In
computer science, a
digital electronic computer is a
computer machine which is both an
electronic computer and a
digital computer. Examples of a digital electronic computers include the
IBM PC, the
Apple Macintosh as well as modern
smartphones. When computers that were both
digital and electronic appeared, they displaced almost all other kinds of computers, but
computation has historically been performed in various non-digital and non-electronic ways: the
Lehmer sieve is an example of a digital non-electronic computer, while
analog computers are examples of non-digital computers which can be electronic (with
analog electronics), and
mechanical computers are examples of non-electronic computers (which may be digital or not). An example of a computer which is both non-digital and non-electronic is the ancient
Antikythera mechanism found in
Greece. All kinds of computers, whether they are digital or analog, and electronic or non-electronic, can be
Turing complete if they have sufficient
memory. A digital electronic computer is not necessarily a
programmable computer, a
stored program computer, or a
general purpose computer, since in essence a digital electronic computer can be built for one specific application and be non-reprogrammable. As of 2014, most
personal computers and
smartphones in people's homes that use
multicore central processing units (such as
AMD FX,
Intel Core i7, or the multicore varieties of
ARM-based chips) are also
parallel computers using the
MIMD (multiple instructions - multiple data) paradigm, a technology previously only used in digital electronic
supercomputers. As of 2014, most digital electronic supercomputers are also
cluster computers, a technology that can be used at home in the form of small
Beowulf clusters. Parallel computation is also possible with non-digital or non-electronic computers. An example of a parallel computation system using the
abacus would be a group of
human computers using a number of abacus machines for computation and communicating using
natural language.