publisher atom 
A microcomputer is a small , relatively inexpensive computer with a microprocessor as its central processing unit ( CPU ). It includes a microprocessor , memory , and minimal input / output ( I / O ) circuitry mounted on a single printed circuit board . Microcomputers became popular in the 1970s and 1980s with the advent of increasingly powerful microprocessors . The predecessors to these computers , mainframes and minicomputers , were comparatively much larger and more expensive ( though indeed present - day mainframes such as the ___MASK98___ System z machines use one or more custom microprocessors as their CPUs ). Many microcomputers ( when equipped with a keyboard and screen for input and output ) are also personal computers ( in the generic sense ). Dark matter is an unidentified type of matter distinct from dark energy , baryonic matter ( ordinary matter ), and neutrinos . The name refers to the fact that it does not emit or interact with electromagnetic radiation , such as light , and is thus invisible to the entire electromagnetic ___MASK99___ . Although dark matter has not been directly observed , its existence and properties are inferred from its gravitational effects such as the motions of visible matter , gravitational lensing , its influence on the universe ' s large - scale structure , on galaxies , and its effects in the cosmic microwave background . Hydrogen is a chemical element with chemical symbol H and atomic number 1 . With an atomic weight of , hydrogen is the lightest element on the periodic table . Its monatomic form ( H ) is the most abundant chemical substance in the Universe , constituting roughly 75 % of all baryonic mass . Non - remnant stars are mainly composed of hydrogen in the plasma state . The most common isotope of hydrogen , termed " protium " ( name rarely used , symbol H ), has one proton and no neutrons . The Universe is all of time and space and its contents . It includes planets , moons , minor planets , stars , galaxies , the contents of intergalactic space , and all matter and energy . The size of the entire Universe is ___MASK20___ . ___MASK13___ , was an American family - owned leather goods company based in Fort Worth , Texas . Tandy Leather was founded in 1919 as a leather supply store , and acquired a number of craft retail companies , including RadioShack in 1963 . In 2000 , the ___MASK13___ name was dropped and entity became the RadioShack Corporation . The TRS - 80 Micro Computer System ( TRS - 80 ; later known as the Model I to distinguish it from successors ) is a desktop microcomputer launched in 1977 and sold by ___MASK13___ through their Radio Shack stores . The name is an abbreviation of " Tandy / Radio Shack , Z - 80 microprocessor ". It was one of the earliest mass - produced personal computers . Weakly interacting massive particles ( WIMPs ) are hypothetical particles that are thought to constitute dark matter . There exists no clear ___MASK93___ of a WIMP , but broadly a WIMP is a new elementary particle which interacts via gravity and any other force ( or forces ), potentially not part of the standard model itself , which is as weak as or weaker than the weak nuclear force , but also non - vanishing in its strength . A WIMP must also have been produced thermally in the early Universe , similarly to the particles of the standard model according to Big Bang cosmology , and usually will constitute cold dark matter . Obtaining the correct abundance of dark matter today via thermal production requires a self - annihilation cross section of formula_1 , which is roughly what is expected for a new particle in the 100 GeV mass range that interacts via the electroweak force . Because supersymmetric extensions of the standard model of particle physics readily predict a new particle with these properties , this apparent coincidence is known as the  WIMP miracle , and a stable supersymmetric partner has long been a prime WIMP candidate . However , recent null results from direct detection experiments including LUX and SuperCDMS , along with the failure to produce evidence of supersymmetry in the Large Hadron Collider ( LHC ) experiment has cast doubt on the simplest WIMP hypothesis . Experimental efforts to detect WIMPs include the search for products of WIMP annihilation , including gamma rays , neutrinos and cosmic rays in nearby galaxies and galaxy clusters ; direct detection experiments designed to measure the collision of WIMPs with nuclei in the laboratory , as well as attempts to directly produce WIMPs in colliders , such as the LHC . The XENON dark matter research project operated at the Italian Gran Sasso laboratory is a deep underground research facility featuring increasingly ambitious experiments aiming to finally detect long sought after dark matter particles . These particles in the form of Weakly interacting massive particles ( WIMPs ) are believed to be found by looking for ___MASK63___ interactions via nuclear recoils in a liquid xenon target chamber . The current detector consists of a dual phase Time projection chamber ( TPC ). Atom is a home computer game published by Tandy in 1983 for the TRS - 80 . The game educates the player about the first few elements of the periodic table ( Hydrogen through Xenon ) .