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The article discusses pricing aspects of cloud computing. The author notes similarities between cloud computing and timeshare computing, such as their adoption due to computing costs and labor needs. He notes that the use of open-source software and centralization of computer infrastructures have led to expectations of low pricing for cloud computing and notes cloud computing service models such as Infrastructure as a Service (IaaS), Platform as a Service (PaaS) and (Software as a Service (SaaS). He notes how a perfect competition market could form for cloud computing, resulting in variations in performance and the use of outdated hardware. Service-level agreements (SLAs) and technical support problems for cloud computing are noted.

Unlike the steady predictable hardware price⁄performance improvement described by Moore's law, there has been no such year to year progress in the user interface design. Instead, the history of user interfaces can be characterized using evolutionary biologist Steven Jay Gould's notion of punctuated equilibrium, long periods of stability interrupted by rapid change. People can identify four separate generations characterized by four distinguishable interface styles, each lasting for many years and optimized to the hardware available at the time. In the first period, the early 1950s and 1960s, computers were used in batch mode with punched card input and line-printer output. The second period in the evolution of interfaces , early 1960s through early 1980s was the era of timesharing on mainframes and minicomputers using mechanical or glass teletypes. During the 1980s, when desktop productivity tools began to be used by millions of people, it was recognized that above some minimal threshold of functionality and performance, the most important predictor of an application's success was its ease of use.

This article explains the operation structure and design of the computer networks Team Workstation and ClearBoard. Computer-supported cooperative work finished in the mid-1980s as an identifier interdisciplinary research field focused on the role computer and communication technology to support group work. Most of the current groupware systems are devoted to computational support and are designed under the constraint of limited communication bandwidth. However, the deployment of broadband digital networks opens a new future for multimedia collaboration environments that integrate real-time audio and video communication links with computer based shared workspaces. This article introduces the progression of iterative media design from Team Workstation to Clear-Board. These systems were designed to support focused real-time collaboration by distributed group members. The key concept behind the iterative design is seamlessness. People do a lot of their work without computers, or using different tools on different computer systems, and have developed their own work practices for these situations. INSET: Glossary..

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.

In 1989 the author projected that supercomputers would reach a teraflop by 1995 using either a SIMD or multicomputer approach, but neglected to mention the price. By mid-1992, scalable multicomputers have improved by a factor of 5 to 10 to reach 100 ± 20 Gflops at a supercomputer price level, and the SIMD approach was dropped. Scalable multicomputers also break through the $30 million supercomputer barrier to create a teraflop ultracomputer ($50 to 400 million), and are not recommended buys. In 1995 semiconductor gains should increase performance by a factor of four and competition should reduce the price a factor of two to supercomputer levels. Multiprocessors have been the mainline of computing because they are general-purpose and can handle a variety of applications from transaction-purpose and can handle a variety of applications from transaction-processing to time-sharing, that are highly sequential to highly parallel. Important gains in parallelism have come from software environments that allow networks of computers to be applied to a single job. INSET: Role of Computer and Computational Science..

Studies the nature and implementation of the UNIX time-sharing system. Features seldom seen in larger operating systems; Film system; Initiation of asynchronous processes; System command language.

The concept of one event happening before another in a distributed system is examined, and is shown to define a partial ordering of the events. A distributed algorithm is given for synchronizing a system of logical clocks which can be used to totally order the events. The use of the total ordering is illustrated with a method for solving synchronization problems. The algorithm is then specialized for synchronizing physical clocks, and a bound is derived on how far out of synchrony the clocks can become. [ABSTRACT FROM AUTHOR]

Describes the internal structure of a computer operating system as a set of cooperating sequential processes. Synchronization by means of semaphores and extended semaphores; Explanation of the semaphore constructions; Design principle; Discussion of project management and performance.

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]

Applies the dynamic verification of operating system decisions to the PRIME system being designed and constructed at the University of California in Berkeley. Background on PRIME, an experimental time-sharing system with the properties of continuous availability, data privacy and cost effectiveness; Details of the technique of dynamic verification; Advantages of using dynamic verification in PRIME.

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 behavior of a computer system is largely dependent upon the algorithms employed to allocate the system resources to the processes competing for them. Recent research in time-sharing paging systems has developed the working set model for program behavior, and a resource allocation strategy based on this model has been proposed. Two implementations along these principles have been reported, but it seems that in neither case have further results been announced. This report discusses the design and implementation of a dispatcher based on the working set principle, presents data to permit analysis of its behavior, and indicates future directions of research on methods of controlling a computer system. [ABSTRACT FROM AUTHOR]

A simulation model of a time-sharing system with a finite noncontiguous store and an infinite auxiliary store is used to study the variation of system parameters such as store size, number of jobs allowed to execute simultaneously, job-scheduling algorithm, etc. The effects of these variations on a measure of system performance is used to ascertain which of the parameters controllable by the job-scheduling algorithm, including the scheduling itself, require optimization, and which of the parameters not normally controllable by the scheduling algorithm have a marked effect on system performance. System performance is based upon the mean cost of delay to all jobs processed. It is shown that significant improvements in the measure of system performance can be obtained by using variable time-slice techniques and by selecting the optimum round-robin cycle time. It appears that these features would benefit from optimization whereas other parameters controllable by the scheduling algorithm affect system performance in a predictable manner and would not benefit from optimization. Features not normally under the control of the scheduling algorithm can also have a marked effect on the measure of performance; in particular, supervisor overheads, the size of the store, and the speed of the CPU. A comparison is made between the results of the simulation model and two analytical equations for quantum-oriented nonpreemptive time-sharing systems. The comparison is found to be very favorable. [ABSTRACT FROM AUTHOR]

Describes a system of communication between processes in a time-sharing system. Extension of the communication system for processes distributed throughout the computer network; Discussion on the hypothetical application of the system to an existing network.

