Programming language subsets

Status:

completed 12/2000

Aims:

In recent years, computer systems have gained increasing importance in safety-related control systems. The software has a major influence upon the safety of machinery and protective equipment in this respect. Complex sequence control is increasingly being performed exclusively by software, the tasks performed by hardware being relegated to the background. Over the past ten years, the BG Institute for Occupational Safety (BIA) has, in the course of a number of studies into the principles of programmable electronic control and safety systems, gathered experience in the area of safety software. These studies all indicate that the style of programming has a decisive influence upon the facility for maintenance and testing of control software. Since few studies are currently being performed into the use of programming languages in safety technology, the project is of major importance for current safety technology.

Activities/Methods:

Literature surveys and individual analyses were performed to define language concepts, strengths and weaknesses and limits of the language subsets of the programming languages ADA, BASIC, C, C++, FORTRAN, MODULA-2 and PASCAL, and assembler. Following a study into the general aspects of programming and of individual programming languages, general rules were first drawn up for programming. Specific rules were then drawn up for each of the above programming languages, together with the reasons for them. Information gained from the literature and from day-to-day experience was incorporated here into the guideline. Some controller manufacturers have already employed these rules in work on current projects.

Results:

Rules for the use of programming languages in safety applications were drawn up for ADA, C, C++, FORTRAN, MODULA-2, PASCAL and BASIC, and for assembler. These rules were published both in book form and as articles in periodicals. The rules are categorized according to the semantics of the respective programming languages, and contain numerous examples for practical implementation. In addition to the rules specific to each language, the publications contain general rules for the programming of safety-related applications. The publication represents the first example of a comprehensive work on this subject.

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