in computation theory, the blum–shub–smale machine, or bss machine, is a model of computation introduced by lenore blum, michael shub and stephen smale, intended to describe computations over the real numbers. essentially, a bss machine is a random access machine with registers that can store arbitrary real numbers and that can compute rational functions over reals in a single time step. it is often referred to as real ram model. bss machines are more powerful than turing machines (which in a sense are restricted to storing rational numbers only).