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The article focuses on DigitalDesk, which is a real physical desk where one can stack papers, lay out their favorite pencils and markers, and leave coffee cup, but it is enhanced to provide some characteristics of an electronic workstation. A computer display is projected onto the desk, and video cameras pointed down at the desk feed an image-processing system that can sense what the user is doing. Three important characteristics of DigitalDesk are, it projects electronic images down onto the desk and onto paper documents, it responds to interaction with pens or bare fingers and it can read paper documents placed on the desk. The DigitalDesk provides a computer-augmented environment in which paper gains electronic properties that allow it to overcome some of its physical limitations. The calculator is a simple and familiar application that can benefit from the DigitalDesk. It allows people to place ordinary paper documents on the desk and simply point at a printed number to enter it into the calculator.

The effective operation of free enterprise in creating the envisioned information service industry is dependent upon three accomplishments: (1) the restructuring of our information processing industry so that a clear division of costs is mode among computing, communications, and the development of information services; (2) the wide use of multiaccess system concepts so that information services may share in the use of computer installations and so that the cost of their construction is reasonable; and (3) the development of public, message-switched communications services so that adequate provisions are made for Information security. [ABSTRACT FROM AUTHOR]

In this paper, we study the problem of estimating the state of a switched linear system (SLS), when the observation of the system is subject to communication constraints. We introduce the concept of worst-case topological entropy of such systems, and we show that this quantity is equal to the minimal data rate (number of bits per second) required for the state estimation of the system under arbitrary switching. Furthermore, we provide a closed-form expression for the worst-case topological entropy of switched linear systems, showing that its evaluation reduces to the computation of the joint spectral radius (JSR) of some lifted switched linear system obtained from the original one by using tools from multilinear algebra, and thus can benefit from well-established algorithms for the stability analysis of switched linear systems. Finally, drawing on this expression, we describe a practical coder-decoder that estimates the state of the system and operates at a data rate arbitrarily close to the worst-case topological entropy. [ABSTRACT FROM AUTHOR]

Monitoring and troubleshooting distributed systems are notoriously difficult; potential problems are complex, varied, and unpredictable. The monitoring and diagnosis tools commonly used today—logs, counters, and metrics—have two important limitations: what gets recorded is defined a priori, and the information is recorded in a component- or machine-centric way, making it extremely hard to correlate events that cross these boundaries. This paper presents Pivot Tracing, a monitoring framework for distributed systems that addresses both limitations by combining dynamic instrumentation with a novel relational operator: the happened-before join. Pivot Tracing gives users, at runtime, the ability to define arbitrary metrics at one point of the system, while being able to select, filter, and group by events meaningful at other parts of the system, even when crossing component or machine boundaries. Pivot Tracing does not correlate cross-component events using expensive global aggregations, nor does it perform offline analysis. Instead, Pivot Tracing directly correlates events as they happen by piggybacking metadata alongside requests as they execute. This gives Pivot Tracing low runtime overhead—less than 1% for many cross-component monitoring queries. [ABSTRACT FROM AUTHOR]

The article presents information on the proposed American Standard, "Eleven-Sixteenths Inch Perforated Paper Tape." This standard covers the physical dimensions of the paper tape and its perforations. This standard is for perforated paper tape with fully punched round holes. The punched tape shall have an overall width of 0.686 inch plus or minus 0.003 inch after the tape has been conditioned to within 69.5 degrees F to 76.5 degrees F and 48 percent to 52 percent relative humidity for a period of 24 hours. The tape shall be used for recording up to five levels of information across the tape. The feed holes in the tape shall be fully punched and round with a diameter of 0.046 inch plus 0.002 minus 0.001 inch. All holes punched in the tape shall nominally center on the true intersection of longitudinal and perpendicular transverse center lines spaced 0.100 inch apart. Tolerances on locations of code holes in any one transverse row, relative to the center lines of the feed hole in that row, shall be plus or minus 0.002 inch in the transverse direction and plus or minus 0.003 inch in the longitudinal direction.

