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Chapter 5 Introduction to Hard Drives Managing and Maintaining Your PC Chapter 5A - Introduction to Hard Drives MENU Disk Organization FAT, DEBUG, VFAT, root dir Using DOS to manage drives Using Windows 3.X to manage drives Using Windows 95 to manage drives

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chapter 5
Chapter 5

Introduction to Hard Drives

Managing and Maintaining Your PC

chapter 5a introduction to hard drives
Chapter 5A - Introduction to Hard Drives

MENU

Disk Organization

FAT, DEBUG, VFAT, root dir

Using DOS to manage drives

Using Windows 3.X to manage drives

Using Windows 95 to manage drives

hard drives physical organization
Hard Drives - Physical Organization
  • Modern hard drives have two or more platters, or disks, that are stacked together and spin in unison
  • Read/write heads are controlled by an actuator and move in unison across the disks’ surfaces as the disks rotate on a spindle
  • Data is stored in tracks and sectors
hard drives physical organization4
Hard Drives - Physical Organization

Figure 5-1 Inside a hard drive case

hard drives physical organization5
Hard Drives - Physical Organization
  • Each side of a platter is called a head
  • Each head is divided into tracks (or cylinders) and subdivided into sectors
  • The entire first cylinder is filled before the read/write heads move inward to the next cylinder
hard drives physical organization6
Hard Drives - Physical Organization

Figure 5-2 A hard drive with four platters

hard drives logical organization
Hard Drives - Logical Organization
  • To the OS, data is stored in a long list of clusters that are organized into files
  • The OS uses 2 tables to keep track of which clusters are being used for a file along with other file information such as filename, file length, and whether the file is read-only or a hidden file
  • The physical location of the file is tracked by the BIOS or device driver
hard drives logical organization8
Hard Drives - Logical Organization

Figure 5-3 How the operating system views the

hard drive when managing a file

hard drives partitions
Hard Drives - Partitions
  • The OS can partition the single physical hard drive into more than one logical drive, or partition
    • A logical drive is a portion of a hard drive that an OS views as and manages as an individual drive
    • Information about the logical divisions is stored in the partition table at the beginning of the drive
hard drives partitions10
Hard Drives - Partitions
  • When the drive is partitioned, the OS assigns a drive letter to the first partition, usually C
  • FDISK first creates a partition, then assigns drive letters to each logical drive and creates a boot record, FAT, and root directory for each logical drive
hard drives partitions11
Hard Drives - Partitions

Figure 5-4 A single physical drive can be viewed by

the operating system as one or more logical drives

drive capacity
Drive Capacity
  • The number of sectors present on the drive determines the drive capacity
  • All sectors in a track hold 512 bytes
  • Most earlier drives had 17 sectors per track
  • Most drives today have more than 26 sectors per track
  • #tracks * #sectors/track * 512 = capacity
translation
Translation
  • Translation converts the addressing of sectors when the hard drive addressing system does not conform to what System BIOS expects
  • Translation is required:
    • When a drive uses zone bit recording
      • Does not use the same number of sectors per track throughout the drive
    • On large-capacity drives
zone bit recording
Zone Bit Recording

Figure 5-5 Floppy drives and older hard drives use a

constant number of sectors per track

zone bit recording15
Zone Bit Recording

Figure 5-6 Zone bit recording can have more sectors

per track as the tracks get larger

large capacity drives
Large-Capacity Drives
  • Drives that exceed 1,024 cylinders and more than 528MB are “large capacity” and require an EnhancedBIOS
  • BIOS supports a hard drive as:
    • CHS (Cylinders, Heads, Sectors) or normal mode
    • Large mode (504MB to 1G), translation
    • LBA (Logical Block Addressing) mode
chs or normal mode
CHS or Normal Mode
  • Cylinders, heads, sectors (CHS) mode is the traditional method used by BIOS to read from and write to hard drives by addressing the correct cylinder, head, and sector
  • Requires no translation
  • Limited to 1,024 cylinders, 16 heads, and 63 sectors per track
  • Maximum drive capacity of 504MB
large mode
Large Mode
  • Large mode supports drives with a capacity from 504MB to 1 GB
  • A translation method
    • The location of the data on the drive is remapped to conform to the 504MB barrier
    • Then the address information is passed to the OS
    • A CMOS setting for this mode often reads either “large mode” or “translation”
enhanced bios or lba mode
Enhanced BIOS or LBA Mode
  • Logical block addressing (LBA) is a translation method similar to the FAT
  • It sends an LBA number to the OS, which is correlated with a particular cylinder, head, and sector number
  • LBA 0 stands for cylinder 0, Head 0, and sector 1
  • The OS views the drive as a long list of LBAs
when bios does not support large capacity drives
When BIOS Does Not Support Large-Capacity Drives
  • If you want to install a large-capacity drive on a PC whose BIOS does not support it, you can
    • Upgrade the BIOS
    • Upgrade the entire system
    • Use software that interfaces between the old BIOS and the new drive
      • Some drives come with disk manager software already installed
file allocation table
File Allocation Table
  • The OS manages files on the hard drive using the FAT and a 2nd FAT copy
    • FAT contains one entry for each cluster
    • A file is stored in one or more clusters
  • How to determine the size of a cluster
    • Use the CHKDSK command
    • Use DIR to see how much disk space is available, create and save a one-character file, use DIR again to see the difference
file allocation table22
File Allocation Table

