Late 1970s - Present: Fourth Generation Computers Following the invention of the first integrated circuits always more and more components could be fitted onto one chip. LSI (Large Scale Integration) was followed by VLSI (Very Large Scale Integration) and ULSI (Ultra-Large Scale Integration), which increased the number of components squeezed onto one chip into the millions and helped diminish the size as well as the price of computers. The new chips took the idea of the integrated circuit one step further as they allowed to manufacture one microprocessor which could then be programmed to meet any number of demands. Also, ensuing the introduction of the minicomputer in the mid 1970s by the early 1980s a market for personal computers (PC) was established. As computers had become easier to use and cheaper they were no longer mainly utilized in offices and manufacturing, but also by the average consumer. Therefore the number of personal computers in use more than doubled from 2 million in 1981 to 5.5 million in 1982. Ten years later, 65 million PCs were being used. Further developments included the creation of mobile computers (laptops and palmtops) and especially networking technology. While mainframes shared time with many terminals for many applications, networking allowed individual computers to form electronic co-operations. LANs (Local Area Network) permitted computers to share memory space, information, software and communicate with each other. Although already LANs could reach enormous proportions with the invention of the Internet an information and communication-network on a global basis was established for the first time.

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Bandwidth The bandwidth of a transmitted communications signal is a measure of the range of frequencies the signal occupies. The term is also used in reference to the frequency-response characteristics of a communications receiving system. All transmitted signals, whether analog or digital, have a certain bandwidth. The same is true of receiving systems. Generally speaking, bandwidth is directly proportional to the amount of data transmitted or received per unit time. In a qualitative sense, bandwidth is proportional to the complexity of the data for a given level of system performance. For example, it takes more bandwidth to download a photograph in one second than it takes to download a page of text in one second. Large sound files, computer programs, and animated videos require still more bandwidth for acceptable system performance. Virtual reality (VR) and full-length three-dimensional audio/visual presentations require the most bandwidth of all. In digital systems, bandwidth is data speed in bits per second (bps). Source: Whatis.com

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