Hollerith applied punch card technology, first employed by the Frenchman Joseph-Marie Jacquard in knitting machines, to mechanical tabulating machines. His card, called the Hollerith card, was the same size as a dollar bill. By 1884, Hollerith had developed an electromechanical tabulating machine. It used some of the same technology as an electric telegraph and had the same mechanical counters as an adding machine. We use input devices to perform the two most basic computational tasks, data entry , the process of entering data into computer memory, and issuing commands.
Nothing happens in the CPU until there is data for it to process.
Once data is available, we must give the CPU instructions for what to do with it. In the beginning, before there were keyboards, data had to be manually entered either by flipping switches on the computer or by using something called the punch card. The punch card used to symbolize the computerization of people. The punch card has a pattern of holes punched in it to signify program instructions. To read the cards, electrical contact was made by a pin passing through holes in the card, touching a bath of mercury below.