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The article presents information on various chapters of the Association for Computing Machinery (ACM) across the U.S. The Greater Rio Grande Chapter of ACM has recently extracted from its files a list of the titles of all technical papers presented at Chapter meetings since its inception in 1957. Using a program developed by D.K. Robbins of Sandia Corp., a KWIC-type listing of permuted titles of these papers has been made. This listing has been distributed to all members of the Chapter. Topics and speakers at ACM Chapters across the U.S. indicate the current trends of interest in computer science and data processing. The ACM Tidewater Chapter is sponsoring this spring a professional development course on "Real-Time Computing." The course is given by the Chapter's professional development chairman, Cecil Frost, who is applications staff specialist for Control Data Corp. At its April 21, 1966 meeting, the Westchester-Fairfield Chapter heard William Orchard-Hays speak on "Linear Programming of Computational Techniques."

As linear programming models grow bigger and bigger in size, much actual data that must be memorized is often put on magnetic tape or disk, and consequently there is an improportionately fast rise in the consumption of computer time. To cut down this expense, on ever increasing effort Is mode to design more efficient algorithms. This paper is meant to support the effort. If is attempted to find some characteristics of the way pivot column is found. The number of repetitions of a certain transfer of data from tape to core memory is considered. After some simplification, the problem is restated in a general way. The generating function of the probability distribution and the moment generating function of the number of repetitions is found. Asymptotic formulas are given for the moments using result from a paper of S. Narumi [1]. The results may be applied to write very efficient routines that search for an extreme value in a table. Formulas provide a means of calculating the computer timings in this case. [ABSTRACT FROM AUTHOR]

The use of the Kleene regular expression notation for describing algebraic language syntax, in particular of ALGOL is described in this paper. A FORTRAN II computer program for carrying out the elimination algorithm of Gorn, similar to Gaussian elimination for linear systems of algebraic equations, is described. This was applied to numerous smaller languages, including some sublanguages of ALGOL. A hand calculation result of the application of the algorithm to all of ALGOL is given, thus expressing the Revised ALGOL 1960 syntax in completely nonrecursive terms, as far as its context-free portion is concerned. This description in many ways is far more intuitively understood than the previous recursive description, it is suggested. The paper also includes results of the machine program, which does not include a simplification algorithm. [ABSTRACT FROM AUTHOR]

Sequencing to minimize mean finishing time (or mean time in system) is not only desirable to the user, but it also tends to minimize at each point in time the storage required to hold incomplete tasks. In this paper a deterministic model of independent tasks is introduced and new results are derived which extend and generalize the algorithms known for minimizing mean finishing time. In addition to presenting and analyzing new algorithms it is shown that the most general mean-finishing-time problem for independent tasks is polynomial complete, and hence unlikely to admit of a non-enumerative solution. [ABSTRACT FROM AUTHOR]

Virtual machine systems have been implemented on a limited number of third generation computer systems, e.g. CP-67 on the IBM 360/67. From previous empirical studies, it is known that certain third generation computer systems, e.g. the DEC PDP-10, cannot support a virtual machine system. In this paper, model of a third-generation-like computer system is developed. Formal techniques are used to derive precise sufficient conditions to test whether such an architecture can support virtual machines. [ABSTRACT FROM AUTHOR]

UNIX is a general-purpose, multi-user, interactive operating system for the Digital Equipment Corporation PDP-11/40 and 11/45 computers. It offers a number of features seldom found even in larger operating systems, including: (1) a hierarchical file system incorporating demountable volumes; (2) compatible file, device, and inter-process I/O; (3) the ability to initiate asynchronous processes; (4) system command language selectable on a per-user basis; and (5) over 100 subsystems including a dozen languages. This paper discusses the nature and implementation of the file system and of the user command interface. [ABSTRACT FROM AUTHOR]

The design of mechanisms to control the sharing of information in the Multics system is described. Five design principles help provide insight into the tradeoffs among different possible designs. The key mechanisms described include access control lists, hierarchical control of access specifications, identification and authentication of users, and primary memory protection. The paper ends with a discussion of several known weaknesses in the current protection mechanism design. [ABSTRACT FROM AUTHOR]

