Storage modification machines

Abstract

In 1970 the author introduced a new machine model (cf. [11]) now called storage modification machine (SMM) and posed the intuitive thesis that (among all models of an atomistic nature) this model possesses extreme flexibility. In the meantime some progress has been made in comparing SMMs with other machine models by investigating the possibility of real time reductions. Here we give a survey of our present knowledge of SMMs. We briefly explain the notion of Δ-structures (which serve as storage devices), the instruction set of an SMM, the related successor RAM model and its real time equivalence to the SMM model. Then we discuss the relationship between SMMs and Kolmogorov Uspenskii machines (KUM) introduced in [7]. In spite of the obvious similarities KUMs are different from SMMs; they are certainly not stronger but perhaps weaker than SMMs.