Come April 1, India will kickstart the largest census exercise ever to be attempted in the history of mankind and capture its 1.2 billion population in one single database.

More than 2.5 million people will be engaged in the Rs 2,200 crore 2011 National Census project in which President Pratibha Patil will be the first person to be enumerated on Thursday.

Government made it clear that no information will be collected on castes as no caste-based census has ever been conducted in Independent India.

To create a comprehensive identity database in the country, the government will attempt to identify every member of its 1.2 billion population in 35 states and Union Territories in the census in perhaps its most ambitious national project.

During the mammoth exercise, the enumerators for the first time will collect information like ownnership of mobile phones, computers, internet, having treated or untreated drinking water facility and obtain finger prints and photographs which will help government formulate plans and strengthen the country's security.

Home Secretary Gopal K Pillai said after completion of the exercise, the largest census to be attempted in the history of mankind, a National Population Register (NPR) will be created in which the government will have the entire population of the country under one database.

"Once the NPR is completed we will have the photographs of the entire population. First time we will be able to have specific information about the entire usual residents of the country," he told a press conference here.

Pillai said once the NPR was completed, the government will give a unique number to each resident.

The Census operation would cost around Rs 2209 crore while the approved cost of the scheme for creation of NPR is Rs 3539.24 crore.

This is for the first time that NPR is being prepared. The database will be built, maintained and updated by the Registrar General and Census Commissioner of India.

Census 2011 will be conducted in two phases. The first phase, called the Houselisting and Housing Census, will be conducted between April and July, depending on the convenience of different States/UTs.

This operation is to be conducted over a period of 45 days in each State/UT. Thus a State starting on the April 1 will finish on the May 15 and so on. The details required for creating the NPR will also be canvassed during this phase.

The second phase, called the Population Enumeration phase, will be conducted simultaneously all over the country from February 9 to 28, 2011.

The Census would cover all 640 districts, 5,767 tehsils, 7,742 towns and more than 6 lakhs villages. More than 24 crores households will be visited and 1.20 billion people enumerated during this exercise.