This paper describes the design philosophy of HYDRA —the kernel of an operating system for C.mmp, the Carnegie-Mellon Multi-Mini-Processor. This philosophy is realized through the introduction of a generalized notion of "resource," both physical and virtual, called an "object." Mechanisms are presented for dealing with objects, including the creation of new types, specification of new operations applicable to a given type, sharing, and protection of any reference to a given object against improper application of any of the operations defined with respect to that type of object. The mechanisms provide a coherent basis for extension of the system in two directions: the introduction of new facilities, and the creation of highly secure systems. [ABSTRACT FROM AUTHOR]

The paper describes a technique for compacting character sets in a digital computer while retaining fast access to individual bits. It considers the problem of minimizing the storage needed to contain such tables. Reduction techniques are developed, and the problem is shown to reduce to a covering problem. [ABSTRACT FROM AUTHOR]

Because of the large number of strategies and inference rules presently under consideration in automated theorem proving, there is a need for developing a language especially oriented toward automated theorem proving. This paper discusses some of the features and instructions of this language. The use of this language permits easy extension of automated theorem-proving programs to include new strategies and/or new inference rules. Such extendability will permit general experimentation with the various alternative systems. [ABSTRACT FROM AUTHOR]

Current methods for mechanical program verification require a complete predicate specification on each loop. Because this is tedious and error prone, producing a program with complete, correct predicates is reasonably difficult and would be facilitated by machine assistance. This paper discusses techniques for mechanically synthesizing loop predicates. Two classes of techniques are considered: (1) heuristic methods which derive loop predicates from boundary conditions and/or partially specified inductive assertions: (2) extraction methods which use input predicates and appropriate weak interpretations to obtain certain classes of loop predicates by an evaluation on the weak interpretation. [ABSTRACT FROM AUTHOR]

A data definition language is a declarative computer language for specifying data structures. Most data definition languages concentrate on the declaration of logical data structures with little concern for how these structures are physically realized on a computer system. However, the need for data definition languages which describe both the logical and physical aspects of data is increasingly apparent. Such languages will be a key element in the translation of data between computer systems, as well as in advanced data management systems and distributed data bases. This paper reviews past work in the data definition language for describing both logical and physical aspects of data. Applications of these "generalized" data definition languages are also discussed. [ABSTRACT FROM AUTHOR]

As part of an effort to design and implement a Fortran compiler on the ILLIAC IV, an extended Fortran, called IVTRAN, has been developed. This language provides a means of expressing data and control structures suitable for exploiting ILLIAC IV parallelism. This paper reviews the hardware characteristics of the nine and singles out unconventiona features which could be expected to influence langluage (and compiler) design. The implications of these features for data layout and algorithm structure are discussed, and the conclusion is drawn that data allocation rather than code structuring is the crucial ILLIAC optimization problem. A satisfactory method of data allocation is then presented. Language structures to utilize this storage method and express parallel algorithms are described. [ABSTRACT FROM AUTHOR]

Many control and access environment structures require that storage for a procedure activation exist at times when control is not nested within the procedure activated. This is straightforward to implement by dynamic storage allocation with linked blocks for each activation, but rather expensive in both time and space. This paper presents an implementation technique using a single stack to hold procedure activation storage which allows retention of that storage for durations not necessarily tied to control flow. The technique has the property that, in the simple case, it runs identically to the usual automatic stack allocation and deallocation procedure. Applications of this technique to multitasking, coroutines, backtracking, label-valued variables, and functional arguments are discussed. In the initial model, a single real processor is assumed, and the implementation assumes multiple-processes coordinate by passing control explicitly to one another. A multiprocessor implementation requires only a few changes to the basic technique, as described. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to the analysis of performance of the various key-to-address transformation methods. In this approach the keys in a file arc assumed to have been selected from the key space according to a certain probabilistic selection algorithm. All files with the same number of keys selected from this key space will be suitably weighted in accordance with the algorithm, and the average performance of the transformation methods on these files will be used as the potential of these methods. Using this analysis, methods with the same overall performance can be classified and key distributions partial to certain transformations can be identified. All this can be done analytically. The approach is applied to a group of transformation methods using files whose keys are selected randomly. [ABSTRACT FROM AUTHOR]