Invites several research papers for the forthcoming conferences related to the computing systems.

Errors in dynamic random access memory (DRAM) are a common form of hardware failure in modern compute clusters. Failures are costly both in terms of hardware replacement costs and service disruption. While a large body of work exists on DRAM in laboratory conditions, little has been reported on real DRAM failures in large production clusters. In this paper, we analyze measurements of memory errors in a large fleet of commodity servers over a period of 2.5 years. The collected data covers multiple vendors, DRAM capacities and technologies, and comprises many millions of dual in-line memory module (DIMM) days. The goal of this paper is to answer questions such as the following: How common are memory errors in practice? What are their statistical properties? How are they affected by external factors, such as temperature and utilization, and by chipspecific factors, such as chip density, memory technology, and DIMM age? We find that DRAM error behavior in the field differs in many key aspects from commonly held assumptions. For example, we observe DRAM error rates that are orders of magnitude higher than previously reported, with 25,000- 70,000 errors per billion device hours per Mb and more than 8% of DIMMs affected by errors per year. We provide strong evidence that memory errors are dominated by hard errors, rather than soft errors, which previous work suspects to be the dominant error mode. We find that temperature, known to strongly impact DIMM error rates in lab conditions, has a surprisingly small effect on error behavior in the field, when taking all other factors into account. Finally, unlike commonly feared, we do not observe any indication that newer generations of DIMMs have worse error behavior. [ABSTRACT FROM AUTHOR]

In this paper an axiomatic, fundamental metamodel of data flow is constructed. The components of the metamodel are the states along the flow of data: physical events, language (data), stored data, human data processing, and decision making. Transfers front one state to another are performed by functions: coding, keying, processing, perception, and human acting. The entire flow is evaluated by a value function. Each of the states and functions is rigorously described by means of definitions, axioms, and theorems. The main purpose of the meta model is to provide a common framework for various models in MIS and consequently to remedy the "Tower of Babel" syndrome prevailing in this area. The way the metamodel can he used to develop other models in MIS is explained in the last part of the paper. [ABSTRACT FROM AUTHOR]

This paper discusses a family of algorithms for computing the volume, moments of inertia, and other integral properties of geometrically complex solids, e.g. typical mechanical parts. The algorithms produce approximate decompositions of solids into cuboid cells whose integral properties are easy to compute. The paper focuses on versions of the algorithms which operate on solids represented by Constructive Solid Geometry (CSG), i.e., as set-theoretical combinations of primitive solid "building blocks." Two known algorithms are summarized and a new algorithm is presented. The efficiencies and accuracies of the three algorithms are analyzed theoretically and compared experimentally. The new algorithm uses recursive subdivision to convert CSG representations of complex solids into approximate cellular decompositions based on variably sized blocks. Experimental data show that the new algorithm is efficient and has predictable accuracy. It also has other potential applications, e.g., in producing approximate octree representations of complex solids and in robot navigation. [ABSTRACT FROM AUTHOR]

Analytical results, related to the availability of a computer system constructed of unreliable processors, are presented in this paper. These results are obtained by using various computer-aided algebraic manipulation techniques. A major purpose of this paper is to demonstrate that the difficulties of obtaining analytical solutions to Markov processes can be considerably reduced by the application of symbol manipulation programs. Since many physical systems can be modeled by Markov and semi-Markov processes, the potential range of application of these techniques is much wider than the problem of availability analyzed here. [ABSTRACT FROM AUTHOR]

This paper presents methods for empirical evaluation of features of Instruction Set Processors (ISPs). ISP features are evaluated in terms of the time used or saved by having or not having the feature. The methods are based on analysis of traces of program executions. The concept of a register life is introduced, and used to answer questions like: How many registers are used simultaneously? How many would be sufficient all of the time? Most of the time? What would the overhead be if the number of registers were reduced? What are registers used for during their lives? The paper also discusses the problem of detecting desirable but non-existing instructions. Other problems are briefly discussed. Experimental results are presented, obtained by analyzing 41 programs running on the DECsystem 10 ISP. [ABSTRACT FROM AUTHOR]

