Necessity is the mother of invention. The saying holds true for computers too. Researches invented computers because of man's search for fast accurate calculating devices. Blaise pascal invented the first mechanical adding machine in 1642. Later, in the year 1671, Baron Gottfried Wilhelm von Leibniz of Germany invented the first calculator for multiplication. Keyboard machines originated in the United States around 1880 and we use them even today. Around the same period, Herman Hollerith came up with the concept of punched cards that computers used extensively as input medium evens in late 1970s. Business machines and calculators made their appearance in Europe and America towards the end of the nineteenth century.
Charlies Babbage, a nineteenth century professor at Cambridge University, is considered the father of modern digital programmable computers. He had employed a group of clerks for preparing mathematical and statistical tables. Babbage had to spend several hours checking these tables because even utmost care and precautions could not eliminate human errors Soon he became dissatisfied and exasperated with this type of monotonous job. As a result, he started thinking about building a machine that could compute tables guaranteed to be error-free. In 1842, Babbage came out with this new of a completely automatic Analytical Engine for performing basic arithmetic functions for any mathematical problem at idea an average speed of 60 additions per minute.
Unfortunately, he was unable to produce a working model of this machine because the precision engineering required to manufacture the machine was not available during that period. However, his efforts precision established a number of principles that are fundamental to the design of any digital programmable computer. A major drawback of the early automatic calculating machines was that their programs were wired on boards that made it difficult to change programs. In 1940s, Dr. John Von neumann introduced the "stored program" concept that helped in overcoming hard-wired program problem. The basic idea behind this concept is that a sequence of instructions and data can be stored in memory of a computer automatically directing flow of operations.
This feature considerably influenced development of modern digital computers because of ease with which different programs can be loaded and executed on a single computer. Due to this features, we often refer to modern digital computers as stored program digital computers.