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Difference between Raster Scan System and Random Scan System

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Base of Difference

Raster Scan System

Random Scan System

Electron Beam

The electron beam is swept across the screen, one row at a time, from top to bottom.

The electron beam is directed only to the parts of screen where a picture is to be drawn.


Its resolution is poor because raster system in contrast produces zig-zag lines that are plotted as discrete point sets.

Its resolution is good because this system produces smooth lines drawings because CRT beam directly follows the line path.

Picture Definition

Picture definition is stored as a set of intensity values for all screen points, called pixels in a refresh buffer area.

Picture definition is stored as a set of line drawing instructions in a display file.

Realistic Display

The capability of this system to store  intensity values for  pixel makes it well suited for the realistic display of scenes contain shadow and color pattern.

These systems are designed for line-drawing and can’t display realistic shaded scenes.

Draw an Image

Screen points/pixels are used to draw an image.

Mathematical functions are used to draw an image.




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