The first devices that resemble modern computers date to the mid-20th century (around 1940 - 1945), although the computer concept and various machines similar to computers existed earlier.
Early electronic computers were the size of a large room, consuming as much power as several hundred modern personal computers.
During the authbor's visit to TVA in US in 1962, the grid system was being studied in what is known as system analyser located in a big room. This system had resistors, capcitors etc. behind a panel which required adjustment of values to suit their particular system conditions. This was only time consuming and cumbersome as comapared to modern computers.
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