Foreword. At every standards meeting, in clear view on the table there should be a small plaque engraved: "Do it once, do it right, do it internationally." The many contributions of Douglas Ross exemplify this directive. If, for example, you look at the ASCII standard, ANSI-X3.4-1968, you will find that D.T. Ross represented ACM on the ANSI X3 Committee at that time. This paper is part of an argument that well-founded standards go hand in hand with an effective systems methodology. When first submitted for refereeing, "Homilies for Humble Standards" was oriented toward Computer Aided Manufacturing (CAM) applications. As it is now published, the context is elevated to consider all applications. In a similar manner, we can broaden the scope to show that it is the concern of all ACM members. Manufacturing is the application of tools and processes on materials to create a product. Languages are our tools, algorithms and procedures are our processes, data is our material. The product is an enhancement of the power and span of control of the customer. I commend this paper for your reading as one of the relatively few in ACM publications which tell why ACM and its members should be "involved", it discusses an unsolved problem, rather than a solution looking for a problem. [ABSTRACT FROM AUTHOR]

In a companion paper to this, "I Methodology and Experiences," the automatic Clenshaw-Curtis quadrature scheme was described and how each quadrature formula used in the scheme requires a cosine transformation of the integrand values was shown. The high cost of these cosine transformations has been a serious drawback in using Clenshaw-Curtis quadrature. Two other problems related to the cosine transformation have also been troublesome. First, ... conventional computation of the cosine transformation by recurrence relation is numerically unstable, particularly at the low frequencies which have the largest effect upon the integral. Second, in case the automatic scheme should require refinement of the sampling, storage is required to save the integrand values after the cosine transformation is computed. This second part of the paper shows how the cosine transformation can be computed by a modification of the fast Fourier transform and all three problems overcome. The modification is also applicable in other circumstances requiring cosine or sine transformations, such as polynomial interpolation through the Chebyshev points. [ABSTRACT FROM AUTHOR]

Clenshaw-Curtis quadrature is a particularly important automatic quadrature scheme for a variety of reasons, especially the high accuracy obtained from relatively few integrand values. However, it has received little use because it requires the computation of a cosine transformation, and the arithmetic cost of this has been prohibitive. This paper is in two parts; a companion paper, "II Computing the Cosine Transformation," shows that this objection can be overcome by computing the cosine transformation by a modification of the fast Fourier transform algorithm. This first part discusses the strategy and various error estimates, and summarizes experience with a particular implementation of the scheme. [ABSTRACT FROM AUTHOR]

Because of the problems created by the explosion of papers in the mathematical sciences and the drawbacks that this places on research, it is suggested that a tree of all mathematical results and terminology be maintained in a multiterminal computer system. Users of the system can store in the computer an updated file of their current knowledge, and on selecting a paper to read, they can obtain from the computer the minimum subtree of theorems required to bring them from what they already know to the background knowledge which the paper assumes. Under certain conditions, means are also provided for the contribution of useful comments by the readers of a work and for interaction between commentators and with the author. This paper describes how the system can be organized and the role required of readers, writers, and commentators. [ABSTRACT FROM AUTHOR]

A comprehensive system for transformational grammar has been designed and implemented on the IBM 360/67 computer. The system deals with the transformational model of syntax, along the lines of Chomsky's Aspects of the Theory of Syntax. The major innovations include a full, formal description of the syntax of a transformational grammar, a directed random phrase structure generator, a lexical insertion algorithm, an extended definition of analysis, and simple problem-oriented programming language in which the algorithm for application of transformations can be expressed. In this paper we present the system as a whole, first discussing the general attitudes underlying the development of the system, then outlining the system and discussing its more important special features. References are given to papers which consider some particular aspect of the system in detail. [ABSTRACT FROM AUTHOR]

