As computers become more powerful and sophisticated, computational astrophysicists will be able to find out more about stellar evolution and other astronomical phenomena.
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Special-purpose processors in theoretical physics
Specially designed processors can provide a method for attacking some of the difficult computational problems facing theoretical physicists.
Symbolic mathematical computation
Standard programming languages are inadequate for the kind of symbolic mathematical computations that theoretical physicists need to perform. Higher mathematics systems like SMP address this problem.
Experimental mathematics: the role of computation in nonlinear science
Computers have expanded the range of nonlinear phenomena that can be explored mathematically. An “experimental mathematics facility,” containing both special-purpose dedicated machines and general-purpose mainframes, may someday provide the ideal context for complex nonlinear problems.
Designing for usability: key principles and what designers think
This article is both theoretical and empirical. Theoretically, it describes three principles of system design which we believe must be followed to produce a useful and easy to use computer system. These principles are: early and continual focus on users; empirical measurement of usage; and iterative design whereby the system (simulated, prototype, and real) is modified, tested, modified again, tested again, and the cycle is repeated again and again. This approach is contrasted to other principled design approaches, for example, get it right the first time, reliance on design guidelines. Empirically, the article presents data which show that our design principles are not always intuitive to designers; identifies the arguments which designers often offer for not using these principles—and answers them; and provides an example in which our principles have been used successfully.
Pricing computer services: queueing effects
This article studies the effects of queueing delays, and users' related costs, on the management and control of computing resources. It offers a methodology for setting price, utilization, and capacity, taking into account the value of users' time, and it examines the implications of alternative control structures, determined by the financial responsibility assigned to the data processing manager.
Computer science in secondary schools: curriculum and teacher certification
Computer science in secondary schools is an area of increasing interest and concern to educators as well as to computer science professionals. Each of the next two reports addresses an issue of major importance regarding computer science in secondary schools. The first report recommends computer science courses for the secondary school curriculum, and the second report recommends requirements for teacher certification in computer science.In 1983 the ACM Education Board initiated efforts to formulate recommendations for secondary school computer science. Two task forces, one for curriculum recommendations and the other for teacher certification recommendations, were established under the Education Board's Elementary and Secondary Schools Subcommittee. The work of the two task forces was also supported by the IEEE Computer Society Educational Activities Board, and the final reports from the task forces were jointly approved by the ACM and IEEE-CS boards in July 1984. Thus the reports are significan't not only for the important issues that they address, but also because they represent a joint activity between ACM and the IEEE Computer Society.The work of the two task forces is summarized in the next two reports. The full reports are available as the publication Computer Science in Secondary Schools: Curriculum and Teacher Certification, Order Number 201850, from the ACM Order Department, P.O. Box 64145, Baltimore, MD 21264.
An evaluation of retrieval effectiveness for a full-text document-retrieval system
An evaluation of a large, operational full-text document-retrieval system (containing roughly 350,000 pages of text) shows the system to be retrieving less than 20 percent of the documents relevant to a particular search. The findings are discussed in terms of the theory and practice of full-text document retrieval.
Predicting performance in an introductory computer science course
A group of 269 first-semester freshmen was used to predict both performance in an introductory computer science course and first-semester college grade point average by using information regarding the students' programs and performance in high school along with American College Testing Program (ACT) test scores.
A system for interactive viewing of structured documents
An existing typesetting system is tied by bridging software to an existing page-presentation program to effect both hard (typeset) copy and interactive browsing. The typesetting system formats documents for a variety of output devices, and the “browsing” feature appears to the user as simply another output device that happens to be interactive.
Programmer perceptions of productivity and programming tools
Psychometric scaling methods are applied to programmer productivity assessments of 20 tools to recommend a set of minimal, as well as more comprehensive, tools.
