The contour model of block structured processes

ABSTRACT

There appears to be a need for an intuitive implementable cell-based model of the semantics of algorithm execution. It is contended that for block structured processes, such a model must be based on the concepts of nested blocks, access environments, labels, and cell retention. A model so based, the contour model, is introduced by illustrating the execution of an ALGOL 60 program in terms of the model. The model is informally specified and some of its major features are pointed out. A companion paper by D. M. Berry shows that semantically powerful languages can be directly implemented in terms of the model.

REFERENCES

• 1: B1. Barron, D. W. et al., The Main Features of CPL. Comp. J. 6 (1963), 134--143.
• 2: Richard Baumann, Introduction to ALGOL (Prentice-Hall series in automatic computation), Prentice-Hall, Inc., Upper Saddle River, NJ, 1964
• 3: B3. Beech, D., A Structural View of PL/1. IBM Research Rep. RC 2460, Yorktown Heights, 5 May 1969.
• 4: B4. Berry, D. M., Introduction to Oregano. Proceedings of Symp. on Data Structures in Programming Languages, Gainesville, Fla., Feb. 1971.
• 5: C1. Cleary, J. G., Process Handling on the Burroughs B6500. Proc. Fourth Australian Comp. Conf. Adelaide, S. Australia. 1969. pp 231--239.
• 6: D1. Dijkstra, E. W., Recursive Programming. Num. Math. 2 (1960). 312--318.
• 7: H1. Hauck, E. A. and Dent, B. A., Burroughs B6500/B7500 Stack Mechanism. Proc. AFIPS 1968 Spring Joint Comp. Conf., Vol. 32. Thompson, Washington, D. C., pp 245--251.
• 8: H2. Henhapl, W. and Jones, C. B., The Block Concept and Some Possible Implementations, with Proofs of Equivalence. IBM Laboratory, Vienna, Tech. Rep. TR 25.104, 3 April 1970.
• 9: J1. Johnston, J. B., Price, G. B. and VanVleck, F. S., <u>Linear Equations and Matrices</u>. Addison-Wesley, Reading, Mass. 1966.
• 10: J2. Johnston, J. B., Structure of Multiple Activity Algorithms. Proc. Third Ann. Princeton Conf. on Inf. Sci. and Sys. Princeton, March 1969. pp 38--43.
• 11: J3. Johnston, J. B. Ibid. Proc. Second Symposium on Operating Systems Principles. Princeton, October 1969.
• 12: J4. Johnston, J. B. The Contour Model of Block Structured Processes. General Electric Res. and Dev. Ctr. report being written.
• 13: J5. Jorrand, P. and Wegner, P., Some Aspects of the Structure of Basel. Brown Univ., Providence, R. I., January 1970.
• 14: L1. Lucas, P., Lauer, P. and Stigleitner, H., Method and Notation for the Formal Definition of Programming Languages. IBM Laboratory, Vienna, Tech. Rep. TR 25.087, 28 June 1968.
• 15: J. W. Backus , F. L. Bauer , J. Green , C. Katz , J. McCarthy , A. J. Perlis , H. Rutishauser , K. Samelson , B. Vauquois , J. H. Wegstein , A. van Wijngaarden , M. Woodger , P. Naur, Revised report on the algorithm language ALGOL 60, Communications of the ACM, v.6 n.1, p.1-17, Jan. 1963 [doi>10.1145/366193.366201]
• 16: N2. Naur, P. The Design of the GIER ALGOL Compiler. <u>Ann. Rev. in Automatic Programming</u>, Vol. 4. Pergamon Press, New York, 1964, pp 49--85.
• 17: Brian Randall , Lawford J. Russell, Algol-60 Implementation, Academic Press, Inc., Orlando, FL, 1964
• 18: John C. Reynolds, G/EDANKEN—a simple typeless language based on the principle of completeness and the reference concept, Communications of the ACM, v.13 n.5, p.308-319, May 1970 [doi>10.1145/362349.362364]
• 19: Edwin H. Satterthwaite, MUTANT 0.5: an experimental programming language, Stanford University, Stanford, CA, 1969
• 20: C. H Lindsey, Informal introduction to ALGOL 68, sole distributors for the U.S.A. and Canada Elsevier/North-Holland, 1977
• 21: A. van Wijngaarden, Report on the algorithmic language ALGOL 68, Printing by the Mathematisch Centrum, 1969
• 22: Peter. Wegner, Programming Languages, Information Structures, and Machine Organization., McGraw Hill Text, 1968
• 23: W2. Wegner, P. Three Computer Cultures: Computer Technology, Computer Mathematics, and Computer Science. <u>Advances in Computers</u>, Vol. 10. 1970.
• 24: W3. Wegner, P. Information Structure Models for Programming Languages. TR 70-26. Center for Computer and Information Sciences, Brown Univ., September 1970.
• 25: Niklaus Wirth, On certain basic concepts of programming languages, Stanford University, Stanford, CA, 1967
• 26: Niklaus Wirth , Helmut Weber, EULER: a generalization of ALGOL and it formal definition: Part 1, Communications of the ACM, v.9 n.1, p.13-25, Jan. 1966 [doi>10.1145/365153.365162]
• 27: W6. Wozencraft, J. M. and Evans Jr., A., Notes on Programming Linguistics. Dept. Elec. Eng., Mass. Inst. of Tech., Cambridge, Mass., July 1969.