Time-sharing Computer System Research Articles

Results of Parallel-Flow Stability Calculations Obtained by Time-Sharing Computations

A series of programs for calculation of eigenvalues and eigenfunctions for parallel incompressible flow have been developed for use on the Massachusetts Institute of Technology time-sharing computer system. The programs were designed building-block fashion allowing a great variety of combinations of velocity profiles and boundary conditions (flexible walls, etc.) to be treated. Also, running instructions are built into the programs themselves and communicated to the user dialog-fashion during the run making their use very simple for anyone with a minimum of prior instructions thus greatly facilitating numerical experimentation. The program system serves, in effect, as an extensive and rather complete set of tables of solutions for the problem area considered. Several examples are shown and discussed such as channel and boundary-layer flows with and without inflection points, boundary layers over compliant surfaces, comparisons between viscous and inviscid calculations, and wave propagation constants for a turbulent boundary layer. The efficiency of the particular method employed for supressing numerical instability is also discussed.

Mean Response Times in Accessing a Time-Sharing Computer

In a time-sharing computer system a queueing problem arose whose solution could not be found easily using classical queueing techniques. The assumption of an exponential distribution for the time between arriving messages has enabled a theory to be constructed to find the average response times for customers. Since the system modelled is a simple interrogation service the analysis and results should be of general use. In particular the distributions of service times required by the customers can be quite general.

A time-sharing computer system for hospital information processing.

A time-sharing computer system for hospital information processing.

Degree of multiprogramming in page-on-demand systems

A simple stochastic model is described which offers a base for understanding the relationship between the number of programs permitted to share memory (the degree of multiprogramming), drum traffic rates, and central processing unit utilization in page-on-demand, multiprogrammed, time-shared computer systems. The model preserves, as a key feature, the property of page-demand statistics which implies a “burst” of page demands at the beginning of any job or quantum execution. The model, a Markov chain, is analyzed numerically and the results are presented graphically for a wide range of key environment-descriptive parameters. Implications of the results to time-shared system design and programming are discussed, and a calculation of the optimal degree of multiprogramming for a wide range of parameters is presented graphically.

The dynamod model of student and teacher population growth

DYNAMOD II is a computerized Markov-type model which calculates data for 140 population groups over selected intervals of time. These population groups are crossclassified as to sex, race (2 categories), age (6 categories), educational status (3 levels of students and teachers respectively, as well as elementary and secondary school dropouts), and an “other” category. The model employs over 832 transition probabilities to cycle the population groups. Independent birth projections are added to the appropriate sex-race categories after each interaction. The model is programmed for the RCA 3301 and GE time-sharing computer systems. On the GE system, a data file arrangement permits on-line access to any of the inputs or probabilities. In addition, user options regarding the desired amount of detailed output are available. DYNAMOD II can provide the educational community with estimates of the impact on the educational population of proposed policy changes or of sudden shifts in the structure of the educational system. For example, if policymakers wish to know what effect will be produced by a policy designed to decrease the elementary-school teacher turnover by one percent, DYNAMOD II can supply not only information on the new levels of teacher projections, but also can provide estimates of the rate at which these adjustments will take place. Not only are these estimates possible for the various tiers of student and teacher structures in the model, but changes outside the educational system, such as in birth and death rates can be handled as well. It follows that the impact of policy changes on policy tools, such as the student-teacher ratio, can also be estimated with the use of DYNAMOD II.

Automated chemistry laboratory: Application of a novel time-shared computer system

A promising strategy for providing a hospital information system is the gradual development and subsequent integration of well-defined information processing modules. A computer system which is suitable and economical to serve one or more of these modules has been developed. Its unique feature is that it uses an interpretive language for all the application programs both in the developmental and service modes of operation. The interpretive language, which has been designed specifically for data management applications, facilitates the creation and debugging of programs; in addition, it allows the time-sharing of a relatively small computer with a negligible overhead for switching control from one program to the next. The multiterminal, real-time remote-access computer system has been in service operation at the Clinical Chemistry Laboratory of the Massachusetts General Hospital since the early Fall of 1968. Presently, the system accepts typed-in requisition information, creates patient files, and generates schedules for centrifuging blood samples and for the performing of all tests; the system also accepts test results and provides reports on individual patients. In the near future all test results will be manually entered into the machine, which will then generate cumulative test reports each day. The on-line connection of automated laboratory equipment (AutoAnalyzers) will soon follow. Analysis of the system performance shows that the use of an interpretive language is suitable for this application, and it also indicates that the system has sufficient capacity for serving additional information processing needs.

