Floppy Disks

Floppy disks are removable, direct access storage media inserted into disk drives. Floppy disks are flat, circular pieces of Mylar plastic that rotate within a jacket. These are also called flexible disks, floppies, Diskettes or simply disks.
Data and instructions are stored as forms of bits and bytes using the ASCII or EBCDIC data coding schemes. They are stored as electromagnetic charges on a disk surface. The two most common disks are 5 1/4-inch (5.25") and 3 1/2-inch (3.5") in their diameter. More efficient size, high storage capacity and sturdier design of a 3.5"-disk make microcomputers now use the 3.5" disks more.

Tracks/Sectors

• Track: The disk surface is divided into several concentric circles called tracks. The thinner the tracks, the more storage capacity of the disk. Data are recorded as tiny spots on these tracks. These tracks are closed concentric circles, not a single spiral. Each track has the same number of bits although the outer tracks are longer than the inner ones.

• Sector: The circular tracks are further divided into wedge-shaped sections known as sectors. The fields of data within a particular record are organized according to tracks and sectors on a disk. - graph

Hard / Soft Sectored Disks and Formatting

There are two kinds of sectors for a disk. A hard sectored disk is one and a soft sectored disk is the other. The hard sectored disk identifies sectors with some physical marks on the disk, whereas the soft sectored disk identifies sectors with sector identification contained in the recording tracks.
A format program places the sector identification on the disk. When a user buys a disk manufactured without tracks and sectors in place (this kind of disk does not have "Formatted" label on it), he or she must put the tracks and sectors using a format program.

Capacity

• DS/DD (2S/2D) Disk: DS/DD means Double Sided Double Density. This is a floppy disk recorded on both of its sides (DS) and has twice the capacity of the prior format (DD). For the IBM and IBM compatible PCs, DD/DS disk usually has 40 tracks on each side and each side contains 9 sectors of 512 bytes each.
  DS/DD: 360KB
  DS/DD: 720 KB (PCs), 800 KB for Mac formats.

• DS/HD Disk: DS/HD means Double Sided High Density. An HD disk has increased storage capacity usually with more tracks per square inch. For IBM and IBM compatible PCs, an HD disk is usually formatted to have 80 tracks on each side. Each side then contains 18 sectors of 512 bytes each - double capacity of a DD disk.
  DS/HD: 1.2MB
  DS/HD: 1.44 MB (PCs), 1.44 MB for Mac formats.

Floppy Drives

A floppy drive grabs a disk at its center and spins it inside its plastic jacket. The floppy drive obtains stored data and instructions from a floppy disk and stores them onto the disk. The drive is made up of a box with a slot into which a user inserts a disk. The slot has a drive gate. This drive rotates the disk with a motor inside the drive. Electronic read/write heads "read" data from the disk and "write" data to it while the disk rotates.
A microcomputer usually has internal floppy drives inside the computer cabinet, but it sometimes has external floppy drive, a separate component outside the cabinet.

Working Process of Floppy Drive

• Inserting disk: Inserting a disk to let it work.
  
• Closing gate: After inserting, the drive gate should be closed. This places the disk around a spindle and holds it.
  
• Revolving: Spinning the disk inside the jacket.
  
• Reading/ Writing: Read- write heads on an access arm transfer data signals from disk to computer or computer to disk.
  
• Seek: Seek operation is to let the access arm move the read-write head to the requested track on the disk.
  
• Search: Search operation is to let the drive rotate the disk to the proper position.

Read-Write Head: A device that reads and writes data on a magnetic disk. For writing, the surface of the disk is moved past the read/write head. Bits of data are recorded as tiny, magnetized spots of positive or negative polarity, by discharging electrical impulses at the appropriate times. For reading, the bits on a disk induce an electrical current across the read head.

Access arm: This is a mechanical arm that moves the read/write head across the surface of a disk. The access arm is directed by the operating system to move the read/write head to a specific track on the disk.