The history of the development of the computer, starting with Charles Babbage's mechanical Difference Engine in the 1820s and Herman Hollerith's punch-card tabulating machines of the 1890s, through the development of the first vacuum-tube machines in World War II (Colossus and ENIAC) followed by continuing miniaturization enabled by the transistor, integrated circuit, and microprocessor, to the beginnings of the personal computer revolution led by Steve Wozniak, Steve Jobs, and Bill Gates.