Leibnitz conceptualized the concept of a computer in the 17th century. In the 19th century, Babage made advances in mechanical computers. By World War II, warships had mechanical computers in the form of fire control systems. The British (Turing) built the first digital computer and used it to break the German code in World War II. After World War II, the Americans built a digital computer using vacuum tubes for military ballistic studies. The builder of this computer, Univac (now part of Unisys), projected the demand for computers at 4, but IBM projected a much larger market.
Advances in computers are made possible by advances in microelectronics. This is because (1) mechanical computers are far too large and too inaccurate, and (2) vacuum tube computers consume a great deal of power and break down frequently. What made the computer a commercial success was the invention of an inexpensive, reliable transistor, which required very little power. At first, transistors in computers were individually wired components. Technological advance lead to boards with individual components, and finally to boards with integrated circuits. The advance in microelectronics has made the digital computer dominant over other types of computers because of its lower cost and higher performance.