The Root Directory, Floppy Disk Drive And Connections, Floppy Drive Exchange And Installation

The Root Directory

After creating the file allocation tables, the formatting process sets up the root directory. Recall that the root directory, or main directory, is a table listing all the files assigned to this table. The root directory contains a fixed number of rows to accommodate a predetermined number of files and subdirectories; the number of available rows is dependent upon the disk type. The number of root directory entries for the four common disk types is listed in the table below.

Disk Type Number of Root Directory Entries

5¼- inch double-density 112

5¼-inch high-density 224

3½-inch double-density 112

3½-inch high-density 224

The root directory will later contain information about each file and subdirectory stored in it. Each directory entry is 32 bytes long, although only 22 bytes are used.

The root directory contains only the starting cluster number. To find out what other clusters store the file, look in the file allocation table. By dividing the size of the file by the number of bytes per cluster and rounding up to the nearest whole number, you can determine how many clusters the file occupies.

The root directory and all subdirectories contain the same information about each file. Only the root directory has a limitation on the number of entries. Subdirectories can have as many entries as disk space allows.

Floppy Disk Drive And Connections

The figure below shows a floppy disk drive and its connections:

1. A floppy drive is connected to either the controller card or systemboard by a 34- pin data cable.

2. The controller card plugs into the system bus in an expansion slot.

3. The card then communicates with the CPU, passing data back and forth from the floppy disk.

While older computers used a controller card to pass data to and from the floppy disk, now the controller is built right into the systemboard. However, you will still see controller cards—also called I/O cards—so you should be familiar with them.

The cable has the controller connection at one end and a drive connection at the other end. A second drive connection is placed somewhere in the middle of the cable to accommodate a second floppy drive. Having two drives share the same cable is a common practice for floppy drives as well as hard drives and CD-ROMs.

The power cable usually plugs into the back of the drive onto a board that sits on top of the drive. This board, called a logic board, is considered part of the drive.

Floppy Drive Exchange And Installation

Many computers today have one or two empty bays for a second floppy drive or for a CD-ROM drive. If you don’t have an extra bay and want to add another drive, you can attach an external drive that comes in its own case and has its own power supply.