The vital part of Census 2011 -- the population enumeration -- will be conducted across the country simultaneously between February 9 and 28.

Registrar-General and Census Commissioner C Chandramouli today said the biggest-ever census attempted in the history of mankind enumerating the country's 1.2 billion population will be conducted across 35 states and Union Territories.

During the massive exercise, all citizens of the country will be counted classifying various factors and according to their gender, religion, occupation and education.

Enumerators for the first time will collect information like ownership of mobile phones, computers, internet, having treated or untreated drinking water facility and usage of banking services. They will also seek additional information for the creation of National Population Register (NPR).

However, information about caste will not be collected in this phase but through a separate phase to be conducted between June and September 2011.

The Rs 2,200 crore exercise will cover all citizens living in 7,742 towns and six lakh villages in 640 districts of India. With the expenditure of just Rs 18.33 for each person, this census is also being considered as the most cost-effective.

"To carry out this massive exercise more than 2.5 million people will be engaged. The fact that many countries in the world do not have a population equal to the number of officials that conduct the Indian census is an indication of the size of this operation," Chandramouli said at a function organised for unveiling the logo of enumerators.

The logo was unveiled by Home Minister P Chidambaram.

The massive exercise, to be spread over next 11 months, will mark a milestone as the first-ever NPR will also be prepared in which all persons aged over 15 years will be photographed and fingerprinted to create a biometric national database.

With this, India will probably become the first democratic nation in the world which would have got its population fingerprinted in a year from now.

Once the NPR final database is created, the same will be sent to Unique Identification Authority of India for duplication and generation of UID number and for issuing proposed identity smart card.

The population enumeration has already been done in snow-bound areas in Himachal Pradesh, Jammu and Kashmir and some other parts of the country.

The data of migrant population will be collected on the night of February 28 at airports, railway stations, sea ports and bus terminals.