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Chapter 4

Chapter 4. Floppy Drives and Other Essential Devices. Managing and Maintaining Your PC. Floppy Drives. 5 1/4” drives Double-density and high-density 3 1/2” drives - More prevalent than 5 1/4” Hold more data than 5 1/4” Double-density, high-density, and the very rare extra-high-density.

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Chapter 4

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  1. Chapter 4 Floppy Drives and Other Essential Devices Managing and Maintaining Your PC

  2. Floppy Drives • 51/4” drives • Double-density and high-density • 3 1/2” drives - • More prevalent than 5 1/4” • Hold more data than 5 1/4” • Double-density, high-density, and the very rare extra-high-density

  3. Floppy Drives Table 4-1 Floppy Disk Types

  4. Floppy Drives • The physical hardware of all disk drives looks and operates in much the same way: • Data cable connects the drive to a controller board (or to the systemboard) • Controller board plugs into the system bus • The board communicates with the CPU, passing data to and from the floppy disk • Power is provided by the power supply

  5. Floppy Drives Figure 4-1 Floppy drive, data cable, and power connection

  6. Floppy Drives • All floppy disks store data in much the same way • Diskettes start out as blank disks of magnetically coated plastic • Before data can be written to the disk, it must be formatted: • It is mapped out in concentric circles called tracks or cylinders • The tracks are divided into pie-shaped wedges called sectors

  7. Floppy Drives Figure 4-2 3 1/2-inch disk showing tracks and sectors

  8. Read/Write Heads • Data is written to and read from the disk via read/write heads • Read/write heads are basically a magnetic mechanism in the floppy drive • An actuator head holds 2 read/write heads - one head is above the disk, the other is below • As the disk spins, the heads lightly touch the disk’s surface

  9. Read/Write Heads Figure 4-3 Uniform track widths are created by a floppy drive read/write head

  10. Disk Storage • Sector - The segment of a track that falls within the pie-shaped wedge • Holds 512 bytes of data • Cluster - one or more sectors that are the smallest units allocated for a file • The smallest unit of data that can be read from or written to a disk at on time • Sometimes called fileallocationunits

  11. Formatting Disks • Formatting: • Creates tracks and sectors by writing a series of F6s, (which effectively erases any data on the disk), and sector address marks to identify the beginning sector on a track • Creates the master boot record • Creates 2 copies of the file allocation table (FAT) • Creates the root directory

  12. Formatting Disks - MBR • Master boot record contains information that DOS later uses when it reads from the disk • When the disk was formatted • How the disk was formatted • What version of DOS or Windows 95 was used • Contains a uniform layout • Located at track 0, sector 1

  13. Formatting Disks - MBR Table 4-2 Contents of the Master Boot Record

  14. Formatting Disks - FAT • File allocation table (FAT) • Contains location of files on the disk • Lists how each cluster or file allocation unit on the disk is currently being used • Files may be in one or more clusters that may not be contiguous on the disk (Noncontiguous files are “fragmented files”) • Cluster chain determines all cluster locations for a file on a disk

  15. Formatting Disks - FAT Figure 4-4 FAT with one file mapped on the disk

  16. Formatting Disks - Root Directory • Root directory • A table listing all the files that are assigned to this table • Contains a fixed number of rows, dependent upon the disk type • Contains information about each file and subdirectory stored in it • Only directory that limits the number of entries

  17. Formatting Disks - Root Directory Table 4-3 Root Directory Entries for Disk Types

  18. Formatting Disks - Root Directory Table 4-4 Root Directory Information for Each File

  19. Formatting Disks - Root Directory Table 4-5 File Attributes for each Bit in the Directory Attribute Byte (Reading from Left to Right Across the Byte)

  20. Managing Disks using DOS • FORMAT command • Prepares a disk for use • LABEL command • Changes the volume label or electronic name on a disk • CHKDSK command • Creates a status report of a disk and also reports on free conventional memory • Can repair lost clusters in the FAT

  21. FORMAT Command FORMAT Options DESCRIPTION /V To enter Volume label /S Writes System files to disk /Q Quickly reformat a good disk /F:size Specifies size of disk if not default Ex: FORMAT A:/F:720 /U Unconditional or complete format Table 4-6 FORMAT Command Options

  22. Managing Disks using DOS • SCANDISK command • Checks for lost and cross-linked clusters, does a surface scan for bad sectors, and may defragment the drive • DEL or ERASE command • Erases files or groups of files • UNDELETE command • May be used to try to recover deleted files on a disk area that has not be overwritten

  23. Managing Disks using DOS • RECOVER command • Attempts to recover a file from damaged sectors on a disk • DISKCOPY command • Makes an exact duplicate of one disk to another disk of the same size and type • COPY command • Copies a single file or a group of files

  24. Managing Disks using DOS • XCOPY command • More powerful than the COPY command • Can be used to copy all files in a directory, and all subdirectories under the directory • Can be used to copy files created or modified after a specified date • DELTREE command • Deletes a directory, its subdirectories, and all files within the subdirectories