Describes how the TENEX, a paged time sharing system implemented on a DEC PDP-10 augmented by special paging hardware, specifies a set of goals. Effect of time operational requirement on the implementation of the system; Constraints imposed by the scale of the system and available resources on the implementation of the system.

Presents a computer user program measurement in a time-shared environment. Implementation using a TX-2 computer; Operating systems; Multiprogramming systems; Measurement technology; Virtual computers; Performance improvement.

The services received by a process from a time-sharing operating system can be characterized by a resource count Σ wiRij where Rij is the number of units of service received by process j from resource i and wi is the cost per unit of the service. Each class of users can be characterized by a policy function which specifies the amount of service a user who belongs to this class should receive as a function of time. Priority changes dynamically as a function of the difference between the service promised to the user by the policy function and the service he actually receives. A scheduling and swapping algorithm which keeps the resource count of each process above its policy function will provide the specified level of service. Overhead can be reduced by avoiding swaps of processes which have received at least this level of service. The algorithm has been implemented in a general purpose operating system, and it has provided significantly better service to interactive and to batch jobs than the previous scheduler. [ABSTRACT FROM AUTHOR]

The effectiveness of certain time-sharing techniques such as program relocation, disk rotational delay minimization, and swap volume minimization is investigated. Summary data is presented, and the findings are discussed. The vehicle for this investigation was a SIMULA based simulation model reflecting an early framework for a planned Burroughs B6500 time-sharing system. Inasmuch as the B6500 system is based upon the use of variable sized segments and a dynamic overlay procedure, data is also presented which provides some indication of the effectiveness of this type of organization in a time-sharing environment. The design characteristics and operational capabilities of the simulation model are also described. [ABSTRACT FROM AUTHOR]

A facility to permit conversationally controlled tasks to be executed in a noninteractive environment is proposed. A means by which programs can generate interactive time-sharing commands and receive the corresponding output response is presented. The commands will be invoked as if they had been typed cit a console keyboard. It is argued that this facility will help overcome some of the current limitations in man-computer communication. A set of functions to accomplish the above which could be embedded into any string processing language is suggested, and necessary information pertinent to implementation of the facility on existing time-sharing systems is given. [ABSTRACT FROM AUTHOR]

Describes the question-answering aspects of the Protosynthex III prototype language processing system written in LISP 1.5 and operating on the Q-23 time-sharing system. Data structures; Semantic organization; Performance; Limitations of its question-answering capability.

A scheduling algorithm is proposed which is intended to minimize changes of tasks on processors and thereby reduce over-head. The algorithm also has application to more general resource allocation problems. It is implemented by means of a method for efficiently handling dynamically changing segmented lists. [ABSTRACT FROM AUTHOR]

Multiprogramming as it is discussed here is a mode of computer operation in which two or more programs are concurrently in processor memory and proceeding, each using the same central processor unit (CPU) and input-output (I/O) channels. These programs are actually proceeding intermittently and singly, according to eligibility (readiness to proceed) and priority. It is useful to be able to represent them as proceeding continuously and simultaneously, each at an effective rate, which may be a fraction of that which it would enjoy in the absence of the other programs. The effective progress rate of each program is sensitive to many detailed characteristics of itself and its co-residents; and simulation has been the best available method of predicting it. This paper presents the results of progress in developing an alternative to simulation, a simulation-tested iterative computation of these rates under certain situations. The algorithm is sensitive to most of the factors that control the phenomenon, including nonquantitative or topological features of the programs' structures. [ABSTRACT FROM AUTHOR]

Describes an experimental comparison of problem-solving using time-sharing and batch-processing computer systems. Use of the computer as an aid in decision-making and problem-solving; Cost for usage of the two systems.

