A generalized control structure and its formal definition

ABSTRACT

A new programming language control structure as well as an improved approach to a formal definition of programming languages are presented. The control structure can replace both iteration and conditional structures. Because it is a semantic generalization of those structures, a single statement using the new control structure can implement the functions of loops, conditionals, and also programs that would require several conventional constructs. As a consequence of this increased capability, it is possible to write algorithms that are simpler, more efficient, and more clearly correct than those that can be written with earlier structured-programming control structures. In order to provide a precise definition of the new constructs, a new version of relational semantics, called LD-relations is presented. An algebra of these relations is developed and used to define the meaning of the new constructs. A short discussion of program development and the history of control structures is included.

REFERENCES

• 1: ACM statement on ADA. Comm. ACM 25, 2 (Feb. 1982),
• 2: de Bruijn, N.G. Private communication.
• 3: Edsger Wybe Dijkstra, A Discipline of Programming, Prentice Hall PTR, Upper Saddle River, NJ, 1997
• 4: Forthofer, M.J. Extending PDL to include a search superstructure. Tech. Rept. FSD 81-0010, Federal Systems Div., IBM Corp., Bethesda, Md., Apr. 1981.
• 5: David Gries, The Science of Programming, Springer-Verlag New York, Inc., Secaucus, NJ, 1987
• 6: Richard C. Linger , Bernard I. Witt , H. D. Mills, Structured Programming; Theory and Practice the Systems Programming Series, Addison-Wesley Longman Publishing Co., Inc., Boston, MA, 1979
• 7: Roy Alejandro Maddux, A study of computer program structure., 1975
• 8: Mills, H.D. Functional semantics for sequential programs. Prec. IFIP 1980, North-Holland, Amsterdam.
• 9: Harlan D. Mills, The new math of computer programming, Communications of the ACM, v.18 n.1, p.43-48, Jan. 1975 [doi>10.1145/360569.360659]
• 10: Parnas, D.L An alternative control structure and its formal definition. IBM Tech. Rept. TR FSD-81-0012, IBM Corp., Bethesda, Md, 1981.
• 11: Donald F. Stanat , David F. McAllister, Discrete Mathematics in Computer Science, Prentice Hall Professional Technical Reference, 1977

INDEX TERMS

Primary Classification:
  D. Software

Additional Classification:
  D. Software
  D.3 PROGRAMMING LANGUAGES
      D.3.3 Language Constructs and Features
          Subjects: Control structures

  F. Theory of Computation
  F.3 LOGICS AND MEANINGS OF PROGRAMS
      F.3.2 Semantics of Programming Languages
          Subjects: Algebraic approaches to semantics