For long library and information technology seems to have meant little more than knowing what tasks had to be performed in libraries and being able to do; only of late did management come to be concerned with such abstractions as planning, controlling, coordinating, etc. Librarians, have sought to justify their professional existence through a set of routine practices which set them apart from other professional groups and which can be accepted by other as necessary for the maintenance of good order in a library. The modern Information technology revolution has led and compelled to recast the entire library and information science system to make it more convenient and easily accessible. Information is an invisible commodity. Like visible commodities, it requires an appropriate distribution mechanism in order to reach end users. This encyclopaedia tries to illustrate complete picture of various aspects related to library and information technology in twenty first century. Encyclopaedia of Library Information Technology for Twenty first Century offers the most thorough treatment available on the application of library science techniques to information management problems.