Floppy Disks

The humble floppy disk is one of the oldest recording devices used on x86 computers. (A primitive tape drive was actually used by the very first IBM PC, instead of a floppy disk, however.) Today's x86 computers almost invariably support a 3.5-inch floppy disk, but 5.25-inch disks were common as late as the mid-1990s. (Figure 6.1 shows both types of disks.) Earlier computers sometimes used 8-inch floppy disks, but these were never used on x86 hardware. The 8-inch and 5.25-inch floppy disks used flexible outer casings, hence the term floppy disk. The 3.5-inch variety incorporated a harder plastic shell, greater precision in disk mounting, and a shutter to cover the disk read/write access hole. These characteristics contributed to greater reliability and higher data densities in 3.5-inch floppies compared to earlier varieties.

Part II

Figure 6.1

Floppy disks have come in several sizes over the years. This picture depicts a 5.25-inch floppy on the left and a 3.5-inch floppy on the right.

Figure 6.1

Floppy disks have come in several sizes over the years. This picture depicts a 5.25-inch floppy on the left and a 3.5-inch floppy on the right.

Floppy disks have several important advantages as storage media for x86 computers:

• Cost Both floppy disks and their drives are inexpensive. This characteristic is particularly important when you want to send a file to somebody and you can't send it via the Internet. It's also important in shared computing environments, such as computer centers on college campuses. The low cost of floppies also means you can afford to lose or destroy a few—provided the data they contain aren't too important, or are backed up elsewhere!

• Universality Almost every desktop computer today has a 3.5-inch floppy disk drive, so you're almost guaranteed interoperability if you use floppies and a common filesystem, such as the File Allocation Table (FAT) filesystem.

• Portability 3.5-inch floppies fit into a shirt pocket, or you can pack a few into small cases or wallets designed for them and tote them around in a backpack, coat pocket, or purse without too much difficulty.

Floppy disks are an old technology, however. They simply have not kept up with increases in storage capacity and speed available on other media, both fixed and removable. These two factors—speed and capacity—constitute the floppy disk's Achilles' heel. The maximum floppy disk capacity in common use is 1.44MB, which is nothing compared to a typical hard disk in

Chapter 6

Table 6.2 Floppy Disk k k Capacities

Floppy Type Single-Sided Double-Sided

Capacity Capacity

5.25-inch, double-density 180KB 360KB

5.25-inch, high-density 600KB 1200KB

3.5-inch, double-density 360KB 720KB

3.5-inch, high-density 720KB 1440KB

3.5-inch, extra-high-density 1440KB 2880KB

Almost all floppies are double-sided, although a few very old systems used single-sided floppies.

2000, the capacity of which can be more than 10,000 times greater than the floppy s. Floppy disks are also notoriously slow, a fact which is mitigated merely by the low capacity of the medium. Table 6.2 summarizes the capacities available on floppy disks today. Note that, although double-sided high-density 1.44MB floppies are the largest in common use, they're not the highest capacity available. The higher-capacity 2.88MB floppies never caught on, and are nearly impossible to find today. Single-sided floppies use only one side of the disk to record information, whereas double-sided drives use two read/write heads to record on both sides of the disk medium.

In addition to the capacities outlined in Table 6.1, a number of non-standard capacities exist. Various floppy disk formatting programs let you place more sectors on each cylinder, or put more than the usual number of cylinders on a disk. Both methods increase the capacity of the floppy, but at the cost of reliability and interoperability—some systems can't read such nonstandard floppy formats.

Most floppy disk drives interface through the floppy port on the motherboard, but a few USB-interfaced floppy drives are available. These are marketed primarily to Macintosh users, because some Macintoshes (notably the iMac) come without a floppy drive.

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