Anabacusisaformofmanuallyoperatedcountingaid.IthasoriginatedinChinaover2,600yearsago.ItisoneofthemostimportantinventionsofancientChina.TheabacususedtobethemostwidelyusedcalculationtoolbeforetheappearanceofArabicnumerals.Atpresent,abacusescontinuetobeusedinpartsofAsiaandtheMiddleEast,especiallyintheshops,andtheyareavailableinstoreswhichstockChineseorJapanesegoods.IntheWest,itissometimesusedtohelpyoungchildrengraspnumbers,andsomemathematiciansenjoyexperimentingwiththeabacustoworkoutsimplearithmeticalproblems.