The Computer as an Aid in Teaching Statistics

SUMMARY The authors discuss some of the different ways in which a computer may be used as a teaching aid in statistics courses, with particular reference to the use of time-sharing computer systems. THE electronic computer has had a considerable influence on statistical practice, for example complex multivariate analyses are now commonplace, but as yet has had little influence on teaching practice. In the U.K. this has been due in part to the shortage of adequate computing facilities, but also to the slowness of teachers to recognize the pedagogic value of the computer and to the inertia generated by rigid syllabuses and examination-oriented teaching. In the U.S.A. the position appears to be similar but there are notable exceptions, as witness the papers of Meyer (1965) and Sterling and Pollack (1966). These teachers have integrated the computer into their teaching programmes with great success. In this paper we examine some of the consequences of using a computer as a teaching aid in statistics courses. Our own work is as yet far from complete and the main object is to clarify our own ideas and to broadcast the ideas of others. We recognize that we have been as slow as others in actually implementing some of the ideas discussed, but we hope that our ideas and experience may nevertheless aid and stimulate others who are concerned with improving the productivity of their teaching. We find it useful to distinguish between several types of user of statistical method: (i) computing specialists with some knowledge of statistics; (ii) statistics specialists with some knowledge of computing; (iii) applied statisticians with detailed knowledge of the methods relevant to their field of application, for example economics or biology, but little knowledge of computing; (iv) non-statisticians such as sociologists or economists, who sometimes need to apply statistical methods and often need to use computers to handle large quantities of data. The requirements of these groups vary and the content of courses and method of teaching must vary accordingly. The computing specialist will need to know several programming languages and will probably learn his statistics as an application of these. This often means that he is weak in his understanding of concepts and this is

Außenstationen und Unterzentralen in Teilnehmer- Rechensystemen / Outstations and concentrators in time-sharing computer systems

Article Außenstationen und Unterzentralen in Teilnehmer- Rechensystemen / Outstations and concentrators in time-sharing computer systems was published on December 1, 1968 in the journal it - Information Technology (volume 10, issue 1-6).

A direct access computer program for control-theoretical computations

A brief description is given of a computer program for control-theoretical computations implemented by the authors on a direct access time-sharing computer system.

Computer analysis of cardiac catheterization data

The recent introduction of time-sharing computer systems allows several different investigator to use simultaneously the same computer for analysis of real time data. This paper reports on a computer program written for such a system to perform on-line analysis of data from a cardiac catheterization laboratory. Physiologic analog signals from the patient were transmitted to an analog-to-digital conversion unit, which was attached to an IBM 1800 Process Control Computer. After conversion, the data were transferred by the 1800 into an IBM 360/50 digital computer, which was programmed to analyze atrial pressure, ventricular pressure, peripheral pressure (aortic or pulmonary artery), wedge pressure, brachial artery pressure and cardiac output signals obtained during both right and left heart catheterizations. After pertinent data were obtained from the basic signals, the computer was programmed to calculate various derived values, such as systolic and diastolic time intervals, valve gradients, valve areas, stroke work, stroke power and vascular resistances. Important technics were the use of on-off switches to communicate directly with the computer, interaction between the computer and the cardiologist, and safeguards to assure the cardiologist that accurate data were presented for analysis. Preliminary results indicate that such a program and hardware system can be used without specially trained personnel to analyze rapidly and accurately data obtained during cardiac catheterization.

Queues with Feedback for Time-Sharing Computer System Analysis

A time-sharing computer system brings the man with a problem much closer to the computer power he needs. The priority processing problems associated with time-sharing computer system are described. A mathematical model was developed based on queues with feedback. The queue size and its variability within the computer can be determined with the enclosed formulation. Other important system design parameters such as the system response time, etc., can also be obtained. The mathematical model complements standard simulation techniques for time-sharing computer analysis. Although the problems discussed in this paper arose in the computer systems, the queuing model developed is quite general and may be useful for other industrial applications.

On-line control, data collection, and reduction for chemical experiments at Berkeley

A small time-shared computer system has been developed at the Department of Chemistry, University of California at Berkeley. This system is primarily aimed at control, data collection and data reduction of on-line chemical experiments. A description of the interface between the computer and our microwave spectrograph is given as an example of the kind of computer-instrument interaction possible with this system. Several results in microwave spectroscopy are given and various methods of digitally filtering the data are discussed.

