Raster scan

A raster scan is like a picture that is made up of tiny dots. Imagine if you took a piece of paper and divided it into lots and lots of little squares, and then colored in each square with a different color to form a picture. That's kind of how a raster scan works.

When we look at a picture on a computer screen, what we're actually seeing is an electronic image created by a beam of light that moves across the screen, one row at a time. This beam of light is called an electron beam, and it shoots out from a special device called a cathode ray tube (or CRT for short).

The electron beam moves across the screen from left to right, and then jumps down to the next row and starts again, moving from left to right once more. It does this very quickly, moving across the screen thousands of times every second, in a pattern that looks kind of like a line that zig-zags back and forth, row by row.

As the electron beam moves across each row, it lights up tiny dots on the screen in different colors to create the picture. Each dot is called a pixel, and the colors are chosen from a large set of possibilities called a color palette.

So when you look at a picture on a computer screen, what you're seeing is really just a lot of little dots that have been lit up in different colors by an electron beam moving back and forth across the screen. This is what we mean when we talk about a raster scan.