Data on a floppy disk is encoded via a series of flux transitions. You're familiar with magnets having a north and south pole. We can encode data efficiently on a disk by encoding a '1' bit as a flip in the orientation of the magnetic field.
A lack of a '1' within a given time window encodes a 0. I'm glossing over some details here, but that's basically what you need to know for what I want to show you.