The 19th Century: First Programmable Computing Devices Until the 19th century "early computers", probably better described as calculating machines, were basically mechanical devices and operated by hand. Early calculators like the abacus worked with a system of sliding beads arranged on a rack and the centerpiece of Leibniz's multiplier was a stepped-drum gear design. Therefore Charles Babbage's proposal of the Difference Engine (1822), which would have (it was never completed) a stored program and should perform calculations and print the results automatically, was a major breakthrough, as it for the first time suggested the automation of computers. The construction of the Difference Engine, which should perform differential equations, was inspired by Babbage's idea to apply the ability of machines to the needs of mathematics. Machines, he noted, were best at performing tasks repeatedly without mistakes, while mathematics often required the simple repetition of steps. After working on the Difference Engine for ten years Babbage was inspired to build another machine, which he called Analytical Engine. Its invention was a major step towards the design of modern computers, as it was conceived the first general-purpose computer. Instrumental to the machine's design was his assistant, Augusta Ada King, Countess of Lovelace, the first female computer programmer. The second major breakthrough in the design of computing machines in the 19th century may be attributed to the American inventor Herman Hollerith. He was concerned with finding a faster way to compute the U.S. census, which in 1880 had taken nearly seven years. Therefore Hollerith invented a method, which used cards to store data information which he fed into a machine that compiled the results automatically. The punch cards not only served as a storage method and helped reduce computational errors, but furthermore significantly increased speed. Of extraordinary importance for the evolution of digital computers and artificial intelligence have furthermore been the contributions of the English mathematician and logician George Boole. In his postulates concerning the Laws of Thought (1854) he started to theorize about the true/false nature of binary numbers. His principles make up what today is known as Boolean algebra, the collection of logic concerning AND, OR, NOT operands, on which computer switching theory and procedures are grounded. Boole also assumed that the human mind works according to these laws, it performs logical operations that could be reasoned. Ninety years later Boole's principles were applied to circuits, the blueprint for electronic computers, by Claude Shannon.

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Satellites Communications satellites are relay stations for radio signals and provide reliable and distance-independent high-speed connections even at remote locations without high-bandwidth infrastructure. On point-to-point transmission, the transmission method originally employed on, satellites face increasing competition from fiber optic cables, so point-to-multipoint transmission increasingly becomes the ruling satellite technology. Point-to-multipoint transmission enables the quick implementation of private networks consisting of very small aperture terminals (VSAT). Such networks are independent and make mobile access possible. In the future, satellites will become stronger, cheaper and their orbits will be lower; their services might become as common as satellite TV is today. For more information about satellites, see How Satellites Work (http://octopus.gma.org/surfing/satellites) and the Tech Museum's satellite site (http://www.thetech.org/hyper/satellite). http://www.whatis.com/vsat.htm http://octopus.gma.org/surfing/satellites

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