Floppy Drive Storage
The original purpose of floppy drives was to store data and transport data in a useable form. Floppy diskettes were inexpensive and easy to handle. They are becoming somewhat overshadowed by today's technology of CD-ROM, ZIP, and JAZ drives.

Floppy disk drives are used to "read stored information" from a magnetic encoded disk, and copy this information into the computer's memory (RAM) so it can be used by the computer. A Floppy disk drive is also used to "write" information from the computer's memory onto a disk so it can be stored for later use.

  • We often must tell the computer which drive has the disk with the information we want or where to send the information. For this reason, each disk drive is assigned a letter or number.

  • Floppy and Hard Disks operate in a similar way that a common audio cassette tape operates. We record (Save) something we have created like a letter onto the disk.

  • Then, hours, days, or months later we can play back (Retrieve) the document into the computer to alter or print it out. Just like cassettes, the Floppy and Hard Disks do not require electricity to retain their information.

  • Floppy and Hard Disks are called nonvolatile memory because they will retain their information without the aid of electricity.

Floppy disks differ in size as well as in the amount of information they can store. The amount of information (called capacity) is measured in kilobytes (abbreviated K) or in megabytes (abbreviated M). One byte equals about one typed character.

One kilobyte equals around 1 thousand bytes (1024 to be exact), and one megabyte equals around 1 million bytes (typed letters or characters.)

There are basically two popular sizes of floppy drives in use today, with two additional sizes introduced in recent years.

5 1/4-inch disks - These are in a flexible jacket. Due to its limited storage capacity, the 5 1/4 inch Floppy Drive is no longer found on most modern computers. However, you may see them on some of the older 486 and below systems. The disk typically were available in several capacities ranging 360K to 1.2 Mb.

    • Originally, 5 1/4 Inch floppies had 1 side and 185 KB space, they later were formatted at 360KB, and even later, you could format for 1.2Mb.

    • The 360k disks were often called double-density-double sided (DD) These disks could store around 360,000 characters of information. Double-sided means that both sides of the disk stores information.

    • The 1.2mb disks were often called double-sided-high-density (HD). This disk could store about 1.2 million characters.

    3 1/2-inch disks - The 31/2 inch floppy is still in use today. Even though these disks are encased in a rigid jacket, they are still considered floppy Disks.
      • In the early days disks were generally blank when you purchase them. (A few companies sold pre-formatted disks.) To prepare a disk for use, you had to run the DOS format program. Most disks sold today are already formatted.

      • These floppies could be formatted at 720 KB (DD2S), 1.2 MB, and 1.44 MB. In some instances, they have been specially formatted at 1.68 MB and 1.72 MB; however, without special software you cannot format at these levels.

      • These 3.5 inch floppies are excellent for small file portability; however, today, many graphics images alone are larger than the 1.44MB. If you need to carry many large files, they require multiple floppies which become cumbersome to handle.

      How do They Work?
      Notice the disk case is hard, but inside the case, there is a flexible disk called a "platter" or a surface. There are normally two surface on a single platter in a floppy drive. The Read/Write head is on the robot arm that extends over the surface.

      The platter on a floppy diskette drive are coated with some magnetic film material that can record data in the form of magnetized spots on the surface.

      The disk surface has "tracks" that are concentric circles (complete circles) that are next to each other on each surface. The tracks on the outside are larger than the tracks on the inner part of the surface. There may be 200 or more tracks per surface.

      Then each surface is subdivided into "sectors". Each sector on each surface will be able to contain a specific amount of bytes (8 bit characters), usually 512 bytes per sector.

      The size of the sector determines the amount of data that can be written, and the amount that will be wasted if only a few characters are in a record. A one byte record written to a sector occupies the entire track in that sector.

      A floppy diskette must have a record that defines the disk to the CPU for access/writing. In a DOS environment, this record is the File Allocation Table (FAT). The speed of rotation is a factor in the access speed of the drive.

      The read/write head must move to the proper track before it can read. Once at the proper track, it must wait for the proper sector to rotate under the head to read the data. This is called the "latency" time.

      The more files you have on a diskette, the larger the FAT table. Consequently, if you have a large number of files on the floppy, the less actual data you can put on the drive, for example, with one file on a floppy, you can put almost 1.44MB of data; for 250 files, you might only be able to put 1.2 MB of data on the same diskette!

      Protecting Floppy Disks

      Because floppies are portable, certain precautions should be taken to protect them from the hazards of transportation.

      • The Sun -Always store floppies away from sunlight and heat.

      • Magnets - Keep them away from stereo speakers and telephones (the magnets in these devices can erase part or all of the disk).

      • Touch - Never touch the Mylar surface.

      • Bending - Do not bend the disks Always store in their protective sleeve Hold the disk by its label or any part of the sleeve.

      • Heat - Do not leave in hot or cold areas (radiators, car dash, in car during winter or summer)

      • Writing - Use felt tip pens if possible when labeling. Ball point pens can crease the mylar surface of a 5-1/4 inch disks.