessment procedure IV


Computer science faculties: the current status of minorities and women

The results of a survey conducted in the fall of 1975 to determine the status of women and minority faculty members in academic computer science are presented. Faculty members were compared with respect to professional background …

A method for obtaining digital signatures and public-key cryptosystems

An encryption method is presented with the novel property that publicly revealing an encryption key does not thereby reveal the corresponding decryption key. This has two important consequences: (1) Couriers or other secure means …

Systematic recursion removal

The recursion removal algorithm presented by Strong and Walker is amplified and applied to a relatively complex PL/I program. The aim is to demonstrate systematic recursion-removal techniques on something more complex than Knuth's …

Covering edges by cliques with regard to keyword conflicts and intersection graphs

Kellerman has presented a method for determining keyword conflicts and described a heuristic algorithm which solves a certain combinatorial optimization problem in connection with this method. This optimization problem is here …

B-trees re-examined

The B-tree and its variants have, with increasing frequency, been proposed as a basic storage structure for multiuser database applications. Here, three potential problems which must be dealt with in such a structure that do  …

A comparison of numerical techniques in Markov modeling

This paper presents several numerical methods which may be used to obtain the stationary probability vectors of Markovian models. An example of a nearly decomposable system is considered, and the results obtained by the different …

Relaxation methods for image reconstruction

The problem of recovering an image (a function of two variables) from experimentally available integrals of its grayness over thin strips is of great importance in a large number of scientific areas. An important version of the …

Is “sometime” sometimes better than “always”?: intermittent assertions in proving program correctness

This paper explores a technique for proving the correctness and termination of programs simultaneously. This approach, the intermittent-assertion method, involves documenting the program with assertions that must be true at some …

Some new methods of detecting step edges in digital pictures

This note describes two operators that respond to step edges, but not to ramps. The first is similar to the digital Laplacian, but uses the max, rather than the sum, of the x and y second differences. The second uses the difference …

ACM forum: on the Non cooperation Motion