A simple system for constructing distributed,mixed-language programs

The Mixed-Language Programming (MLP) System is a simple system that facilitates construction of sequential programs in which procedures can be written in different programming languages to exploit heterogeneity in language functionality. In addition, MLP provides a simple remote procedure call (RPC) facility that allows heterogeneity in machine functionality to be exploited. To minimize implementation cost, the system does not solve all of the problems related to mixed-language programming; rather, MLP is designed to handle common situations well. Among the unique aspects of MLP are its advanced facilities, which allow complex situations to be handled with user intervention; for example, these facilities allow arguments of a type not defined by a language to be used by procedures written in that language. This paper overviews the use of MLP and describes its implementation. In addition, two programs that have been written using the MLP system—a small database system and a collection of plot routines—are discussed. The system executes on a collection of Vaxes and Suns running Berkeley UNIX. Currently supported languages are C, Pascal and Icon.     

DFL: A Data Flow Language

Many novel computer architectures like array and multiprocessors which achieve high performance through the use of concurrency exploit variations of the von Neumann model of computation. The effective utilization of the machines makes special demands on programmers and their programming languages, such as the structuring of data into vectors or the partitioning of programs into concurrent processes. In comparison, the data flow model of computation demands only that the principle of structured programming be followed. A data flow program, often represented as a data flow graph, is a program that expresses a computation by indicating the data dependencies among operators. A data flow computer is a machine designed to take advantage of concurrency in data flow graphs by executing data independent operations in parallel. In this paper, we discuss the design of a high level language (DFL: Data Flow Language) suitable for data flow computers. Some sample procedures in DFL are presented. The implementation aspects have not been discussed in detail since there are no new problems encountered. The language DFL embodies the concepts of functional programming, but in appearance closely resembles Pascal. The language is a better vehicle than the data flow graph for expressing a parallel algorithm. The compiler has been implemented on a DEC 1090 system in Pascal.     

The design of an interactive program development system for Pascal

A program language can be defined as the language in which computer programs are written, and a programming language as the language used by the programmer to create programs. This paper presents the design of an interactive program development system which uses Pascal as both program and programming language. Principal properties of the system are a complete immediate syntax check, a program-structure oriented editor, incremental compiling techniques, and interactive interpretation and debugging of programs. The syntax check is split into three phases, and the user can change the degree of check wanted. After a change of the program only part of it is recompiled, and only necessary phases of the compiling process are performed.     

An analysis of Pascal programs in compiler writing

A method and results of static and dynamic analysis of Pascal programs are described. In order to investigate characteristics of large systems programs developed by the stepwise refinement programming approach and written in Pascal, several Pascal compilers written in Pascal were analysed from both static and dynamic points of view. As a main conclusion, procedures play an important role in the stepwise refinement approach and implementors of a compiler and designers of high level language machines for Pascal-like languages should pay careful attention to this point. The set data structure is one of the characteristics of the Pascal language and statistics of set operations are also described.     

Language design for program manipulation

The design of procedural and object-oriented programming languages is considered with respect to how easily programs written in those languages can be formally manipulated. Current procedural languages such as Pascal, Modula-2 and Ada; generally support such program manipulations, except for some annoying anomalies and special cases. Three main areas of language design are identified as being of concern from a manipulation viewpoint: the interface between concrete and abstract syntax; the relationship between the abstract syntax and static semantics naming, scoping and typing; and the ability to express basic transformations (folding and unfolding). Design principles are suggested so that the problems identified for current languages can be avoided in the future     

基于HTML语言的跨平台界面设计

描述了如何利用HTML超文本标识语言为终端用户创建基于表单的图形化界面。在这里HTML语言仅用于描述用户界面的的外观，程序的编程可以用许多种编程语言或脚本语言。     

An abstract programming language and correctness proofs

The realization of an abstract programming language is a good approach for automating the software production process and facilitating the correctness proof of a software system.

This paper introduces a formal language for programming at the abstract level by combining Pascal with VDM (Vienna Development Method). The notation provided by the language obliges programmers to consider the correctness of programs throughout the whole process of programming, and the proof axiom and rules presented in this paper may be used to prove the correctness of programs. A complete example is given to illustrate how to program using APL and how to prove the correctness of programs using the given axiom and rules.     

Incremental semantic evaluation in language-based editors

We present an incremental semantic analysis strategy for use in language-based editors. Its advantage is the low storage cost involved in achieving incremental semantic operation with a relatively small loss in response. The scheme, which involves limiting identifier attribute flow, is first described for a simple block-structured language like Pascal, and then extended to more modern modular languages.     

Mixed language programming

Subroutines for numerical computation have in the past been written mainly in Fortran and in Algol 60, whereas most programming in the future is expected to be in more advanced languages, for example in Ada. It seems to be a great waste if it will become necessary to convert all existing numerical software into the new languages. What is needed is a facility to include subroutines written in the old languages into programs being written in the newer languages. In this paper an automatic procedure to facilitate the use of mixed languages is suggested, the purpose of the paper is to indicate the desirability for providing the required facilities, and to encourage discussion and further research in the area of mixed language programming.     

