Man has always been in search of mechanical aids for computation. The development of the abacus around 3000 BC introduced the positional notation of number systems. In seventeenth-century France, Pascal and Leibnitz developed mechanical calculators that were later developed into desk calculators. In 1801, Jacquard used punched cards to instruct his looms in weaving various patterns on cloth. In 1822, Charles Babbage, an Englishman, developed the difference engine, a mechanical device that carried out a sequence of computations specified by the settings of levers, gears, and cams. Data were entered manually as the computations progressed. Around 1820, Babbage proposed the analytical engine, which would use a set of punched cards for program input, another set of cards for data input, and a third set of cards for output of results. The mechanical technology was not sufficiently advanced and the analytical engine was never built; nevertheless, the analytical engine as designed probably was the first computer in the modern sense of the word. Several unit-record machines to process data on punched cards were developed in the United States in 1880 by Herman Hollerith for census applications. In 1944, Mark I, the first automated computer, was announced. It was an electromechanical device that used punched cards for input and output of data and paper tape for program storage. The desire for faster computations than those Mark I could provide resulted in the development of ENIAC, the first electronic computer built out of vacuum tubes and relays by a team led by Americans Eckert and Mauchly. ENIAC employed the stored-program concept in which a sequence of instructions (i.e., the program) is stored in the memory for use by the machine in processing data. ENIAC had a control board on which the programs were wired. A rewiring of the control board was necessary for each computation sequence. John von Neumann, a member of the Eckert–Mauchly team, developed EDVAC, the first stored-program computer. At the same time, Wilkes developed EDSAC, the first operational stored-program machine, which also introduced the concept of primary and secondary memory hierarchy. Von Neumann is credited for developing the stored-program concept, beginning with his 1945 first draft of EDVAC. The structure of EDVAC established the organization of the storedprogram computer (von Neumann machine), which contains
1. An input device through which data and instructions can be entered
2. A storage unit into which results can be entered and from which instructions and
data can be fetched
3. An arithmetic unit to process data
4. A control unit to fetch, interpret, and execute the instructions from the storage
5. An output device to deliver the results to the user
