Inter-program communications, program string structures

INTRODUCTION Receptiveness to change is one of the most important attributes of a programming system. There are obvious advantages associated with being responsive to changes in a system's environment without being required to essentially redesign the system. These environmental changes may take the form of variations in the functions to be performed by the system or in the applications to which the system is put. They may be reflected in modifications of the content or structure of the data which the system is to process. They may even appear as changes in the number, type or function of the equipments comprising the computer within which the system is operated. The introduction of program modularity is one of the most common approaches to designing programming systems capable of evolutionary growth and modernization. Traditionally, modularity is associated with the division of a program system into its major components, which in turn are divided into their subcomponents, and so on. The degree to which this can be actually reduced to practice, however, is a function of the facilities available for combining the program modules into larger programs. Factors which must be considered are the extent to which inter-program dependencies exist, the nature of the mechanism available for resolving such dependencies, and the time at which they are resolved. If the program modules could be treated as completely separate entities, wholly independent of one another, they could be used as program building blocks to be arbitrarily combined to form larger programs. This generalization leads to the notion of a pool in which all program building blocks are maintained, available for use in larger programs to perform user-oriented functions. The application of Program String Structure techniques l allows such a generalization to be made, and hence allows for the realization of the notion of a program building block pool. The most essential feature of the Program String Structure concept is the introduction of Buffer Files