Unisex: A unix-based symbolic executor for pascal

UNISEX is a UNIX-based symbolic executor for Pascal. The UNISEX system provides an environment for both testing and formally verifying Pascal programs. The system supports a large subset of Pascal, runs on UNIX and provides the user with a variety of debugging features to help in the difficult task of program validation. This paper contains a brief introduction to symbolic execution, followed by an overview of the features of UNISEX, a discussion of the UNISEX Pascal language, and some of the implementation details for the UNISEX system. Finally, some of the problems encountered when designing and implementing the system are discussed as well as future directions.     

Process administration in a high level language

The traditional approach to the implementation of process administration in multiprogrammed systems is to make it part of the run-time system or ‘kernel’. This implies first, that the implementation is written in assembler language, and secondly that the process administration will be very inflexible. This article outlines a high level language PoMP, a Pascal extension. Following the trend set by Concurrent Pascal and Modula towards integrating ever increasing parts of the ‘kernel’ in the individual application program, PoMP provides language constructs for implementing process administration. It is shown that the multiprogramming language constructs of a number of languages may be ‘imitated’ in PoMP.     

Translating VDM specifications into ABC programs

Declarative languages such as Miranda and Prolog have often been used to prototype specifications written in the formal notation of VDM, but they have no destructive assignment commands thus making it difficult to model VDM state changes. Imperative languages like C and Pascal allow state changes to be modelled naturally but lack the expressive power to make prototyping feasible. ABC, on the other hand, is a simple yet very powerful imperative language that has a great expressive power making it suitable as a prototyping language. This paper describes the process of translating VDM specifications into ABC programs.     

The trio operating system

This paper is an overview of the Trio system which enables users to simultaneously develop and execute programs at three terminals. The system consists of an operating system written in Concurrent Pascal and a set of standard programs written in Sequential Pascal. The system has been used on a PDP 11/55 minicomputer since spring 1979. This work concludes 5 years of experience with the first abstract language for concurrent programming.     

Message passing communication versus procedure call communication

Communication by message passing or by procedure calls in one of the key issues when discussing languages for multiprogramming. The two languages Platon and Concurrent Pascal represent the different approaches which are contrasted by presenting a few programs written in both languages.     

A Model for Representing Programs Using Hierarchical Graphs

In this paper a hierarchical graph model for programs based on the concepts of recursive graphs (RG's) and Codd relations is presented. The purpose of the model is to clearly represent the structure of a program implemented in a structured language, such as Pascal, Algol, or PL/1, so that the program can be analyzed and modifications to the program can be clearly specified. The model uses an RG representation for the control flow and the data flow with an equivalent relational representation. It also has a relational representation for the objects defmed within the program. The various aspects of the model are illustrated using Pascal constructs and a model for an example Pascal program is given.     

Computer system simulation in Pascal

The programming language Pascal is considered as one of the most interesting computer system simulation tools. This paper discusses design facilities required in simulation languages, making use of a model described in Pascal. An important area is seen to be that of queues, lists or sets, and the facilities that are powerful yet simple to use are stressed. The problem of parallelism and synchronization in a simulator is solved. The structure of the simulator is considered.     

Modular programming with Pascal

A technique is presented by which the programming language Pascal as defined by the expected standard, can be used to write programs divided into modules containing mutually hidden information. The technique fits nicely with the programming by stepwise refinement methodology, combines top-down and bottom-up methods, and illustrates that stepwise refinement does not necessarily lead to simple tree-like programs. Limitations for the application of the technique with Pascal are pointed out.     

Compiler Optimization Correctness by Temporal Logic

Rewrite rules with side conditions can elegantly express many classical compiler optimizations for imperative programming languages. In this paper, programs are written in an intermediate language and transformation-enabling side conditions are specified in a temporal logic suitable for describing program data flow.The purpose of this paper is to show how such transformations may be proven correct. Our methodology is illustrated by three familiar optimizations: dead code elimination, constant folding, and code motion. A transformation is correct if whenever it can be applied to a program, the original and transformed programs are semantically equivalent, i.e., they compute the same input-output function. The proofs of semantic equivalence inductively show that a transformation-specific bisimulation relation holds between the original and transformed program computations.     

The construct of a high-level computer language for programmable assembly

In recent years, considerable effort has been devoted to developing and extending programming languages for manipulation of computer-controlled robotic arms for various tasks. The present trend is to develop high-level languages that simplify the programming task so that they can be used by a less well-trained person with ease and speed. In this article, the information required for assembly is examined and a construct of a new computer language is proposed. An example of a computer program using the proposed language for assembling a pencil sharpener is given. This program is compared with similar program written in another language currently being developed and extended.