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.