Sussenguth suggests in a paper (1963) that a file should be organized as a doubly-chained tree structure if it is necessary both to search and to update frequently. Such a structure provides a compromise between the fast search/slow update characteristics of binary searching and the slow search/fast update characteristics of serial searching. His method, however, contains the limiting restriction that all terminal nodes lie on the same level of the tree. This paper considers the effect of relaxing this restriction. First, trees which have the property that a priori the filial set of each node is well defined are studied. It is proved that coding the nodes within each filial set with respect to the number of terminal nodes reachable from each is necessary and sufficient to guarantee minimum average search time. Then the more general case (that is, where the entire structure of the tree is changeable) is treated. A procedure is developed for constructing a tree with a minimum average search time. A simple closed expression for this minimum average search time is obtained as a function of the number of terminal nodes. The storage capacity required to implement the doubly-chained tree structure on a digital computer is also determined. Finally, the total cost of the structure, using Sussenguth's cost criterion, is computed. It is shown that significant improvements in both the average search time and the total cost can be obtained by relaxing Sussenguth's restriction that all terminal nodes lie on the same level of the tree. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a comparison of some computer simulation languages and of some of the packages by which each is implemented. Some considerations involved in comparing software packages for digital computers are discussed In Part I. The issue is obvious: users of digital computers must choose from available languages or write their own. Substantial costs can occur, particularly in training, implementation and computer time if an inappropriate language is chosen. More and more computer simulation languages are being developed: comparisons and evaluations of existing languages are useful for designers and implementers as well as users. The second part is devoted to computer simulation and simulation languages. The computational characteristics of simulation are discussed with special attention being paid to a distinction between continuous and discrete change models. Part III presents a detailed comparison of six simulation languages and packages: SIMSCRIPT, CLP, CSL, GASP, GPSS and SOL. The characteristics of each are summarized in a series of tables. The implications of this analysis for designers of languages, for users, and for implementers are developed. The conclusion of the paper is that the packages now available for computer simulation offer features which none of the more general-purpose packages do and that analysis of strengths and weaknesses of each suggests ways in which both current and future simulation languages and packages can be improved. [ABSTRACT FROM AUTHOR]

This article focuses on the use of electronic voting systems in Georgia. The history of elections and computers in Georgia is unique. DeKalb and Fulton counties in the metro-Atlanta area were the first jurisdictions in the U.S. to use computers to tally votes in a primary election in October 1964. Georgia was the first state to adopt a uniform, statewide direct-recording electronic (DRE) technology in 2002. Georgia has a model system for the deployment and management of elections technology, which combines the resources of its Secretary of State (SOS), its University system, and its county election officials. In the general election of 2000 the voters in Georgia voted on a variety of election devices. Two of the smallest counties used hand-counted paper ballots, 73 counties voted on mechanical lever machines, 17 counties voted on punch-card voting systems, and 67 counties voted on optical-scan voting systems. Deployment of the DRE technology in the summer of 2002 was characterized by the conviction of the SOS that Georgia should eliminate technological barriers to voting, such as undervotes or spoiled ballots.

In the anticipated symbiotic partnership men will set the goals, formulate the hypotheses, determine the criteria, and perform the evaluations. Computing machines will do the routinizable work that must be done to prepare the way for insights and decisions in technical and scientific thinking. The current broadband infrastructure promises to bring huge volumes of information faster than ever before. Even now, reports, data, music, and movies flood our electronic paper worlds. Once only executives and researchers were required to handle large amounts of information. Today, home users are swamped with information from their broadband connections.

The article presents abstracts of research papers related to information technology. The research paper "Transactions and Consistency in Distributed Database Systems," discusses the concepts of transaction and data consistency for distributed computing systems. The cases of partitioned data, where fragments of a file are stored at multiple nodes, and replicated data, where a file is replicated at several nodes, are discussed. It has been argued that the distribution and replication of data should be transparent to the programs which use the data. That is, the programming interface should provide location transparency, replica transparency, and failure transparency. According to the research paper "On the Correct Translation of Update Operations on Relational Views," most relational database systems provide a facility for supporting user views. Permitting this level of abstraction has the danger, however, that update requests issued by a user within the context of his view may not translate correctly into equivalent updates on the underlying database.

