  A parameterized algebraic theory of instruction sequences, objects that
represent the behaviours produced by instruction sequences under execution, and
objects that represent the behaviours exhibited by the components of the
execution environment of instruction sequences is the basis of a line of
research in which issues relating to a wide variety of subjects from computer
science have been rigorously investigated thinking in terms of instruction
sequences. In various papers that belong to this line of research, use is made
of an instantiation of this theory in which the basic instructions are
instructions to read out and alter the content of Boolean registers and the
components of the execution environment are Boolean registers. In this paper,
we give a simplified presentation of the most general such instantiated theory.
