Density reflects the closeness of data on a disk: the closer the data is, the denser a disk is said to be. Of course, when data is placed closer together (more densely), a disk can store more data. Floppy disks, which are magnetic data storage devices, come in two commonly used sizes: 3.5-inch and 5.25-inch. Both sizes are available in two densities: double- density and high-density.
Inside a floppy disk is a thin piece of film with a magnetic coating. The magnetic coating is where data is stored. Density refers to the amount of magnetic particles in the coating.
Regardless of the size of the particle, it can only store one piece of data. A high-density disk has smaller magnetic particles, which allows more particles to fit on a disk, and makes it possible for the disk to store more data. A double-density disk has larger particles that are not so tightly packed; therefore, it holds less data. (A hard disk, by the way, uses a different type of magnetic material that is much denser than the magnetic material used on any floppy disk. This allows a hard disk to hold a lot more data.)
A 3.5-inch double-density disk can hold 720 kilobytes of data. A 3.5-inch high-density disk can hold 1.44 megabytes of data. A 3.5-inch disk can only be used in a 3.5-inch floppy disk drive. A 5.25-inch double-density disk can hold 360 kilobytes of data, and a 5.25-inch high-density disk can hold 1.2 megabytes. A 5.25-inch disk can only be used in a 5.25-inch floppy drive. It is also important to know what type of density the floppy drive is made to handle. Most new disk drives are high-capacity drives, and can handle both high-density and double-density disks. However, older drives were low-capacity and can only handle double-density disks.