ഇന്ത്യയിലെ തപാൽ സംവിധാനം ( Postal System in India ) : Postal Index Number (PIN) / PIN Code

    Postal Index Number (PIN) / PIN Code is a 6 digit code of Post Office numbering used by India Post. The PIN Code system in India was introduced on 15 August 1972 by 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.

    There are 9 PIN regions in the country. The first 8 are geographical regions and the digit 9 is reserved for the Army Postal Service. The first digit indicates one of the regions. The first 2 digits together indicate the sub region or one of the postal circles. The first 3 digits together indicate a sorting district. The last 3 digits refer to the delivery Post Office. 

PIN zones cover the Indian states and union territories:

• 1 - Delhi, Haryana, Punjab, Himachal Pradesh, Jammu and Kashmir, Chandigarh
• 2 - Uttar Pradesh, Uttarakhand
• 3 - Rajasthan, Gujarat, Daman and Diu, Dadra and Nagar Haveli
• 4 - Goa, Maharashtra, Madhya Pradesh, Chhattisgarh
• 5 - Telangana, Andhra Pradesh, Karnataka
• 6 - Tamil Nadu, Kerala, Puducherry, Lakshadweep
• 7 - Odisha, West Bengal, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura, Meghalaya, Andaman and Nicobar Islands, Assam, Sikkim
• 8 - Bihar, Jharkhand
• 9 - Army Post office (APO) and Field Post office (FPO)

Reference : http://www.indiapost.gov.in/