The Postal Department is adding two numbers on right side of the present postal index number that indicates colony or area under that specified post office.

PIN is the abbreviation for Postal Index Number and used on last line of address on envelopes posted and to be dispatched in India. PIN code is introduced in India on 15th August, 1972. The left most number indicates region of an address. There are nine postal regions in India. Each region is a group of few states or union territories. The second number from the left indicates Sub Region, the third number indicates district, fourth number indicates Head Post Office, fifth number and sixth number indicates sub post offices under Head Post office. If the addressee is a famous person under a post office and the envelope is posted in a remote area simply writing his name and PIN CODE on envelope, the envelope will be dispatched.

For example addressee Branch Manager, State Bank of Hyderabd, PIN CODE: 509 301. "5" first letter from left indicates states of Andhra Pradesh, Karnataka and Yanam (UT). "0" second letter indicates Telangana region in Andhra Pradesh and "9" indicates Mahbubnagar District. "301" indicates Jadcherla Head Post Office in Mahbubnagar District. So the envelope can be dispatched to Branch Manager, State Bank of Hyderabad, Jadcherla who is well known to the post master Jadcherla.

POSTAL REGIONS IN INDIA:

Region No:	States/UTs
1	Delhi, Haryana, Punjab, Himachala Pradesh, Jammu & Kashmir and Chandigarh
2	Uttar Pradesh and Uttar Khand
3	Rajasthan, Gujarath, Daman & Dayyu, Dadra & Nagar Haveli
4	Chattish Ghad, Maharastra, Madhya Pradesh and Goa
5	Andhra Pradesh, Karnataka and Yanam (Pandichery)
6	Kerala, Tamilnadu, Puduchery (Pandichery) Laksha Dweep
7	West Bengal, Orrissa, Assam, Sikkim, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura, Meghalaya, Andaman Nicobar Islands
8	Bihar and Jarkhand
9	Army Post Office, Field Post Office

The first time PIN code is used in the world in 1941 in Germany, next in 1959 in Britain and in 1963 in America (ZIP CODE). Universal Postal Union is organized with 190 countries in the world. The system is not followed by few countries like Ireland, Hang Kong, Panama, and Vietnam.