<P> For 40 years, the arithmometer was the only mechanical calculator available for sale and was sold all over the world . By then, in 1890, about 2,500 arithmometers had been sold plus a few hundreds more from two licensed arithmometer clone makers (Burkhardt, Germany, 1878 and Layton, UK, 1883). Felt and Tarrant, the only other competitor in true commercial production, had sold 100 comptometers in three years . </P> <P> The 19th century also saw the designs of Charles Babbage calculating machines, first with his difference engine, started in 1822, which was the first automatic calculator since it continuously used the results of the previous operation for the next one, and second with his analytical engine, which was the first programmable calculator, using Jacquard's cards to read program and data, that he started in 1834, and which gave the blueprint of the mainframe computers built in the middle of the 20th century . </P> <Ul> <Li> In 1851, Thomas de Colmar simplified his arithmometer by removing the one digit multiplier / divider . This made it a simple adding machine, but thanks to its moving carriage used as an indexed accumulator, it still allowed for easy multiplication and division under operator control . The arithmometer was now adapted to the manufacturing capabilities of the time; Thomas could therefore manufacture consistently a sturdy and reliable machine . Manuals were printed and each machine was given a serial number . Its commercialization launched the mechanical calculator industry . Banks, insurance companies, government offices started to use the arithmometer in their day - to - day operations, slowly bringing mechanical desktop calculators into the office . </Li> <Li> In 1878 Burkhardt, of Germany, was the first to manufacture a clone of Thomas' arithmometer . Until then Thomas de Colmar had been the only manufacturer of desktop mechanical calculators in the world and he had manufactured about 1,500 machines . Eventually twenty European companies will manufacture clones of thomas' arithmometer until WWII . </Li> <Li> Dorr E. Felt, in the U.S., patented the Comptometer in 1886 . It was the first successful key - driven adding and calculating machine . ("Key - driven" refers to the fact that just pressing the keys causes the result to be calculated, no separate lever or crank has to be operated . Other machines are sometimes called "key - set".) In 1887, he joined with Robert Tarrant to form the Felt & Tarrant Manufacturing Company . The comptometer - type calculator was the first machine to receive an all - electronic calculator engine in 1961 (the ANITA mark VII released by Sumlock comptometer of the UK). </Li> <Li> In 1890 W.T. Odhner got the rights to manufacture his calculator back from Königsberger & C, which had held them since it was first patented in 1878, but had not really produced anything . Odhner used his Saint Petersburg workshop to manufacture his calculator and he built and sold 500 machines in 1890 . This manufacturing operation shut down definitively in 1918 with 23,000 machines produced . The Odhner Arithmometer was a redesigned version of the Arithmometer of Thomas de Colmar with a pinwheel engine, which made it cheaper to manufacture and gave it a smaller footprint while keeping the advantage of having the same user interface . </Li> <Li> In 1892 Odhner sold the Berlin branch of his factory, which he had opened a year earlier, to Grimme, Natalis & Co...They moved the factory to Braunschweig and sold their machines under the brand name of Brunsviga (Brunsviga is the Latin name of the town of Braunschweig). This was the first of many companies which would sell and manufacture clones of Odhner's machine all over the world; eventually millions were sold well into the 1970s . </Li> <Li> In 1892, William S. Burroughs began commercial manufacture of his printing adding calculator Burroughs Corporation became one of the leading companies in the accounting machine and computer businesses . </Li> <Li> The "Millionaire" calculator was introduced in 1893 . It allowed direct multiplication by any digit - "one turn of the crank for each figure in the multiplier". It contained a mechanical product lookup table, providing units and tens digits by differing lengths of posts . (1) Another direct multiplier was part of the Moon - Hopkins billing machine; that company was acquired by Burroughs in the early 20th century . </Li> </Ul> <Li> In 1851, Thomas de Colmar simplified his arithmometer by removing the one digit multiplier / divider . This made it a simple adding machine, but thanks to its moving carriage used as an indexed accumulator, it still allowed for easy multiplication and division under operator control . The arithmometer was now adapted to the manufacturing capabilities of the time; Thomas could therefore manufacture consistently a sturdy and reliable machine . Manuals were printed and each machine was given a serial number . Its commercialization launched the mechanical calculator industry . Banks, insurance companies, government offices started to use the arithmometer in their day - to - day operations, slowly bringing mechanical desktop calculators into the office . </Li>

Write any three difference between computer and calculator