A robot is a mechanical or virtual artificial agent,usually an electro-mechanical machine that is guided by a computer program or electronic circuitry. Robots can be autonomous, semi-autonomous or remotely controlled and range from humanoids such as ASIMO and TOPIO to Nano robots, 'swarm' robots, and industrial robots. By mimicking a lifelike appearance or automating movements, a robot may convey a sense of intelligence or thought of its own. The branch of technology that deals with robots is called robotics.Machinery was initially used for repetitive functions, such as lifting water and grinding grain. With technological advances more complex machines were developed, such as those invented by Hero of Alexandria in the 1st century AD, and the automata of Al-Jazari in the 12th century AD. The robots made by such inventors were more for the purpose of entertainment than for performing work.As mechanical techniques developed through the Industrial age, more practical applications were proposed by Nikola Tesla, who in 1898 designed a radio-controlled boat. Electronics evolved into the driving force of development with the advent of the first electronic autonomous robots created by William Grey Walter in Bristol, England in 1948. The first digital and programmable robot was invented by George Devol in 1954 and was named the Unimate. It was sold to General Motors in 1961 where it was used to lift pieces of hot metal from die casting machines at the Inland Fisher Guide Plant in the West Trenton section of Ewing Township, New Jersey.