Floppy disks. Selection of 3.5 inch standard usage computer floppy disks. They are enclosed in variously colored protective jackets. Floppy disks are thin, flexible magnetic disks used to store computer data. The data is arranged on one or both sides at either single or double density. A floppy disk slots into a postbox-type disk drive. Data is read from and written to the disk. Depending on its size and type, a single floppy disk may store 1 megabyte or more of data.