A specification language to assist in analysis of discrete event simulation models
Effective development environments for discrete event simulation models should reduce development costs and improve model performance. A model specification language used in a model development environment is defined. This approach is intended to reduce modeling costs by interposing an intermediate form between a conceptual model (the model as it exists in the mind of the modeler) and an executable representation of that model. As a model specification is constructed, the incomplete specification can be analyzed to detect some types of errors and to provide some types of model documentation. The primitives used in this specification language, called a condition specification (CS), are carefully defined. A specification for the classical patrolling repairman model is used to illustrate this language. Some possible diagnostics and some untestable model specification properties, based on such a representation, are summarized.
Rating the major computing periodicals on readability
The readability of the ten major computing periodicals is analyzed using the Flesch Reading Ease Index.
User-oriented criteria for the selection of DSS software
Both the composition of the selection team and the choice of evaluation criteria should reflect the end-user orientation of DSS software.
From programming language design to computer construction
From NELIAC (via ALGOL 60) to Euler and ALGOL W, to Pascal and Modula-2, and ultimately Lilith, Wirth's search for an appropriate formalism for systems programming yields intriguing insights and surprising results.
Grosch’s law re-revisited: CPU power and the cost of computation
Does Grosch's law, which postulated that the costs of computer systems increase at a rate equivalent to the square root of their power, still hold? The age of mini-, micro-, and supercomputers seems to have complicated the situation. When computers are grouped according to their size and power, Grosch's law seems to hold within each group, but not between different groups.
Amortized efficiency of list update and paging rules
In this article we study the amortized efficiency of the “move-to-front” and similar rules for dynamically maintaining a linear list. Under the assumption that accessing the ith element from the front of the list takes &thgr;(i) time, we show that move-to-front is within a constant factor of optimum among a wide class of list maintenance rules. Other natural heuristics, such as the transpose and frequency count rules, do not share this property. We generalize our results to show that move-to-front is within a constant factor of optimum as long as the access cost is a convex function. We also study paging, a setting in which the access cost is not convex. The paging rule corresponding to move-to-front is the “least recently used” (LRU) replacement rule. We analyze the amortized complexity of LRU, showing that its efficiency differs from that of the off-line paging rule (Belady's MIN algorithm) by a factor that depends on the size of fast memory. No on-line paging algorithm has better amortized performance.
This is the third report prepared by the ACM Committee on Scientific Freedom and Human Rights (CSFHR). The first was published in the March 1981 Communications and the second in the December 1982 issue. This report is an update. Since the committee intends to publish future updates, it would appreciate receiving further information about computer scientists whose rights have been violated. Such information should be sent to: Jack Minker, Vice-Chairman, Committee on Scientific Freedom and Human Rights, Department of Computer Science, University of Maryland, College Park, MD 29742.Because those whose scientific freedom or human rights have been violated derive sustenance and support from contacts with their colleagues, the CSFHR has established a program in which ACM chapters “adopt” individual scientists and correspond with them. Such correspondence should touch on the personal and scientific and not discuss political matters. These letters greatly improve the morale of the recipients and are one of the few ways they can keep current with computer science and technology. This CSFHR program is directed by Helen Takacs (P.O. Drawer CS, Mississippi State, MS 39762).
The Manchester prototype dataflow computer
The Manchester project has developed a powerful dataflow processor based on dynamic tagging. This processor is large enough to tackle realistic applications and exhibits impressive speedup for programs with sufficient parallelism.
Reduced instruction set computers
Reduced instruction set computers aim for both simplicity in hardware and synergy between architectures and compilers. Optimizing compilers are used to compile programming languages down to instructions that are as unencumbered as microinstructions in a large virtual address space, and to make the instruction cycle time as fast as possible.
Sixty-four small computers are connected by a network of point-to-point communication channels in the plan of a binary 6-cube. This “Cosmic Cube” computer is a hardware simulation of a future VLSI implementation that will consist of single-chip nodes. The machine offers high degrees of concurrency in applications and suggests that future machines with thousands of nodes are both feasible and attractive.
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