Contrary to recent claims that specification should be completed before implementation begins, this paper presents two arguments that the two processes must be intertwined. First, limitations of available implementation technology may force a specification change. For example, deciding to implement a stack as an array (rather than as a linked list) may impose a fixed limit on the depth of the stack. Second, implementation choices may suggest augmentations to the original specification. For example deciding to use an existing pattern-match routine to implement the search command in an editor may lead to incorporating some of the routine's features into the specification, such as the ability to include wild cards in the search key. This paper elaborates these points and illustrates how they arise in the specification of a con- troller for a package router. [ABSTRACT FROM AUTHOR]

English logician and mathematician Alan Turing, in an attempt to develop a working definition of intelligence free of the difficulties and philosophical pitfalls of defining exactly what constitutes the mental process of intelligent reasoning, devised a test, instead, of intelligent behavior. The idea, codified in his celebrated 1950 paper "Computing Machinery and intelligence," was specified as an "imitation game'' in which a judge attempts to distinguish which of two agents is a human and which a computer imitating human responses by engaging each in a wide ranging conversation of any topic and tenor. Turing's reasoning was, presuming that intelligence only practically determinable behaviorally, that any agent that was indistinguishable in behavior from an intelligent agent was, for all intents and purposes,intelligent. It is presumably uncontroversial that humans are intelligent as evidenced by their conversational behavior. Thus, any agent that can be mistaken by virtue of its conversational behavior with a human must he intelligent.

It seems that the vision of the Internet grew out of the realization that users of the first, experimental time-sharing systems formed communities. The time-sharing experiments were funded by the Advanced Research Projects Agency of the U.S. Department of Defense, originally ARPA, now DARPA, under the leadership of J.C.R. Licklider, who had championed interactive computing in an influential paper on man-machine symbiosis. Licklider soon recognized the importance of electronic communities and the initial ARPANET development was funded. The ARPANET project refined the vision and pioneered techniques used on the Internet. It was followed by the Internet, which serves the research and education communities, and by many commercial and proprietary networks. The Internet, the major research and education network, grew from the 4-node ARPANET in 1969 to an estimated 992,000 hosts by September 1992. The growth rate is over 1,000 hosts per day, and it is accelerating. Its size can only be estimated, and continues to grow while, the estimation procedure runs.

The article presents a study on the impact of a computerized record system on work lives of customer service representatives in a large utility company. The study includes 10 offices employing a total of 485 service representatives in 6 cities. Top management decided to automate the customer service department to increase efficiency and cut labor costs. They installed equipment that would computerize information that service representatives had previously viewed on microfiche and altered by completing paper transaction records. Compared to the microfiche system it replaced, the interactive computer system was to provide service representatives with more recent billing information in a more convenient way and to allow interactive updating of customers' accounts. To provide the informational support for these customer contact tasks, each representative had a microfiche reader and a set of microfiche copies of recent bills for all accounts serviced by that office. Older bills were kept in a central storage area, and service representatives had to leave their desks to retrieve them.

Flexible representations are required in order to understand and generate expert behavior. Although production rules with quantifiers can encode experiential knowledge, they often have assumptions implicit in them, making them brittle in problem scenarios where these assumptions do not hold. Qualitative models achieve flexibility by representing the domain entities and their interrelationships explicitly. However, in problem domains where assumptions underlying such models change periodically, it is necessary to be able to synthesize and maintain qualitative models in response to the changing assumptions. In this paper we argue for a representation that contains partial model components that are synthesized into qualitative models containing entities and relationships relevant to the domain. The model components can be replaced and rearranged in response to changes in the task environment. We have found this "model constructor" to be useful in synthesizing models that explain and generate expert behavior, and have explored its ability to support decision making in the problem domain of business resource planning, where reasoning is based on models that evolve in response to changing external conditions or internal policies. [ABSTRACT FROM AUTHOR]

