Function is limited so as to prevent exploitation of Turing
capability or similar expansion of intended function. Examples include
limited function interfaces to systems, special purpose devices which
perform only specific functions dictated by their designers, and special
devices designed to fail under attempts to use them for other than their
Complexity: It has been shown that systems with even a very limited set of
functions can be used to implement general purpose systems.
For example, NOR gates can be used to create ANY digital
electronic function, and, subject to tolerance requirements, general purpose
physical machines also exist.