Control Structures for Programming Languages

. The research reported here is the result of an investigation of several aspects of the control structure of programming languages. By control structures we mean _ • programming environments or operations which specify the sequencing and interpretation rules for programs or parts of programs. This dissertation attempts to demonstrate the thesis: complexity diminishes and clarity increases to a marked degree if algorithms are described in a language in which appropriate control structures are primitive or easily expressible. A number of •control structures extant in programming languages and systems are catalogued and then used as a guide to develop a programming language which has a control extension "_ facility. This language has not only the mechanical necessities for control extensions, but also has primitive control operations for sequential processing, parallel processing, alternative selection, monitoring, synchronization, ° and relative continuity. These operations are the source of the clarity of control descriptions because they span ou_ conceptual notion of control and because they can be easily composed to form other more specialized control structures.