Random Scan Display

In Random Scan Display, the electron beam is directed straightway to the particular points of the screen where the image is to be produced. Random Scan Display generates the image by drawing a set of random straight lines much in the same way one might move a pencil over a piece of paper to draw an image – drawing strokes from one point to another, one line at a time. this is why this technique is also referred to as Vector Scan Display.

Random-Scan Display

No bit planes are containing mapped pixel values in the vector systems. Instead of the Display Buffer memory stores a set of line-drawing commands along with endpoint coordinates in a display list or display program created by a graphics package. The display processing unit (DPU) executes each command during every refresh cycle and feeds the vector generator with digital x, y, Δx, Δy values.
The vector generator converts the digital signals into an equivalent analog deflection voltage. This causes the electron beam to move to the start point or from the start point to the endpoint of a line or vector. Thus the beam sweep does not follow any fixed pattern. The direction is arbitrary as dictated by the display commands. When the beam focus must be moved from the end of one stroke to the beginning of the other, the beam intensity is set to 0.

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    5. Output Devices
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