Human factors and the design of time sharing computer systems.

The advent of computer time sharing poses an extraordinary challenge to human factors research during the next decade. Before time sharing, two facts combined to de-emphasize the importance of human factors considerations in the design of computer systems: (1) the cost of the computer's time was exorbitantly high relative to the cost of users' time, and (2) the users constituted a select, highly skilled and highly motivated group of specialists. Two of the promises of time sharing, however, are (1) a drastic reduction in the cost of computer time to the individual user, and (2) the large scale availability of computer facilities to individuals untrained in any areas of computer technology. Human factors considerations then become important both for economic and psychological reasons. This paper briefly notes what a few of these considerations are.

An analysis of time-shared computer systemsby A. L. Scherr

<i>An analysis of time-shared computer systems</i>by A. L. Scherr

A time-sharing computer system for patient-care activities

An experimental, time-sharing, remote-access computer system is being developed as part of a research project in the use of automatic data-processing techniques in patient-care procedures in the Massachusetts General Hospital. Programs have been designed that allow a user on a patient-care unit to order medications, retrieve laboratory test results, admit and discharge patients, etc. These programs are still in an experimental phase and duplicate the present hospital function. The system is designed to take advantage of the total data base in the computer storage to carry out operations which would be impossible using present methods. One such feature allows the routing of a message or the modification thereof to be determined by the contents of the message, and by the state of the data base. Because the system will be used by nontechnical individuals, the programs have been designed to appear to the user in a “conversational mode”, where in the computer types a question and the user a response.

LINGO—A programming language for linear network analysis at a remote teletype terminal

LINGO is a special-purpose programming language developed for computer-aided analysis of linear networks at a remote terminal of a time-sharing computer system. A special compiler (written in FORTRAN) enables the computer to read and execute LINGO programs, and the complete system can be implemented on very small computers (The General Electric Time-Sharing System, on which LINGO was developed, allots to the user only 5300 locations in core memory.) Taking full advantage of the conversational interaction with the computer, the engineer can proceed from the rough idea of the circuit diagram, through writing the LINGO program, to execution and tabulated results within 20 minutes or less. Having access to such a tool encourages the use of the computer as a real desk-side aid to linear network analysis.

An executive program for a time-shared on-line computer system

An executive program for a time-shared on-line computer system

Dynamic Articulatory Model of Speech Production

A dynamic articulatory model of speech production is described. From a discrete phonemic input, it generates a continuous description of the configuration of the articulatory mechanism in a midsagittal section. The model is divided into a “state” and “operators,” which act as agents for modifying the state by trying to manipulate it (i.e., responding articulatory structures) toward abstract “goals.” This bifurcation allows many of the constraints of the real system to be included in the model in a natural manner. By this means, the contextual effects of connected speech can be generated by less ad hoc methods than usually required by other schemes of speech modeling and/or synthesis. The present model concerns itself only with vowels and stops, but it is felt that the general methodologies are applicable to all speech sounds. A motion-picture film of model action, as simulated on a large time-shared computer system, is shown. [Work supported in part by the U. S. Air Force Cambridge Research Laboratories, Office of Aerospace Research, and by Project MAC, and MIT research program sponsored by the U. S. Department of Defense.]

Optimization of stochastic finite state systems

A class of stochastic dynamic systems is considered in which the set S of allowable states, the set Q of all the inputs, and the set O of the outputs are all finite. For the subclass of the systems in which the state can be exactly measured, a method is given to find the optimal control, so as to optimize a suitable criterion function. The set of probabilities Prob(q(t) = q_{k}/s(t) =s_{j}), q_{k} \in Q, s_{j} \in S , where q(t) and s(t) are the input and state at time t , respectively, plays the role of control. The determination of the optimal control involves only a solution of a set of N difference equations, where N is the total number of states. These results will be extended for systems in which the measured output is noisy. In this case, by control one means the set of probabilities Prob (q(t) = q_{k}/y(1),... , Y(t)), q_{k} \in Q where y(t) is the measured output at time t . These probabilities are found to be products of the current estimate of the state of the system s(t) , based on all the available measurements with certain precomputable constants. These results are applied to the analysis of time-sharing computer systems like project MAC, and demonstrate how to choose an optimal queue discipline among the various available queue disciplines for scheduling the various users.

Analysis of a time-shared computer system

Analysis of a time-shared computer system