The programming language ALGOL 68 offers great flexibility in the use of modes and operators. The convenience for the programmer results in problems for the implementor in coercion, balancing, and identification of operators. This thesis presents a solution to these problems that is being successfully used in an ALGOL 68 compiler. / Science, Faculty of / Computer Science, Department of / Graduate

The special feature that modes and operators can be defined by the user of ALGOL 68 has induced the problems of coercion, balancing and operator identification. This work deals with the mode manipulation and operator identification in ALGOL 68. The algorithms are based on those of [Z]. Some of the revisions to the ALGOL 68 Report concerning modes, such as no proceduring, the void symbol, the definition of NONPROC, the definition of a vacuum, and the hipping of a vacuum are included. The program in ALGOL W is based on that of [P]. The program described in this thesis does four main jobs: mode eguivalencing, mode coercion, mode balancing and operator identification. In mode eguivalencing, it checks the context conditions concerning "showing" [R.4.4.4] and the multiple occurrence of the same field selector in a structure [R.4.4.3e], and checks related modes in unions [ B.4.4.3b,d]. In mode coercion, it determines the coercion steps. This is also a basic part of mode balancing and operator identification. In balancing, it also considers collateral displays. This is a model for the operator identification part of an ALGOL 68 compiler. I am deeply indebted to Professor J. E. L. Peck for initiating my study of ALGOL 68 and ALGOL W, for suggesting the topic of this thesis and for rendering invaluable assistance, encouragement and patience throughout the course of my work. I would like to thank the group which is working under Dr. Peck for the ALGOL 68 implementation, Dr. W. J. Hansen and especially Dr. M. Zosel for many helpful suggestions and discussions. I gratefully acknowledge the financial support of NRC. / Science, Faculty of / Computer Science, Department of / Graduate

A system for the Input, retrieval, display, and overlay of 2-dimensional geographical data sets has been developed. The Geographical Information and Display System (GIDS) has been designed according to the following criteria: the system should be easy to use, easy to evolve, problem-independent, interactive, and graphic-oriented. Thematic map data are encoded by locational data elements (points, lines, or polygons) over which some attribute is homogeneous. Both the attribute and locational data are then input to GIDS and stored in sequential file structures, from which they can be selectively retrieved, displayed, and manipulated at user request. All user requests to the system may be expressed interactively via an English-like command language. Each command, corresponding to one operation such as input, display or overlay, is interpreted and executed by an independent module which accesses the data through a common input/output framework. GIDS has proved useful to planners and researchers because of Its ability to display and relate data from different maps. / Science, Faculty of / Computer Science, Department of / Graduate

An implementation of the programming language Logo is described. Logo, a programming language somewhat like Lisp, is intended to teach the naive user the elements of programming and problem-solving, especially in symbolic programming applications such as graphics, natural language processing, musical composition, and the solution of elementary artificial intelligence problems. The system described here, BCLogo, is an attempt to build a portable implementation which would net be particularly sensitive to the computer on which it was run. The thesis describes both the manner in which the system appears to the user and the way in which the system was built. / Science, Faculty of / Computer Science, Department of / Graduate

The purpose of this thesis is to report on the study, implementation arad use of the LR (k) parsing technique with error recovery as applied to the computer programming language ALGOL 68. The LR (k) parsing technique is a powerful method of automatic construction of parsers for context free grammars. The methodology provided by De Remer is implemented for all classes of LR (k) grammars. The practical implementation of the translator limits k to 15. The necessity of having error recovery for any parsing technique cannot be overstated. An error recovery technique is provided and demonstrated for ALGOL 68. This technique uses the parsing translator to aid in the decision process to determine the transformation from a string of symbols not in the language, to a string of symbols in the language. The LR (k) parsing technique and the error recovery technique are applied to ALGOL 68 and prove to be practical techniques in the construction of compilers for computer programming languages. / Science, Faculty of / Computer Science, Department of / Graduate

The design of large-scale industrial or experimental facilities oftentimes involves the routing of complex networks of power supply lines, control lines or signals, heating or cooling ducts, product transmission pipes etc. In such cases it is essential to be able to maintain an up-to-date, easily accessible, global record of each cable, duct or signal path, the function each performs and its relation to like elements within the system. It is the purpose of this thesis to describe such a facility as implemented by a conversational computer program - SYSREC. The facility discussed allows the user to build network configurations, perform minimum path routing of signals etc., delete connectors or signals and save the record of a network for further modification at some later date. In addition, it is possible to generate output summarizing, in detail, the status of a given network. The program is designed to perform the above operations interactively by means of commands inputted by the user. The thesis is composed of two logically separate sections; a User's Manual describing the capabilities and usage of the program and a Logic Manual describing the internal logic of the program. The purpose of such a separation is to provide self contained references for two distinct levels of user: the general user and the user who wishes to extend or modify the existing implementation. Since both the User's Manual and the Logic Manual contain their own tables of contents, appendices etc., the thesis may be split into two physically distinct parts should the need arise. / Science, Faculty of / Computer Science, Department of / Graduate

An implementation of a Lisp Library is described. This Library provides a simple and uniform scheme for programmer access to a number of Lisp support programs. A scheme by which programs are automatically loaded from this Library is presented, as well as methods of querying the system and unloading selected programs. A facility for aiding in the debugging of Lisp programs is also described. / Science, Faculty of / Computer Science, Department of / Graduate

An interactive system is described which allows for the graphic construction, simulation, and simultaneous animation of an arbitrary network of queues. A method is proposed and implemented for representing the events of a discrete simulation by a continuous animation on a graphics terminal. Techniques are presented for the display of parallel animation "sequences," and a non-trival mapping of simulation time into animation time is described which preserves the relative order and time relationships between events. The program implemented combines this animation facility with other simulation monitoring and control features. The usefulness of this type of approach is discussed with respect to computer-aided design applications, educational tools, and research tools. An interactive dialogue which makes use of the lightpen and a menu of commands is implemented for the construction and modification of the queuing network. Certain relevent aspects of man-machine interaction are discussed. Also, some prospects are considered for applying the animation techniques developed in this implementation to other discrete event processes. / Science, Faculty of / Computer Science, Department of / Graduate

This thesis describes the design of a system that converts the intermediate language SLIM, into assembler code for the Motorola MC68000. This is then assembled and loaded onto a MC68000 simulator where it successfully runs. The suitability of SLIM as an intermediate language is also studied, with a treatment on code optimization. / Science, Faculty of / Computer Science, Department of / Graduate

This thesis discusses the design and implementation of the computer language SLING (Structured Language for Interactive Graphics). SLING by assign is a high-level structured procedural language. Constructs promoting user interaction have been added to enhance graphics capabilities. The implementation of SLING is core and execution-time efficient relative to current computer graphics languages. It is designed to run on a minicomputer with minimal core requirements. / Graduate and Postdoctoral Studies / Graduate