The execution of a program on a processor is viewed as a representation of that program going through a sequence of states. Each state change is manifested by the execution of a single instruction. Models that depend on this perspective are presented. The first is a static model of a description of a procedural computation. This model formalizes the description of the information in an executable module. Following this dynamic model of a procedural computation is given. This second model describes how a computation transitions from state to state and how the states of a computation are represented. Next, the state of a procedural computation is defined at certain well-defined points in its progression. These points represent potential points of correspondence to another instance of the computation. Then, the equivalence of these well-defined computation states is described. This refinement eliminates the nonmatching potential correspondences. The remaining points describe where the two computations are in the same state. These are precisely the points of equivalence of procedural computations. This final model of pointwise equivalence can be applied to the problem of migrating a computation from one processor to another (possibly architecturally dissimilar) processor.

This paper describes the assembly language course we teach, using a Digital Equipment Corporation VAX-11/780 minicomputer, in which structured programming is stressed. It also discusses the relative merits and disadvantages of choosing the VAX as the computer to be used in such a course.

Many of those who teach introductory computing courses have recognized the pedagogic value of a very simple computer model. A large number of introductory textbooks on computing contain a section explaining the logical components of such a system (1, 2, 3, 4, 5, 6, 7,8). These usually include an introduction to assembler language and machine level programming of a machine which is sometimes called the minimum configuration computer model.