A Postal Index Number or PIN or Pincode is a code in the post office numbering or post code system used by India Post, the Indian postal administration.
The code is six digits long.
The PIN Code system was introduced on 15 August 1972 by Mr.Shriram Bhikaji Velankar.
The system was introduced to simplify the manual sorting and delivery of mail by eliminating confusion over incorrect addresses, similar place names and different languages used by the public
The first three digits of the PIN represent a specific geographical region called a sorting district that is headquartered at the main post office of the largest city and is known as the sorting office.
A state may have one or more sorting districts depending on the volumes of mail handled.
There are nine PIN zones in India, including eight regional zones and one functional zone (for the Indian Army).
The first digit of the PIN code indicates the region.
The second digit indicates the sub-region .
The third digit indicates the sorting district within the region.
The fourth digit represents the route on which a Delivery office is located in the sorting district . This is 0 for offices in the core area of the sorting district.
The last two digits represent the delivery office within the sorting district starting from 01 which would be the GPO or HO.
The numbering of the delivery office is done chronologically with higher numbers assigned to newer delivery offices.
If the volume of mails handled at a delivery office is too large, a new delivery office is created and the next available PIN is assigned .
Thus two delivery offices situated next to each other will only have the first four digits in common.