India on Thursday launched the largest census exercise — Census 2011—with President Pratibha Patil becoming the first citizen to be enumerated.

Alongside the Census, the preparation of the National Population Register (NPR), aimed to create a comprehensive identity database in the country, will also be prepared.

Later, Vice President Hamid Ansari filled up the formalities for the exercise.

Registrar General and Census Commissioner C Chandramouli and, National Population Register Deputy Director General S K Chakraborty were present on the occasion.

This is the 15th Census since 1872 and 7th since Independence.

India has held Censuses uninterruptedly since 1872, every ten years, through the freedom struggle, partition, wars, floods, earthquakes and Independence, Chandramouli said.

The Census is being conducted in two phases and a total of 25 lakh personnel will be involved in the Rs 2,209 crore exercise.

The total cost covering the NPR preparations, will add upto Rs 5,956 crore.

The first phase, house-listing and housing Census will be conducted between April and July, with each state/UT getting 45 days to complete it. It will begin in Assam, West Bengal, New Delhi, Meghalaya and Goa from Thursday.

Bihar and Jharkhand are the only states that are yet to announce their convenient dates.

The second phase, Population Enumeration will be conducted simultaneously all over the country from February 9 to 28 next year.