Inside of your mouse that allows it to replicate the movement of your hand to the movement of a little cursor on your screen if you have then you're in the right place because that's what I'll be going over for this video to start with I'll be talking about optical mice which are pretty much the only kind that are still in use today if you hold the mouse slightly above the surface it's on you might notice a little red glow and even if you don't see that you can still see that your mouse has a little hole in it like mine does right here inside that hole there's an optical sensor that is essentially just a tiny little camera with an extremely fast frame rate that is to say it takes a ton of pictures per second there's also a small illuminating light usually an LED that illuminates the surface beneath it which the mouse is placed on this little camera in your mouse constantly takes pictures of the illuminated surface it's on and then compares that picture to the previous one by comparing these two images the computer has all the information it needs to figure out how far your mouse has been pulled along the surface and in what direction the resolution and frame rate of the camera in your mouse determine how accurate smooth and reliable the cursor movement is if the mouse took only 100 pictures per second and you moved your mouse really fast it might have a completely different image than the one it had just before with no overlap and as a result it'll have no way of knowing where the mouse is in relation to where it was beforehand as a result it won't be able to properly replicate that movement onto your screen now likewise if it's resolution were too low let's say only fifty dots per inch it might have trouble comparing the features that define the surface that it's placed on and will get confused you'll see here that the mouse has actually moved further than the camera realizes but because it has such a low resolution it basically has to make assumptions about how specific that movement actually it's for this reason that in most optical mice the camera actually has a frame rate of at least two thousand pictures taken each second though some can have as much as six thousand and they have a resolution of about 1600 pixels per inch and can have as many as four thousand while two thousand images per second might seem mind-blowing keep in mind that neither your mouse nor computer have to store these images once one frame is compared to the previous frame the previous frame is immediately discarded so no data storage is needed it's worth noting that the technology and optical mice was actually pioneered by the military for tracking targets from aircraft the calculations on how much the mouse has moved and in which direction are all done by very simple processing chips in the mouse itself and then it sends that information to your CPU your computer does the rest of the work from here with that data and translates it into the actions you see on your screen these calculations in your CPU occur in what's known as the kernel which is one of the lowest levels of operating systems in your computer this handles all the fundamentally important instructions that keep your computer functioning including being able to receive control inputs such as the mouse this is why sometimes when your programs freeze up for a moment you can still move the mouse just fine that process is given priority over all else because without it you couldn't even interact with the computer to begin with well optical mice are the norm today there was a time when ball mice were the norm now these mice instead of using a small little camera and LED had a rubber ball placed in the middle of them which rolled around as you pulled the mouse across a surface and as this ball rolled it caused these two little adjoining wheels to turn as well which gave your mouse all the data it needed about how it was moving on a two-dimensional x and y plane you may also have seen some of the mice that are controlled by actually rolling a big ball around with your fingers and these mice use the exact same mechanical system but have the advantage of being able to be used in situations where you didn't have access to a large flat surface
