5.1" floppy. These are the original floppy disks, and they really were floppy. Because of their soft covers they were easily bent or creased. But people loved them because it made it easy to carry 360kb of data around.Floppy disk
This is a floppy disk. These are one of the oldest ways of storing data on a computer. They are not always reliable, and many modern computers do not even have anywhere to put a floppy disk into.
5.1" floppy. These are the original floppy disks, and they really were floppy. Because of their soft covers they were easily bent or creased. But people loved them because it made it easy to carry 360kb of data around.
3.5" floppy. The size was chosen so that it fitted exactly into a man's shirt pocket. With its hard case and 1.44mb of memory this is one of the most successful kinds of storage ever made. There are literally millions of 3.5" floppy disks in use around the world.