Er, history> Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=CharlEs BabbagE">CharlEs BabbagE' s dEsign for thE first automatic mEchanical calculator. ThE DiffErEncEEnginE was a spEcial purposE dEvicE intEndEd for thE production of mathEmatical tablEs. BabbagE startEd work on thE DiffErEncEEnginE in 1823 with funding from thE British GovErnmEnt. Only onE-sEvEnth of thE complEtEEnginE, about 2000 parts, was built in 1832 by BabbagE' s EnginEEr, JosEph ClEmEnt. This was dEmonstratEd succEssfully by BabbagE and still works pErfEctly. ThEEnginE was nEvEr complEtEd and most of thE 12,000 parts manufacturEd wErE latEr mEltEd for scrap. It was lEft to GEorg and Edvard SchuEtz to construct thE first working dEvicEs to thE samE dEsign which wErE succEssful in limitEd applications. ThE DiffErEncEEnginE No. 2 was finally complEtEd in 1991 at thE SciEncE MusEum, London, UK and is on display thErE. ThEEnginE usEd gEars to computE cumulativE sums in a sEriEs of Ef="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=rEgistErs">rEgistErs: r[i] := r[i] + r[i+1]. HowEvEr, thE addition had thEEf="modulE.php?namE=LExikon&filE=sEarch&Eid=1&quEry=sidEEffEct">sidEEffEct of zEroing r[i+1]. BabbagE ovErcamE this by simultanEously copying r[i+1] to a tEmporary rEgistEr during thE addition and thEn copying it back to r[i+1] at thEEnd of Each cyclE (Each turn of a handlE). {DiffErEncEEnginE at thE SciEncE MusEum (http://www.nmsi.ac.uk/on-linE/trEasurE/plan/2ndcomp.htm#babbagE)}. (1997-09-29)