Interfaces in Computing最新文献

A distributed processing system based on UNIX (trademark of Bell Laboratories) is currently operational at New Mexico State University. The system which is composed of a variety of PDP-11 and LSI-11 processing elements allows users to schedule tasks to run totally or in parallel on its satellite units. A UNIX-like kernel is run on the satellite processors and this allows virtually any process to run on any processing element. The architecture of the system is a star configuration with a PDP-11/34a as the central or host node. To support experiments in parallel processing, a parallel version of the C programming language has been developed which allows users to write programs as a collection of functional units which can be automatically scheduled to run on the satellite processors. In this paper the structure of the system is described in terms of hardware and software, and our implementation of pc, a parallel C language, is discussed.

A general purpose, low cost and flexible system for multichannel data acquisition is described. The system uses the general purpose interface bus (GPIB) as a back plane in an instrument crate into which specially developed GPIB instruments can be inserted as modules. The crate concept represents an extension to the GPIB standard, and it reduces drastically the cost of programmable instrument systems, while still maintaining the generality of the GPIB. Descriptions of three programmable GPIB modules designed for the system illustrate its possibilities.

An architecture of a database system for non-expert users and capable of supporting manual document structures is described. The development of a user-oriented data model (UODM) with suitable constructs is presented. Various design strategies for generating an appropriate relational schema automatically from the UODM are presented and discussed. Finally it is pointed out that the use of a typifying attribute and a set of mutually exclusive attributes may be of use as a general data analysis tool.

A description of the design of a database system based on the entity relationship model is given with particular reference to the data storage subsystem.

The setting-up of a database project at Manchester University is described together with the initial implementation of the database system which evolved from it. The criteria for the choice of the data model to be used are discussed and four data models are considered. The reasons behind the final choice of the entity relationship model are given.

A description of and the reasons for the modular design of the system are presented. The structure of the data storage subsystem is described and two data storage models are discussed.

Details of the database system's data access primitives are supplied together with a description of the mechanisms used to implement them.

In this paper the important issues to be considered in the effective use of a microcomputer as a teaching aid in schools are identified. The goals of the secondary school English teacher are considered in the context of using a microcomputer to aid the teaching of basic literacy skills. Particular attention is paid to the role of dialogue description software in the implementation and development strategy for the material.

Although work towards international standards for computer graphics was started in 1976, it is in the last 2 years that real agreement and progress have been achieved. The first target, the functional specification of a graphics system, is satisfied by the graphical kernel system (GKS), which is now being processed as an International Organization for Standardization (ISO) draft international standard. GKS provides a reference model for two-dimensional graphics and an agreed vocabulary of terms covering the field. Many implementations of GKS as a package are now being produced. In addition to such a functional specification, two forms of communication are appropriate for graphics: a metafile and a virtual device interface. ISO is now reviewing a proposal for a metafile standard developed by the American National Standards Institute and closely related to GKS. Standards for a graphics virtual device interface and for three-dimensional graphics systems are also being actively developed. All these efforts and their interrelationships are described and examined.