Controlling process plants using computers has always had spectacular failures as well as successes. A modern distributed control system (DCS) is very powerful, incorporating multitasking multiprocessors. However, unl...
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Controlling process plants using computers has always had spectacular failures as well as successes. A modern distributed control system (DCS) is very powerful, incorporating multitasking multiprocessors. However, unless this power is controlled, severe technical difficulties frequently arise, causing over spending and lateness. Multitasking and multiprocessing environments allow a number of application programmes to be active simultaneously. Academics have identified and analysed the problems of interfacing application programmes operating in these environments. A number of standard solutions, which co-ordinate both the information exchange and operation of the programmes, are now widely accepted. Unfortunately these have not yet been incorporated into distributed control systems, instead only limited lower level facilities are provided. However, the application programmer can implement these solutions using what facilities are provided. The author explains how this may be achieved and outlines the benefits of doing so.< >
The shared use of general-purpose uniprocessors is examined. Support for common uniform-memory-access architectures that have all memory equidistant from all processors in terms of access time is emphasized. This work...
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The shared use of general-purpose uniprocessors is examined. Support for common uniform-memory-access architectures that have all memory equidistant from all processors in terms of access time is emphasized. This work is also applicable to non-uniform-memory-access machines, whose memory access times depend on the physical distance between the processor and the accessed memory, but it does not provide a complete solution to load-balancing problems for this class of machine. The discussion covers time-sharing scheduling, the Mach scheduler, programming models, scheduling concurrency support, processor allocation, and related work
Some necessary background in speech recognition and window systems is given, with an analysis of how they might be combined. Xspeak, a navigation application, and its operation and a field study of its use are describ...
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Some necessary background in speech recognition and window systems is given, with an analysis of how they might be combined. Xspeak, a navigation application, and its operation and a field study of its use are described. With Xspeak, window navigation tasks usually performed with a mouse can be controlled by voice. An improved version, Xspeak II, which incorporates a language for translating spoken commands, is introduced
Four basic algorithms for implementing distributed shared memory are compared. Conceptually, these algorithms extend local virtual address spaces to span multiple hosts connected by a local area network, and some of t...
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Four basic algorithms for implementing distributed shared memory are compared. Conceptually, these algorithms extend local virtual address spaces to span multiple hosts connected by a local area network, and some of them can easily be integrated with the hosts' virtual memory systems. The merits of distributed shared memory and the assumptions made with respect to the environment in which the shared memory algorithms are executed are described. The algorithms are then described, and a comparative analysis of their performance in relation to application-level access behavior is presented. It is shown that the correct choice of algorithm is determined largely by the memory access behavior of the applications. Two particularly interesting extensions of the basic algorithms are described, and some limitations of distributed shared memory are noted
A description is given of a novel design, using a hierarchy of controllers, that effectively controls a multiuser, multiprogrammed parallel system. Such a structure allows dynamic repartitioning according to changing ...
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A description is given of a novel design, using a hierarchy of controllers, that effectively controls a multiuser, multiprogrammed parallel system. Such a structure allows dynamic repartitioning according to changing job requirements. The design goals are examined, and the principles of distributed hierarchical control are presented. Control over processors is discussed. Mapping and load balancing with distributed hierarchical control are considered. Support for gang scheduling as well as availability and fault tolerance is addressed. The use of distributed hierarchical control in memory management and I/O is discussed
Addresses the area of graphical user interfaces (GUIs) and open systems. In particular, the author talks about tools available that allow one to use GUIs to provide seamless integration between a variety of different ...
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Addresses the area of graphical user interfaces (GUIs) and open systems. In particular, the author talks about tools available that allow one to use GUIs to provide seamless integration between a variety of different open systems architectures. The role of GUIs in the future development of computer applications for open systems is stressed. The interworking of DOS, Unix and their GUIs is discussed.< >
The author describes the development of a high productivity software environment for generating test programs. The main aim was to make a system which would be very easy to use, having a minimal learning curve and min...
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The author describes the development of a high productivity software environment for generating test programs. The main aim was to make a system which would be very easy to use, having a minimal learning curve and minimising the need for detailed knowledge of the wide range of test equipment available today. The IBM PC was selected as the host computer to run the software and Microsoft Windows as the environment. The use of a multitasking environment offered the possibility of communications with other applications for processing and presentation of test results.< >
Developing graphical user interfaces (GUIs) such as the OS/2 Presentation Manager or Microsoft Windows is characterised by the use of large function call libraries, usually known as APIs (application programmer interf...
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Developing graphical user interfaces (GUIs) such as the OS/2 Presentation Manager or Microsoft Windows is characterised by the use of large function call libraries, usually known as APIs (application programmer interfaces), coupled with an event-driven program structure which is completely different to normal procedural programming. These two factors contribute to the long, shallow learning curve associated with becoming expert in this type of programming. GUI applications also tend to have far more code involved than a textual application, again because of the richness and complexity of the environment. CASE:PM and CASE:W tools are presented as a new approach to the problem. They apply knowledge-based techniques to generate a skeleton application in source code which contains the correct program structure and many of the API calls required. This increases productivity and reduces the learning curve whilst retaining all the advantages of development in a standard 3GL.< >
Typical features of windows-based systems are presented. As windowing systems are typically part of a composite GUI (graphical user interface), an overview of a variety of GUIs is provided. Both non-X-Windows and X-Wi...
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Typical features of windows-based systems are presented. As windowing systems are typically part of a composite GUI (graphical user interface), an overview of a variety of GUIs is provided. Both non-X-Windows and X-Windows variants are covered.< >
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