ion and Store Shapes . . . . . . . . . . 6 2 Two Variations on Algol 8 2.1 Idealized Algol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Name: P.W. O'Hearn Address: Department of Computer Science, Queen Mary and Westfield College, London E1 4NS, UK. e-mail: ohearn@dcs.qmw.ac.uk Name: J.C. Reynolds Address: School of Computer Science, Carnegie Mellon University, Pittsburgh PA 15213-3891, USA. e-mail: john.reynolds@cs.cmu.edu Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or direct commercial advantage and that copies show this notice on the first page or initial screen of a display along with the full citation. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any component of th...

We study a typing scheme derived from a semantic situation where a single category possesses several closed structures, corresponding to dierent varieties of function type. In this scheme typing contexts are trees built from two (or more) binary combining operations, or in short, bunches. Bunched typing and its logical counterpart, bunched implications, have arisen in joint work of the author and David Pym. The present paper gives a basic account of the type system, and then focusses on concrete models that illustrate how it may be understood in terms of resource access and sharing. The most

This note is a historical survey of Christopher Strachey's influence on the development of semantic models of assignment and storage management in procedural languages.