Time-sharing Computer Research Articles

The Time-Shared Computer: A Teaching Tool

"Students still line up to use the teletypes, and we've had to keep the building open nights, Saturdays, school holidays, and during the summer vacation to meet the demand for extra computer time. It has been one of the single greatest motivating forces... that I have ex perienced as a high school principal."

Acquisition and Processing of Gas Chromatographic Data Using a Time-Shared Computer

Acquisition and Processing of Gas Chromatographic Data Using a Time-Shared Computer

Remote Access Computer Output over ITV Systems

The United States Military Academy at West Point, N. Y., has used a time-shared computer system in support of the academic program since 1965. The requirement has existed, however, for a highly flexible, portable access terminal-one more portable than the bulky communication or video units normally labeled as portable. It was felt that a terminal that could be used in any classroom or auditorium where the students could view both input and output would be far more suitable to the teaching environment. Such a terminal would allow instructors at West Point to use computers for reinforcement of teaching points and as a medium of demonstration. This requirement has been met through the integration of a PDP-8/I, a DF-32, and a video-display generator with the time share system and the instructional television system. Now the only equipment that has to be moved into the classrooms is a keyboard-entry device built into a 22-, by 16-, by 5-inch case. Since each classroom and auditorium has receivers placed to cover a maximum audience, the input and output is distributed via the instructional television system (ITV). The system is now fully operational. For in-class instructional support, it has proven itself an extremely flexible means of gaining access to the time-share system.

The Bell picturephone system

The Picturephone service, due to open in the United States in summer 1970, is a video-telephone system operating to a large extent over the existing telephone network. As well as face-to-face communication between subscribers, it can transmit graphical information and can be used in conjunction with a time-sharing computer to give subscriber—computer communication.

A Queueing Theory Study of Round-Robin Scheduling of Time-Shared Computer Systems

article Free AccessA Queueing Theory Study of Round-Robin Scheduling of Time-Shared Computer Systems Author: Philip J. Rasch Recognition Equipment, Inc., Dallas, Texas and Texas Instruments Inc., Dallas, Texas Recognition Equipment, Inc., Dallas, Texas and Texas Instruments Inc., Dallas, TexasView Profile Authors Info & Claims Journal of the ACMVolume 17Issue 1Jan. 1970 pp 131–145https://doi.org/10.1145/321556.321569Published:01 January 1970Publication History 25citation1,143DownloadsMetricsTotal Citations25Total Downloads1,143Last 12 Months56Last 6 weeks24 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

The use of a time-shared computer for control synthesis and design

The use of a time-shared computer for control synthesis and design

An Example of Early Quantitative Fundamental Stock Analysis

Lacking computers, financial analysis of investments prior to the sixties was seldom quantitative. Toward the end of the sixties, time-sharing computers with limited memory were available. Basic statistical analysis was feasible, and a few financial analysts with quantitative training began to try to gain an advantage over their colleagues by extracting what they viewed as private information from public data. This paper presents an example from 1969, an analysis of catastrophic insurance losses. Following Hurricane Betsy, that devastated Florida in 1965, many professional investors were fearful of catastrophic losses adversely impacting insurance stocks. This analysis allowed one buy-side boutique research firm to put Hurricane Betsy in perspective.

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.

A Method for the Design of Equalizers for High-Grade Channels Transmitted Over Telephone Cable Pairs of Mixed Gauges

The telephone exchange cable plant may be a mixture of several gauges in a particular run. Predicting its electrical behavior precisely when only one gauge is involved is difficult at best. Gauge mixtures and the lack of accurate records preclude the computational course in the practical case. A method is given for the graphical analysis of cable attenuation obtained from measurements. A means for locating the pole and zero frequencies of the equalizer network is described, as is the use of a frequency response slide rule for rapidly verifying the results. In addition, it is shown that the use of a time-sharing computer can be helpful in specifying components and in the general administration of equalizer projects when large numbers are involved.

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.

Time-Sharing--A Powerful Approach for Gas Chromatographic Data Reduction

The combination of a gas chromatograph, an electronic integrator, and a time-sharing computer system is a powerful tool for analyzing complex mixtures accurately and in detail. Time-sharing is a system of simultaneous computer service for multiple remote users. In this paper the above combination is used for the analysis of individual species in polydimethylsiloxane fluids, their trimethylsiloxy chain-stopper contents, prediction of response factors for species beyond the standards, and X-Y plots of molecular weight distributions.

An inexpensive gain stabilizer controlled by a time-shared computer

An electronic pulse amplifier is described for automatic gain correction in high-resolution high-rate pulse-height analysis systems. The circuit gain is controlled by a PDP-7 computer devoting less than 4 ms per second of its time to provide gain correction signals for up to 8 ampliers. Necessary control voltages are developed in the computer's CRT display circuits and transferred to a “sample and hold” circuit associated with each gain stabilizer. Gain control is accomplished by adjusting the gate voltage of an FET which shunts a small fraction of the total signal.

