▁other ▁than ▁identification ". ▁ ▁For ▁the ▁purposes ▁of ▁naming , ▁the ▁term ▁" number " ▁is ▁often ▁used ▁lo os ely ▁to ▁refer ▁to ▁any ▁ ▁string ▁( sequence ▁of ▁symbols ), ▁which ▁may ▁not ▁consist ▁entirely ▁of ▁digits — it ▁is ▁often ▁al phan umeric . ▁For ▁instance , ▁UK ▁National ▁In sur ance ▁numbers , ▁some ▁driver ' s ▁license ▁numbers , ▁and ▁some ▁serial ▁numbers ▁contain ▁letters . ▁ ▁Use ▁of ▁nom inal ▁numbers ▁" N om inal " ▁refers ▁to ▁the ▁use ▁of ▁numbers : ▁any ▁nom inal ▁number ▁can ▁be ▁used ▁by ▁its ▁numerical ▁value ▁as ▁an ▁integer — added ▁to ▁another , ▁multip lied , ▁compared ▁in ▁magnitude , ▁and ▁so ▁forth — but ▁for ▁nom inal ▁numbers ▁these ▁operations ▁are ▁not , ▁in ▁general , ▁meaning ful . ▁For ▁example , ▁the ▁Z IP ▁code ▁ 1 1 1 1 1 ▁is ▁less ▁than ▁the ▁Z IP ▁code ▁ 1 2 3 4 5 , ▁but ▁that ▁does ▁not ▁mean ▁that ▁ 1 1 1 1 1 ▁was ▁issued ▁before ▁ 1 2 3 4 5 ▁or ▁that ▁the ▁region ▁denoted ▁by ▁ 1 1 1 1 1 ▁is ▁further ▁south ▁than ▁ 1 2 3 4 5 , ▁though ▁it ▁might ▁be . ▁Similarly , ▁one ▁can ▁add ▁or ▁subtract ▁Z IP ▁codes , ▁but ▁this ▁is ▁meaning less : ▁ ▁does ▁not ▁have ▁any ▁meaning ▁as ▁a ▁Z IP ▁code . ▁ ▁In ▁general , ▁the ▁only ▁meaning ful ▁operation ▁with ▁nom inal