ym ic , ▁is ▁applied ▁by ▁ign oring ▁the ▁following ▁space , ▁which ▁may ▁or ▁may ▁not ▁occur . ▁The ▁technical ▁terms ▁the ▁author ▁applies ▁are ▁" letter ▁by ▁letter " ▁or ▁" all ▁through " ▁for ▁the ▁case ▁where ▁spaces ▁are ▁ignored , ▁and ▁" word ▁by ▁word " ▁or ▁" nothing ▁before ▁something " ▁for ▁the ▁case ▁where ▁space ▁comes ▁before ▁A ▁in ▁the ▁alphabet . ▁In ▁actual ▁practice , ▁some ▁indexes , ▁such ▁as ▁the ▁British ▁Union ▁Catalogue ▁of ▁Period ical s , ▁did ▁practice ▁such ▁extensive ▁standard isation . ▁Sometimes ▁by ▁various ▁technical ▁devices ▁such ▁as ▁replacing ▁terms ▁with ▁conventional ▁abbre vi ations ▁that ▁would ▁be ▁the ▁same ▁in ▁all ▁languages . ▁ ▁A ▁US ▁library ▁view ▁( 1 9 4 2 ) ▁for ▁card ▁sorting ▁Donald ▁Kn uth ▁in ▁vol . ▁ 3 ▁of ▁his ▁The ▁Art ▁of ▁Computer ▁Program ming ▁gave ▁a ▁listing ▁showing ▁the ▁operation ▁of ▁around ▁ 4 0 ▁rules , ▁of ▁which ▁" Mc ▁= ▁Mac " ▁was ▁one , ▁for ▁library ▁card ▁sorting . ▁He ▁was ▁cit ing ▁the ▁American ▁Library ▁Association ▁R ules ▁for ▁Fil ing ▁Catalog ▁C ards ▁( 1 9 4 2 ). ▁According ▁to ▁the ▁A LA ▁w iki , ▁it ▁maintain s ▁in ▁print ▁two ▁publications ▁on ▁fil ing ▁rules , ▁one ▁covering ▁that ▁" word - by - word " ▁convention , ▁and ▁another ▁prepared ▁in ▁ 1 9 8 0 ▁that ▁is ▁" letter - by - letter ". ▁A ▁ 1 9 9 8 ▁book