A Programmable Data Concentrator for a Large Computing System

Most large time-sharing computers require some sort of a data concentrator or multiplexor to accept inputs from a large number of low-speed remote terminals. Two major disadvantages of most of these concentrators are that they are nonprogrammable and relatively expensive. This paper describes the use of a small microprogrammed computer with a special instruction wired into the READ-ONLY memory to perform the multiplexing action. This approach has resulted in a programmable terminal controller which will handle up to 32 remotes, and provides enough processing capability to do code conversion and editing. This not only relieves the main computer of these routine tasks, but also reduces the amount and complexity of system modification within the main computer.

A modular computer sharing systems

An alternative approach to the design and organization of a general purpose interactive multiterminal computing system is presented. The system organization described is a conceptually simple arrangement of a bank of interchangeable computers, each of which is a memory/proputor pair, that are assigned to process terminal jobs as they arrive. One of the computers serves as the master or control computer and supervises the collection and distribution of messages from and to the remote terminals. In the simplest form there is a disk drive for each connected terminal. A crosspoint switching network allows any such disk drive to be connected to any computer in the bank, under control of the control computer. Thus, while each active terminal user “occupies” a dedicated disk drive, he may share the computer with many other terminal users in a simple manner. The ratio of users to computers is dependent on both the size and power of the machines used and the computation requirements of the particular mix of users. This system organization is inherently a simpler and therefore more reliable approach to time-sharing computers and has the potential of a highly available system at relatively low cost. Economic configurations are possible for a range of systems sizes that span at least one order of magnitude. Finally, problem programs developed by remote terminal users can be run on a dedicated batch system if compatible computers are used.

A time-sharing computer system for hospital information processing.

A time-sharing computer system for hospital information processing.

Computer evaluation of acid-base disorders

With the advent of electronic computers that operate in the time-sharing mode, it has become possible to develop an automated system that can assist a physician in solving clinical problems. In the present study a teletype terminal has been linked to a time-sharing computer which has been programmed to evaluate clinical and laboratory information concerning patients with acid-base disorders. The program checks the data for evidence of internal consistency and requests additional information as needed to solve the acid-base aspects of the clinical problem. If sufficient information is provided, the program generates an evaluation note designed to review with the physician the pathophysiology of the disorder and to assist him in its management. If the input data are incomplete, the program draws the most useful conclusions possible based on the data provided, specifies the limitations which pertain to these conclusions, suggests further studies designed to circumvent these limitations, and while awaiting the results, suggests appropriate interim therapeutic measures. The time required to enter a patient's data and to print the evaluation note is approximately 4 min; the cost is comparable to that of many laboratory tests.

Teaching of Transistor Circuit Design Using a Digital Computer

The availability of rapid on-line computational facilities has forced a major revision of our course on multistage transistor amplifiers. Approximate methods of analysis are now no longer helpful: the exact gain and bandwidth can be readily calculated on a computer. However, previously derived approximate relations for bandwidth can be inverted to provide excellent first-order design equations. The resulting first-cut design can then be checked on a computer and modified, if necessary, to more closely meet the design specifications. By using a time-shared computer facility (APL) 1 we have been able for the first time to involve the students in a meaningful and exciting way in the design of sophisticated multistage transistor amplifiers.

DIPNET: A General Distributed Parameter Network Analysis Program

The DIPNETcomputer program makes practical the simple and rapid solution of elaborate microwave networks on a time-sharing computer. Given a file of input data describing a DIstributed Parameter NET-work of electrical sections, the program finds the complex voltage and current phasors along the network over a prescribed range of frequencies. Sections may consist of a variety of transmission lines, lumped constants, sources, and active devices. Network configurations may include chains, side stubs, and two-path sections. The network size is practically unlimited, and may easily comprise hundreds of sections. Output data at selected points along the network may include phasors, their absolute magnitude and phase shift, and power flow. Normalization to designated phasors is provided for by the program. The output data may also include input resistance, reactance, impedance, and the admittance counterparts. Repeated sequences may be handled automatically. Network parameters may also be modified automatically, both those which depend on frequency and frequency-independent parameters.

General Purpose Programs for the Frequency Domain Analysis of Microwave Circuits

This paper describes microwave circuit analysis programs techniques for general purpose which perform frequency domain analyses. Differing techniques used in two programs are described. The first uses transfer matrix analysis and is limited to networks having tree structured topologies and two-port devices such as transmission lines, stubs and lumped elements. It runs on a time-shared computer and is used for interactive design. The second program can analyze any linear network including those with multiport elements such as coupled transmission lines. This uses a nodal representation for the circuit and relies on inverting an admittance matrix to perform the analysis. In the first program the user describes his circuit in terms of topology as well as circuit elements. By this technique, a considerable reduction in computer size needed to run this program is effected. A 60 element circuit can be run on a commercial time-sharing service with less than 6K words of available core. The second program requires a large computer; for example, 32K words or core storage are required to analyze a 50 node circuit.

A Computer Aided Decision System

The use of on-line, real-time computer-based information systems to augment managerial decision making raises interesting and significant questions. In search of operational answers, the authors have developed and conducted experiments with a time-sharing computer model. By modeling the dynamics of a job shop the authors were able both to make use of and to evaluate academic research in job shop scheduling. The authors have devised a specific apportionment of the problem environment which permits users of their information system to explore the effects of various combinations of heuristics and programmed decision rules. The response of over 300 managers and academicians who have participated in the experiments provides evidence of the practicality of such an approach to multi-dimensional, time-variant problem solving.