A well-planned and seamless succession has occurred at Tata Consultancy Services, India's largest IT services firm, with S.Ramadorai, chief executive since 1996, handing over charge Tuesday to Chief Operating Officer N.Chandrasekaran. Chandra, as he's referred to at TCS, took the top job after 22 years at the company, in a career that's included successful stints in the U.S., U.K. and Europe.