▁type ▁of ▁C RT ▁computer ▁display ▁which ▁was ▁very ▁common ▁in ▁the ▁early ▁days ▁of ▁computing , ▁from ▁the ▁ 1 9 6 0 s ▁through ▁the ▁ 1 9 8 0 s , ▁before ▁color ▁mon itors ▁became ▁popular . ▁The ▁most ▁important ▁component ▁in ▁the ▁monitor ▁is ▁the ▁picture ▁t ube . ▁C RT ▁basically ▁means ▁c ath ode ▁ray ▁t ube . ▁The ▁C RT ▁use ▁c ath ode - ray - t ube ▁technology ▁to ▁display ▁images , ▁so ▁they ▁are ▁large , ▁bul ky ▁and ▁heavy ▁like ▁conventional ▁or ▁old ▁televis ions , ▁because ▁old ▁televis ions ▁also ▁used ▁the ▁C RT ▁technology ▁only ▁to ▁display ▁the ▁television ▁films ▁or ▁television ▁images . ▁To ▁form ▁the ▁image ▁on ▁the ▁screen , ▁an ▁electronic ▁gun ▁se aled ▁inside ▁a ▁large ▁glass ▁t ube ▁fires ▁electrons ▁at ▁ph osph orous ▁co ated ▁screen ▁to ▁light ▁up ▁the ▁appropriate ▁pixels ▁in ▁the ▁appropriate ▁color ▁to ▁display ▁images . ▁The ▁ph osph ors ▁g low ▁only ▁for ▁a ▁limited ▁period ▁of ▁time ▁after ▁the ▁expos ure ▁of ▁the ▁electrons , ▁the ▁monitor ▁image ▁must ▁be ▁red ra wn / refresh ed ▁on ▁a ▁contin ual ▁basis . ▁Typ ical ▁refresh ment ▁rates ▁are ▁between ▁ 6 0 ▁and ▁ 8 5 ▁times ▁in ▁a ▁second . ▁ ▁They ▁are ▁still ▁widely ▁used ▁in ▁applications ▁such ▁as ▁computer ized ▁c ash ▁register ▁systems . ▁Green ▁screen ▁was ▁the ▁common ▁name ▁for ▁a ▁mon och rome ▁monitor ▁using ▁a ▁green ▁" P 1 "