Hindustan Aircraft was founded in Bengaluru in 1940 by Walchand Hirachand and later became Hindustan Aeronautics Limited (HAL). After independence the central government set up several large public-sector companies here, including Indian Telephone Industries, Bharat Electronics, Hindustan Machine Tools (famous for HMT watches) and BEML.
The Indian Space Research Organisation has its headquarters in the city. The engineers, scientists and technicians these institutions trained became the workforce that made the IT boom possible.
Further reading: Hindustan Aeronautics Limited on Wikipedia.