A postal index number or PIN or PIN code is a code in the postal numbering system or postal code used by India Post, the postal administration of India. The code has six digits.The PIN code system was introduced on August 15, in the year 1972 by Shriram Bhikaji Velankar,an additional secretary in the Union Communications Ministry. The system was introduced to simplify manual sorting and mail delivery by eliminating confusion about incorrect addresses, similar place names and various languages used by the public.There are nine PIN zones in India, including eight regional zones and one functional zone.The first digit of PIN code indicates the region. The second digit will indicates the subregion and the third digit will indicates the classification district within the region.
The final three digits are assigned to individual post offices.The first three digits of the PIN represent a specific geographic region called a classification district that is headquartered in the main post office of the largest city and is known as the classification office. A state may have one or more classification districts depending on the volumes of mail handled.The fourth digit represents the route in which a delivery office is located in the classification district. This is 0 for offices in the central area of the classification district.The last two digits represent the delivery office within the classification district from 01, which would be the GPO or HO.
The numbering of the delivery office is made chronologically with higher numbers assigned to new delivery offices. If the volume of mails handled in a delivery office is too large, a new delivery office is created and the next available PIN is assigned. Thus, two delivery offices located next to each other will only have the first four digits in common.Each PIN code is assigned exactly to a delivery post office that receives all mail that will be delivered to one or more lower offices within its jurisdiction, all of which share the same code. The delivery office can be a general post office (GPO), a main office (HO) or a secondary office (SO) that are usually located in urban areas. The post of the delivery office is classified and routed to other delivery offices for a different PIN or for one of the sub offices or branches relevant to the same PIN. The branches (BO) are located in rural areas and have limited postal services.