Applications of distributed processing networks are proliferating rapidly. It is expected that by the year 2000, distributed networks will be one of the most significant developments to evolve from the computer revolution. Distributed networks are unique in that they bring together concepts of communication, engineering, and computing. From an audit standpoint, the complexities involved in control design and testing are challenging. The auditor needs to be knowledgeable concerning these complexities in order to apply the proper audit tools, particularly since some of these tools are in need of improvement or development. This paper provides a summary of important areas of audit concern in distributed processing systems. [ABSTRACT FROM AUTHOR]

A common approach to the design of user interfaces for computer systems is the menu selection technique. Each menu frame can be considered a node in an information/ action network. The set of nodes and the permissible transitions between them (menu selections) form a directed graph which, in a system of substantial size, can be large and enormously complex. The solution to this problem of unmanageable complexity is the same for menu networks as for programs: the disciplined use of a set of well-defined one-in- one-out structures. This paper defines a set of such structures and offers some guidelines for their use. [ABSTRACT FROM AUTHOR]

System R, an experimental database system, was constructed to demonstrate that the usability advantages of the relational data model can be realized in a system with the complete function and high performance required for everyday production use. This paper describes the three principal phases of the System R project and discusses some of the lessons learned from System R about the design of relational systems and database systems in general. [ABSTRACT FROM AUTHOR]

This paper discusses a method for placing confidence limits on the steady state mean of an output sequence generated by a discrete event simulation. An estimate of the variance is obtained by estimating the spectral density at zero frequency. This estimation is accomplished through a regression analysis of the logarithm of the averaged periodogram. By hatching the output sequence the storage and computational requirements of the method remain low. A run length control procedure is developed that uses the relative width of the generated confidence interval as a stopping criterion. Experimental results for several queueing models of an interactive computer system are reported. [ABSTRACT FROM AUTHOR]

An important part of a simulation study is the analysis of simulation output for the purpose of making inferences about properties of the process being simulated. Fundamental to much of this analysis is the building of a confidence interval on the mean value of a key output variable of interest. This procedure is complicated by the possible presence of serial correlation in the output, which makes it difficult to estimate the variability in the estimator of the process mean. Although some research has been devoted to estimating this variability, additional research must be directed toward developing reliable confidence interval procedures and making the practitioner's selection of an appropriate procedure relatively straightforward. This paper provides a conceptual framework for research in the analysis of simulation output, focusing in particular on confidence interval methodology. The characteristics of confidence interval procedures, theoretical output processes, and processes of practical interest to simulation practitioners are discussed, and their relationships with one another spelled out. Standard measures of effectiveness applicable to proposed confidence interval procedures are introduced, and the application of these measures to two previously suggested confidence interval procedures is illustrated. [ABSTRACT FROM AUTHOR]

This paper identifies and analyzes technical and nontechnical biases in research on social issues in computing. Five positions—technicism, progressive individualism, elitism, pluralism, and radical criticism—which reflect major streams of contemporary social thought are examined The analysis of positions documents the close relationship between research policy formation and reveals the misleading and dangerous character of the presumption of scholarly objectivity in research on social issues. [ABSTRACT FROM AUTHOR]

This paper presents a model of an I/O subsystem in which devices can be accessed from multiple CPUs and/or via alternative channel and control unit paths. The model estimates access response times, given access rates for all CPU-device combinations. Central to the model's algorithm is the estimation of the rotational position sensing (RPS) miss probabilities by means of the maximum entropy principle. [ABSTRACT FROM AUTHOR]

Several letters to the editor commenting on the paper "Social Processes and Proofs of Theorems and Programs," by De Millo, Lipton and Perlis are presented.

The article presents news briefs concerning the Association of Computing Machinery (ACM). Mostek Corp. has become Corporate Member of ACM. ACM modified its own copyright procedures with respect to papers published in ACM journals. John Tartar has been appointed ACM Chairman of the External Activities Board.

