postal index number or pin number is a number which are provided and invented by the postal officers and these numbers may vary in each area, as about the countries each countries may differ from number of numerical which were being used in those nations for example; in India there are total of 6 digit numerical pin code system, and in USA they use 5 digit numerical pin code system, likewise each country uses different numbers of numerical for their pin code. some countries in western side may tend to use the alphanumerical pin code system and these alphanumerical pin code system contains 2 digits of alphabets and 3 or more digits of numerical for their country's pin code.