ABSTRACT

We investigate the relative strengths of classes of computation models
using the 'While' programming language over many sorted algebras.
We consider the 'While' language with and without counters,
stacks and arrays; and also the language with a limited number
of these constructs.  Among the results we show are:

* 'While' with 1 stack is incomparable with 'While' with counters;

* 'While' with 2 counters (only) is as strong as 'While' with arbitrarily 
   many counters;  but

* 'While' with 1 counter (only) is no stronger than 'While' without counters.