Directed graphs or their associated matrices are frequently used to represent the logical structure of sequences of computer instructions. Such techniques are used and, in addition, data references are represented in a nondirected model. The complete structural specification of a program is represented by a combined model. A transformation of the combined model yields new model in which additional timing information is also contained. Analysis of these models prior to execution yields information valuable in determining segmentation of instructions and data for a time-shared environment, as well as for initial page loading; during execution, the analysis may be used for "look ahead" control of page turning. [ABSTRACT FROM AUTHOR]

Time-sharing systems, as defined in this article, are those multiaccess systems which permit a terminal user to utilize essentially the full resources of the system while sharing its time with other terminal users. It is each terminal user's ability to utilize the full resources of the system that makes quantitative evaluation of time-sharing systems particularly difficult. Six criteria are described which have been successfully used to perform first-level quantitative time-sharing system performance evaluation. [ABSTRACT FROM AUTHOR]

Task scheduling and resource balancing for a medium size virtual memory paging machine are discussed in relation to a combined batch processing and time-sharing environment. A synopsis is given of the task scheduling and paging algorithms that were implemented, and the results of comparative simulation are given by tracing the development of the algorithms through six predecessor versions. Throughout the discussion particular emphasis is placed on balancing the system performance relative to the characteristics of all the system resources. Simulation results relative to alternate hardware characteristics and the effects of program mix and loading variations are also presented. [ABSTRACT FROM AUTHOR]

Some basic concepts involved in the design of the MULTICS operating system are introduced. MULTICS concepts of processes, address space, and virtual memory are defined and the use of paging and segmentation is explained. The means by which users may share procedures and data is discussed and the mechanism by which symbolic references are dynamically transformed into virtual machine addresses is described in detail. [ABSTRACT FROM AUTHOR]

The onward sweep of automatic processing of information is impeded by nine principal barriers: geography, cost, problem complexity, man-machine communication, inadequate sensors, lack of understanding, distance, time, and size. The main incentive for breaching these barriers is the universal need for processing information, ever more urgent of the greater port of human work activity changes from production to service. Computer developments in hardware, programming, timesharing, education, data communication, and displays are judged by how effectively they remove these barriers, and their barrier-smashing potentialities indicate continued rapid expansion. Problem-oriented languages are particularly effective over the entire front. Online computers and time-sharing also rate high by this measure. Education and increased understanding are basic to all progress with the computer. This complex but powerful tool is the most important one available to governments and scientists to use in studying the problems being created by the population explosion, and in analyzing possible solutions. [ABSTRACT FROM AUTHOR]

Examines the debugging performance of programmers working under conditions of online and offline access to a computer. Indication of faster debugging under online conditions; Individual differences in programmer performance; Advantage of time-sharing systems.

Examines the use of Laboratory Computer Online Inquiry Monitor in non-numerical, time-sharing applications. Retrieval of non-numerical applications from large files using a dialogue between a system user and a retrieval application; Techniques for resource allocation; Scheduling on the use of core storage, computational facilities, and input-output; Program segments executed by the remote cathode ray tube consoles.

Describes a time-sharing system embedded within the standard batch processing system for the CDC 6600 computer. Facilities for file input, manipulation, editing, compilation and conversational execution; Implementation time; Scheme for system extension.

A general purpose, remote access, computing system is described, that employs twelve-key keyboard telephones as terminals. Audio output is provided directly to the telephone terminals, but the system will normally be used in conjunction with remotely located high speed printing devices. The system is a compatible extension of an existing batch processing system. A significant element of the system is a scheme for transmitting alphanumeric information by single strokes on a numeric keyboard. The programmed scanner uses context to eliminate the ambiguity in transmission. [ABSTRACT FROM AUTHOR]

The development of new large scale time-sharing systems has raised a number of problems for computation center management. Not only is it necessary to develop an appropriate hardware configuration for these systems, but appropriate software adjustments must be made. Unfortunately, these systems often do not respond to changes in the manner that intuition would suggest, and there are few guides to assist in the analysis of performance characteristics. The development of a comprehensive simulation model to assist in the investigation of these questions is described in this paper. The resulting model has a general purpose design and can be used to study a variety of timesharing systems. It can also be used to assist in the design and development of new time-sharing algorithms or techniques. For the sake of efficiency and greater applicability, the model was implemented in a limited FORTRAN subset that is compatible with most FORTRAN IV compilers. The use of the simulation is demonstrated by a study of the IBM 360/67 time-sharing system. [ABSTRACT FROM AUTHOR]

Techniques to make time sharing attractive on a computer with a small central memory are presented. "Small" is taken to mean that only one user program plus a monitor will fit into the memory at any time. The techniques depend on having two levels of secondary storage: level 1, several times larger than the main memory and quite fast; and level 2, many times larger and slower than level 1. [ABSTRACT FROM AUTHOR]

Presents interarrival statistics for time sharing systems. Assumption on the input process; Description of stochastic process governing the user inputs and the program activity; Illustration of input activity in channel interarrival time.

ELIZA is a program operating within the MAC time-sharing system at MIT which makes certain kinds of natural language conversation between man and computer possible. Input sentences are analyzed on the basis of decomposition rules which are triggered by key words appearing in the input text. Responses are generated by reassembly rules associated with selected decomposition rules. The fundamental technical problems with which ELIZA is concerned are: (1) the identification of key words, (2) the discovery of minimum context, (3) the choice of appropriate transformations, (4} generation of responses in the absence of key words, and (5) the provision of an editing capability for ELIZA "scripts." A discussion of some psychological issues relevant to the ELIZA approach as well as of future developments concludes the paper. [ABSTRACT FROM AUTHOR]

Describes a data input scheme for a time-sharing computer. How the computer asks the user for the required values one at a time instead of using format statements to determine the input; Computer's conversation with the user during the input process; Provision of standard data; Enabling of editing of values input.