A double-sided disk is a floppy disk on which data can be recorded on both sides. The storage capacity of a double-sided disk is twice that of a disk on which data can be stored on just one side. Double-density, double-sided disks have an average storage capacity of 720,000 bytes, equivalent to approximately 360 printed pages of information. A high-density double-sided disk, on which the tracks used to store information are spaced closer together, can store up to 1,440,000 bytes.

A double-sided disk drive is necessary for data storage on both sides of a disk. A disk drive reads data from and writes data to a disk. This does not often pose a problem, however, since most modern computer systems come equipped with a double-sided disk drive.

A floppy disk is constructed of plastic. With double-sided disks, the plastic is coated on both sides with a material known as magnetic oxide. Data is stored on circular tracks within the magnetic oxide matrix. Each track is divided into arcs called sectors. Formally a physical process, sectors are now made by writing codes on the disk during a process of disk preparation called formatting, or initialization. Following formatting, the computer uses the disk side number, a track number and a sector number to form an address for the data written to each site. The addresses facilitate the subsequent use or retrieval of the data.