This paper describes a new way of solving the storage reclamation problem for a system such as Lisp that allocates storage automatically from a heap, and does not require the programmer to give any indication that particular items are no longer useful or accessible. A reference count scheme for reclaiming non-self-referential structures, and a linearizing, compacting, copying scheme to reorganize all storage at the users discretion are proposed. The algorithms are designed to work well in systems which use multiple levels of storage, and large virtual address space. They depend on the fact that most cells are referenced exactly once, and that reference counts need only be accurate when storage is about to be reclaimed. A transaction file stores changes to reference counts, and a multiple reference table stores the count for items which are referenced more than once. [ABSTRACT FROM AUTHOR]

A security kernel is a software and hardware mechanism that enforces access controls within a computer system. The correctness of a security kernel on a PDP-11/45 is being proved. This paper describes the technique used to carry out the first step of the proof: validating a formal specification of the program with respect to axioms for a secure system. [ABSTRACT FROM AUTHOR]

This paper investigates mechanisms that guarantee secure information flow in a computer system. These mechanisms are examined within a mathematical framework suitable for formulating the requirements of secure information flow among security classes. The central component of the model is a lattice structure derived from the security classes and justified by the semantics of information flow. The lattice properties permit concise formulations of the security requirements of different existing systems and facilitate the construction of mechanisms that enforce security. The model provides a unifying view of all systems that restrict information flow, enables a classification of them according to security objectives, and suggests some new approaches. It also leads to the construction of automatic program certification mechanisms for verifying the secure flow of information through a program. [ABSTRACT FROM AUTHOR]

Consider a multipriority batch computer system which users from several different classes may join, with toll, service, and waiting charges. Such a system is formulated here as a semi- Markov decision process, In which the aim of arriving users Is to minimize their expected loss. The optimal joining policy of arriving users who may join the system at some of its queues is a control limit policy, with a single control number for any possible queue and the user's class; a newly arriving user will join a queue that is not filled up to the control number corresponding to this queue and the user's class. In this paper control numbers, as well as lower and upper bounds for the control numbers and the capacities of the system's queues, are derived. [ABSTRACT FROM AUTHOR]

The Designer Problem Solver (DPS) demonstrates that the computer can perform simple design tasks. In particular, it designs furniture and equipment layouts. This task was chosen because it is simple, welt defined, and characteristic of many design tasks in architecture, engineering, urban planning, and natural resource management. These space planning tasks usually involve manipulating two-dimensional representations of objects to create feasible or optimal solutions for problems involving topological and metric spatial constraints. The paper describes extensive tests performed on the program, DPS is a heuristic problem solver with a planning phase prefixed to It. It uses the planning process to give it a sense of direction, diagnostic procedures to locate difficulties, and remedial actions to recover from difficulties. It uses a convex polygon representation to accurately describe the objects and the layout. This representation allows topological and metric constraints to be tested and the design to be easily updated. ups has been applied to 50 problems. While it is slow and limited in scope, the ideas behind it are general. It demonstrates the need for selectivity in controlling search and the methods used to achieve it: task-specific information, planning, diagnostic procedures, remedial actions, and selective alternative generators. [ABSTRACT FROM AUTHOR]

GLYPNER is one of the earliest existing languages designed for programming the Illiac IV computer. The syntax of the language is based on ALGOL 60, but has been extended to allow the programmer explicitly to specify the parallelism of his algorithm in terms of 64-word vectors. This paper describes the characteristics, goals, and philosophy of the language, and discusses some of the problems associated with parallel computer architectures. [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]

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]

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]

This paper is concerned with certain aspects of contention for main memory resources in a multiproagrammed computer system operating under demand paging. In the model presented, the number of page- frames of main memory allocated to a problem program varies in time. These changes in memory configuration are represented explicitly in the model, CPU requirements and page exception characteristics of program material being described statistically. Expressions for the distribution of the number of page-frames allocated to an executing program, the long run expected fraction of a program's execution time in a given number of page-frames, and the average execution interval of the multi- programmed load are obtained. It is pointed out heuristically and demonstrated numerically that an increase is obtainable in the average execution interval of the multiprogrammed load over that resulting from equal fixed partitioning of main memory. [ABSTRACT FROM AUTHOR]