Floppy Drives

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Chapter 5

• Floppy Drives

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You Will Learn

• How data is stored on floppy disks
• How to use DOS and Windows commands to manage
  disks
• How to replace or install a disk drive

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Introduction to How Data Is Physically Stored on
a Disk
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Floppy Disk Drive and Connections
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How Data Is Physically Stored on a Disk

• Tracks
• Concentric circles of a disks surface
• Sector
• One pie-shaped segment of a track
• Almost always contains 512 bytes of data
• Formatting
• Process of preparing a new floppy disk for use by
  placing tracks on its surface to store information

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Tracks and Sectors
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How Data Is Physically Stored on a Disk
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Read/Write Head

• A sealed, magnetic coil device that moves across
  the surface of a disk to read/write data to the
  disk

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Read/Write Head
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How Data Is Logically Stored on a Disk

• Cluster
• Smallest unit of data that can be read from or
  written to a disk at one time
• Also called file allocation unit

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How Data Is Logically Stored on a Disk
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The Formatting Process

• Windows 9x or DOS FORMAT command
• Creates the tracks and sectors by writing tracks
  as a series of F6s in hex and, as necessary,
  writing the sector address mark to identify the
  beginning sector on a track
• Creates the master boot record
• Creates two copies of the file allocation table
  (FAT)
• Creates the root directory

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Creating the Tracks and Sectors

• The FORMAT command is a DOS and Windows 9x
  command that prepares a disk for use
• First step erases any data on the disk

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The Master Boot Record (MBR)

• The record written near the beginning of a floppy
  disk
• Contains information about the disk as well as
  the startup operating system programs

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The File Allocation Table

• A table on the disk that tracks the clusters used
  to contain a file

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The File Allocation Table
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The File Allocation Table
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The Root Directory

• The main directory on a disk (often represented
  as C\ on a hard drive)
• Typically contains other directories, such as
  Windows and MSOffice

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The Root Directory
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The Root Directory
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The Root Directory
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Using DOS to Manage a Floppy Disk

• Internal DOS commands
• DOS commands whose coding is contained within
  COMMAND.COM program and are therefore
  automatically loaded into memory when COMMAND.COM
  is loaded
• External DOS commands
• Stored as separate program files in DOS directory

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Other DOS Commands

• LABEL
• Changes the volume label or electronic name
• DEL or ERASE
• Erases files or groups of files
• UNDELETE
• Recovers deleted files
• RECOVER
• Attempts to recover a file from damaged sectors

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Other DOS Commands

• DISKCOPY
• Makes an exact duplicate, sector by sector, of
  one floppy disk (source disk) to another disk of
  same size and type (target disk)
• COPY
• Copies a single file or group of files
• XCOPY /M
• A faster external COPY program that can copy
  subdirectories
• DELTREE
• Deletes the directory tree