In computer science, a digital electronic computer is a computer machine which is both an electronic computer and a digital computer. Examples of digital electronic computers include the IBM PC, the Apple Macintosh, and 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. , 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 instruction, multiple data) paradigm, a technology previously only used in digital electronic supercomputers. , 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. A digital computer can perform its operations in the decimal system, in binary, in ternary or in other numeral systems. , all digital electronic computers commonly used, whether personal computers or server computers or supercomputers, are working in the binary number system and also use binary logic. A few ternary computers using ternary logic were built mainly in the Soviet Union as research projects. A digital electronic computer is not necessarily a transistorized computer: before the advent of the transistor, computers used vacuum tubes. The transistor enabled electronic computers to become much more powerful, and recent and future developments in digital electronics may