  This paper presents an algebraic theory of instruction sequences with
instructions for a random access machine (RAM) as basic instructions, the
behaviours produced by the instruction sequences concerned under execution, and
the interaction between such behaviours and RAM memories. This theory provides
a setting for the development of theory in areas such as computational
complexity and analysis of algorithms that distinguishes itself by offering the
possibility of equational reasoning to establish whether an instruction
sequence computes a given function and being more general than the setting
provided by any known version of the RAM model of computation. In this setting,
a semi-realistic version of the RAM model of computation and a bit-oriented
time complexity measure for this version are introduced. Under the time measure
concerned, semi-realistic RAMs can be simulated by multi-tape Turing machines
with quadratic time overhead.
