摘要:

AbstractPIC is a language for specifying pictures so that they can be typeset as an integral part of a document preparation system. The basic objects in PIC are boxes, lines, arrows, circles, ellipses, arcs and splines, which may be placed at positions specified absolutely or in terms of previous objects, and labeled with arbitrary text. The example below illustrates the general capabilities of the language.Most of the effort in designing PIC has gone into making it possible to specify the sizes and positions of objects with minimal use of absolute coordinates.This paper describes PIC, with primary emphasis on those aspects of the language that make it easy to use. The paper was typeset using PIC.

ISSN:0038-0644    

DOI:10.1002/spe.4380120102

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractBacktrack algorithms are applicable to a wide variety of problems. An efficient but readable version of such an algorithm is presented and its use in the problem of finding the maximal common subgraph of two graphs is described. Techniques available in this application area for ordering and pruning the backtrack search are discussed. This algorithm has been used successfully as a component of a program for analysing chemical reactions and enumerating the bond changes which have taken place.

ISSN:0038-0644    

DOI:10.1002/spe.4380120103

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper studies the use of text signatures in string searching. Text signatures are a coded representation of a unit of text formed by hashing substrings into bit positions which are, in turn, set to one. Then instead of searching an entire line of text exhaustively, the text signature may be examined first to determine if complete processing is warranted. A hashing function which minimizes the number of collisions in a signature is described. Experimental results for two signature lengths with both a text file and a program file are given. Analyses of the results and the utility and application of the method conclude the discussion.

ISSN:0038-0644    

DOI:10.1002/spe.4380120104

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper describes the transportation of sequential and concurrent Pascal from the SOLO distribution tape to a non‐PDP‐11 like mainframe (IBM 370/145). An interpreter for the idealized virtual machine was written in FORTRAN. Subsequently the PDP‐11 dependencies were removed from the interpreter and compilers so that a more transportable version of concurrent Pascal could be generated. A FORTRAN system was then constructed which simulated an operating system environment in which the interpreter could run. Clock and device interrupts are simulated so that process scheduling can be undertaken as if real interrupts were being generated.The system was constructed for a teaching environment so that several students could make use of the Polytechnic's interactive computer system each running their own concurrent s

ISSN:0038-0644    

DOI:10.1002/spe.4380120105

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThree string matching algorithms—straightforward, Knuth‐Morris‐Pratt and Boyer‐Moor—re examined and their time complexities discussed. A comparison of their actual average behaviour is made, based on empirical data presented. It is shown that the Boyel‐Moore algorithm is extremely efficient in most cases and that, contrary to the impression one might get from the analytical results, the Knuth‐Morris‐Pratt algorithm is not significantly better on the average than the straightfo

ISSN:0038-0644    

DOI:10.1002/spe.4380120106

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractVarious qualities of simple command languages, such as ease of use and flexibility, are defined in terms of syntax. Certain design attributes—namely style, structure and level of abstraction—are described for command languages, and these attributes are shown to strongly influence the defined qualities. Commands are designed for three functions to show how the design trade‐offs are made in light of the qualities and attributes disc

ISSN:0038-0644    

DOI:10.1002/spe.4380120107

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper proposes some improvements to the archaic methodologies currently used for checkout of real‐time software. The emphasis is placed on removing errors from the computer program source code in the host computer environment, and deferring target computer checkout until those errors have been largely removed. Specific tools and techniques to make this possible are described. This improvement is seen to be risk‐free and to reduce cost. It is, however, controvers

ISSN:0038-0644    

DOI:10.1002/spe.4380120108

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractAn implementation of Concurrent Pascal on a UNIVAC1106 is described. Design decisions include the choice of compiled rather than interpreted code, as well as scheduling strategies. The advantages and disadvantages of a mainframe implementation are discussed.

ISSN:0038-0644    

DOI:10.1002/spe.4380120109

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThis paper describes a simple experiment concerning the quality of error messages for a syntax error in Pascal.

ISSN:0038-0644    

DOI:10.1002/spe.4380120110

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY

摘要:

AbstractThis communication provides performance measurements for message‐passing between LSI11/03s via a Cambridge Ring. The figures show interrupt‐driven Ring access to be intolerably s

ISSN:0038-0644    

DOI:10.1002/spe.4380120111

出版商:John Wiley&Sons, Ltd.    

年代:1982

数据来源: WILEY