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How do the pictures on computer screens get there?

Are you asking how the screens work? Most screens are "CRT", which means "cathode-ray-tube", which is the same principle that a TV uses (though usually with a different, higher, resolution). There is an electron "gun" that turns rapidly on and off, scanning the screen and exciting the "phosphors" on the surface that actually give out the light. There are also liquid crystal and plasma displays, both of which have many elements that are controlled simultaneously, rather than a single scanning element. Other than that, pictures get to computer screens because people told the computers what to put there. Usually there is a special area of computer memory (sometimes on a special graphics card) that contains a map of the screen, with, say, a 1 for a point on the screen that should be on, and a 0 for a point that should be off. The hardware then converts this into the appropriate signals for the type of display you have. The 1's and 0's get into the video "frame buffer" through the graphics operations available on your computer. There are lots of books on computer graphics with much more information on all this!

Arthur Smith

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