This book addresses issues concerning the engineering of system prod-
ucts that make use of computing technology. These systems may be prod-
ucts in their own right, for example a computer, or they may be the
computerised control systems inside larger products, such as factory
automation systems, transportation systems and vehicles, and personal
appliances such as portable telephones. In using the term engineering
the authors have in mind a development process that operates in an
integrated sequence of steps, employing defined techniques that have
some scientific basis. Furthermore we expect the operation of the stages
to be subject to controls and standards that result in a product fit for
its intended purpose, both in the hands of its users and as a business
venture. Thus the process must take account of a wide range of
requirements relating to function, cost, size, reliabili- ty and so on.
It is more difficult to define the meaning of computing technology.
These days this involves much more than computers and software. For
example, many tasks that might be performed by software running in a
general purpose computer can also be performed directly by the basic
technology used to construct a computer, namely digital hardware.
However, hardware need not always be digital; we live in an analogue
world, hence analogue signals appear on the boundaries of our systems
and it can sometimes be advantageous to allow them to penetrate further.