User-written programs on the Dartmouth Time-Sharing System can communicate with many remote terminals simultaneously and can control the interactions between these terminals. Such programs can be written using standard input and output instructions in any language available on the system. This paper describes how this multiple-terminal facility was implemented without requiring any changes in the system executive or in any of the system's compilers or interpreters. [ABSTRACT FROM AUTHOR]

The article offers information about activities related to the Association for Computing Machinery (ACM). According to Micro 6 program Chairman Louise H. Jones, research papers have been received for the microprogramming workshop sponsored by the Special Interest Group of ACM. The 8th Annual Urban Symposium of the ACM will take place in New York City which aims to deliver a discussion to individuals who uses computers to solve problems of urban society. The new executive director of the American Federation of Information Processing Societies Inc. is Robert W. Rector.

The article reports on finding all subgraphs of an undirected graph [H]. A maximal complete subgraph is also called clique which refers to a complete subgraph that is not included in any other complete subgraph. According to the authors, a research paper was released wherein descriptions of techniques to find maximal complete subgraphs are provided. The authors discussed two algorithms using a branch-and-bound technique so that there will be no clique. The first algorithm produces cliques in lexicographic order while the second is derived from the first algorithm.

This paper presents the goals and organization of a course about programming designed to provide entering students in a graduate program with a cultural enrichment in their professional lives. The students are expected to have taken at least two programming courses prior to this one and, therefore, to be familiar with at least two programming languages, both as students and users. Teaching someone how to program is similar to teaching him to play a musical instrument; neither skill can be taught—they must be learned. However, the teacher still serves several vital purposes: to present a set of rules for producing well-formed utterances; to offer numerous demonstrations of his own skill; and to function as an involved critic. Finally, the teacher is the source of information about the process in which the student is involved. [ABSTRACT FROM AUTHOR]

Mixtures of detection, avoidance, and prevention provide more effective and practical solutions to the deadlock problem than any one of these alone. The individual techniques can be tailored for subproblems of resource allocation and still operate together to prevent deadlocks. This paper presents a methods based on the concept of the hierarchical operating system, for constructing appropriate mixtures and suggests appropriate subsystems for the most frequently occurring resource allocation problems. [ABSTRACT FROM AUTHOR]

The HASP Execution Task Monitor periodically rearranges the OS/360 dispatching chain to give tasks preemptive execution priority in inverse order to that of their cpu utilization history. The effect is to keep the I/O bound tasks active and to prevent cpu bound tasks from locking out other tasks. This paper develops a simple model of the Execution Task Monitor and employs it to study the effectiveness of the monitor in improving system performance. A modified strategy for monitor control is investigated for the case of task execution in a memory heirarchy of varying speeds. [ABSTRACT FROM AUTHOR]

This paper describes LPARS, a locally-organized parsing system, designed for use in a continuous speech recognizer. LPARS processes a string of phonemes which contains ambiguity and error. The system is locally-organized in the sense that it builds local parse structures from reliable word candidates recognized anywhere in an input utterance. These local structures are used as "islands of reliability" to guide the search for more highly garbledwords which might complete the utterance. [ABSTRACT FROM AUTHOR]

Users of linear programming computer codes have realized the necessity of evaluating the capacity, effectiveness, and accuracy of the solutions provided by such codes. Large scale linear programming codes at most installations are assumed to be generating correct solutions without ever having been "benche-marked" by test problems with known solutions. The reason for this fail- ure to adequately test the codes is that rarely are there large problems with known solutions readily available. This paper presents a theoretical justification and an illustrative implementation of a method for generating linear programming test problems with known solutions. The method permits the generation of test problems that are of arbitrary size and have a wide range of numerical characteristics. [ABSTRACT FROM AUTHOR]

Programming systems which permit arbitrary linked list structures enable the user to create complicated structures without sufficient protection. Deletions can result in unreachable data elements, and there is no guarantee that additions will be performed properly. To remedy this situation, this paper proposes a Data Structure Description and Manipulation Language which provides for the creation of a restricted class of data structures but ensures the correctness of the program. This is accomplished by an explicit structure declaration facility, a restriction on the permissible operations, and execution-time checks. [ABSTRACT FROM AUTHOR]