  25. Managing Disks using Windows 3.x File Manager • Format a disk from the File Manager • Click the Disk menu • Click FormatDisk • Click the Capacity list arrow • Select the correct disk type • Other disk commands can be performed from the File Manager via the Disk menu

  26. Managing Disks using Windows 3.x File Manager Figure 4-5 Format a Disk from File Manager

  27. Managing Disks using Windows 3.x File Manager Figure 4-6 Disk menu in File Manager

  28. Managing Disks using Windows 3.x File Manager Table 4-7 Four Disk Menu Options Under File Manager

  29. Managing Disks using Windows 3.x File Manager Figure 4-7 File menu in File Manager

  30. Managing Disks using Windows 3.x File Manager Table 4-8 Five File Menu Options Under File Manager

  31. Managing Disks using Windows 95 • Format a disk • Click Start button on task bar • Click Programs • Click WindowsExplorer • Right-click on either drive A or drive B • Click Format on the menu • Select appropriate options

  32. Managing Disks using Windows 95 Figure 4-8 Menu to manage a floppy disk

  33. Managing Disks using Windows 95 - Copy a Disk • If you select CopyDisk • The disk listed under “Copy from” is the source disk • The disk under “Copy to” is the destination disk • Click Start to copy the disk

  34. Managing Disks using Windows 95 - Copy a Disk Figure 4-10 Copying a disk

  35. Managing Disks using Windows 95 - Rescue Disk • When you create a Windows 95 rescue disk, the disk is formatted and system files are copied to the disk • In addition to the files necessary to boot the system, the files in Table 4-9 may also be copied to the disk

  36. Managing Disks using Windows 95 - Rescue Disk FILE PURPOSE Io.Sys Used to boot DOS Msdos.Sys Startup configuration Information Command.Com Provides DOS prompt Attrib.Exe Changes the attributes of a file Chkdsk.Exe Checks status of disk and repairs Edit.Com DOS editor Fdisk.Exe Used to Partition a hard drive Format.Exe Formats a disk or hard drive Mem.Exe Displays memory information Mscdex.Exe CD-ROM driver Scandisk.Exe Checks and repairs disk drives Sys.Com Makes a diskette or hard disk bootable Table 4-9 Rescue Disk Files Created in Windows 95

  37. Problems with Floppy Drives • Over time, floppy drives may slowly shift out of alignment. With the proper software tools you can quickly check if a drive is working properly and test: • Azimuth skew - does the drive head align itself well with the tracks? • Hub centering - does the disk wobble as it turns? • Hysteresis - Can the drive find a track from any direction?

  38. Problems with Floppy Drives • Radial alignment - is the drive head centered on the track, or off to one side or the other? • Rotation speed - does the drive turn the disk at the proper speed? • Sensitivity - How far from the disk can the head be to read the data? • Floppy drives are currently so inexpensive that they are usually replaced rather than repaired

  39. Problems with Floppy Drives Figure 4-11 Alignment of floppy drive heads

  40. Problems with Floppy Drives • Suggestions for solving problems: • Reinsert the disk • Check drive for debris • Be sure the disk is in the proper drive • Try a different diskette in the drive • Try to access the disk with different software • Try the DIR and CHKDSK commands

  41. Problems with Floppy Drives • Does the drive light come on at all? It may be a hardware or software problem • If there are two drives, verify that the other drive works • Reboot the machine and try the drive again • Make sure the CMOS settings are correct • Clean the read/write heads • Check all cable connections

  42. Problems with Floppy Drives • Replace the data cable • Exchange the controller card • Exchange the drive with a working one • The problem may be with the systemboard or the ROM BIOS

  43. Floppy Drive Error Messages • Non-system disk or disk error. Replace and strike any key when ready. • You are booting from a disk that does not have the OS on it (It is missing: Command.Com, IO.Sys, MSDOS.Sys) • Invalid or missing COMMAND.COM • Boot from a disk that contains the correct version of COMMAND.COM

  44. Floppy Drive Error Messages • Incorrect DOS version • You are using external DOS commands from a different version of DOS • Invalid Drive Specification • You are trying to access a drive the OS does not know is available • Not ready reading Drive A:, Abort, Retry, Fail? • Disk is not inserted correctly; possible bad boot record, FAT errors, or bad sectors

  45. Floppy Drive Error Messages • Track 0 bad, disk not usable • Appears when you try to format a disk using the wrong disk type or size; check your FORMAT command • Write-protect error writing drive A: • Disk is write-protected. Be sure the write-protect window in the 3 1/2” disk is closed, or the write-protect notch on the 5 1/4” disk is uncovered

  46. Chapter Summary • The essential input/output devices on a computer are disk drives, keyboard, monitor, and pointing device • Floppy drives • Must be formatted before they can be used • Data is stored on disks in concentric circles called tracks • Disks come in different sizes and capacities

  47. Chapter Summary • The smallest unit of space allocated to a file is called a cluster • Command.Com and 2 hidden files must be on a disk to make it bootable • DOS, Windows 3.x, Windows 95 have similar commands to manage floppy disks • Floppy drives can be replaced or added to computers • A twist in the data cable indicates to the computer which drive is drive A

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