Figure 5-7 FAT showing two files

debug utility
DEBUG Utility
  • DEBUG is a utility in DOS and Windows 95 that displays the hexadecimal values of the FAT and other areas of the hard drive
  • It is an editor
  • It can look at any sector on the hard drive or disk
  • It is a valuable aid for recovering data on a damaged disk or hard drive
debug utility24
DEBUG Utility

Table 5-1 Notepad and DEBUG are both Editors

debug utility25
DEBUG Utility
  • These DEBUG instructions created the memory dump on the next slide:

C:\>DEBUG Execute DOS DEBUG

-L9000:0 2 1 1 Load into memory addresses beginning with 9000 from drive 2 (drive C), starting with sector 1

and reading 1 sector

-D9000:0 Dump or Display the contents of memory starting at 9000

debug utility26
DEBUG Utility

Figure 5-8 Beginning of a FAT on a hard drive

debug utility27
DEBUG Utility

Figure 5-9 Second copy of FAT

virtual file allocation table
Virtual File Allocation Table
  • The VFAT helps Windows 95 accommodate long filenames
    • The filename and extension are stored in the root directory or a subdirectory list
    • Each entry is 32 bytes long, called a block
    • Long filenames require more than one block in the directory
    • When the OS allocates blocks for long names, it stores the information in the VFAT
virtual file allocation table29
Virtual File Allocation Table
  • The VFAT records how many blocks are allocated to each file listed in the directory
  • It is a variation of the DOS 16-byte FAT
  • It is a virtualized 32-bit FAT; that is, it is not a real 32-bit FAT
  • Some DOS-based utility programs can damage the VFAT entries
    • The DEL command can leave the extra blocks for long filenames unavailable for later use
    • SCANDISK can recover these blocks, however
root directory
Root Directory
  • The layout of the root directories for hard drives is the same as that for floppy disks
    • Total number of bytes for each file is 32
    • Date and time are stored as integers
  • The OS creates the root directory when it formats the drive
    • Has a fixed number of entries
    • Immediately follows 2nd copy of the FAT
root directory31
Root Directory

Table 5-2 Root Directory Information for each File

root directory32
Root Directory

Table 5-3 File Attributes as Listed in the Directory

Attribute Byte

(Reading from left to right across the byte)

root directory33
Root Directory

Figure 5-10 A root directory

root directory34
Root Directory

Table 5-4 Example of FAT Entries for First Two Files

in Root Directory

using dos to manage hard drives subdirectories
Using DOS to Manage Hard Drives - Subdirectories
  • MKDIR (MD) command - creates a subdirectory within a directory
    • MD C:\GAME creates a parent directory named GAME on drive C
    • MD C:\GAME\CHESS creates a subdirectory named CHESS under the \GAME directory
using dos to manage hard drives subdirectories36
Using DOS to Manage Hard Drives - Subdirectories

Figure 5-11 DIR of the \GAME directory

using dos to manage hard drives subdirectories37
Using DOS to Manage Hard Drives - Subdirectories

Figure 5-12 Dump of subdirectory table C:\GAME

using dos to manage hard drives chdir
Using DOS to Manage Hard Drives - CHDIR
  • CHDIR (CD) command - changes the current default directory
    • CD C:\GAME\CHESS Moves you into the CHESS subdirectory of \GAME
    • C:\GAME\CHESS> CD.. Moves you from the child directory CHESS to its parent directory GAME
using dos to manage hard drives rmdir
Using DOS to Manage Hard Drives - RMDIR
  • RMDIR (RD) command - removes the named directory
  • The directory must not contain any files or subdirectories
  • The directory must not be the current directory
    • RD C:\GAME\CHESS Removes the CHESS subdirectory of \GAME
using dos to manage hard drives deltree tree
Using DOS to Manage Hard Drives - DELTREE & TREE
  • DELTREE command - deletes a directory and all its subdirectories
    • DELTREE C:\GAME deletes the directory GAME and any subdirectories it contains
  • TREE command - displays the directory structure of a hard drive or disk
    • /A option specifies test
    • /F option includes filenames in the list
using dos to manage hard drives attrib
Using DOS to Manage Hard Drives - ATTRIB
  • ATTRIB command - Displays or changes the read-only, archive, system and hidden attributes assigned to files
    • ATTRIB +H filename Hides a file
    • ATTRIB -H filename Unhides a file
    • +R and -R options change the read-only status (+R prevents changes or deletes)
    • +A and -A options turn the archive bit on and off, respectively
using dos to manage hard drives mirror
Using DOS to Manage Hard Drives - MIRROR
  • MIRROR command - Saves partition table information to a disk
    • MIRROR /PARTN
  • UNFORMAT command - Reverses the effect of an accidental format and repairs any damage to a partition table that has been previously saved with the MIRROR command
    • UNFORMAT C: and UNFORMAT /PARTN
using dos to manage hard drives batch files
Using DOS to Manage Hard Drives - Batch Files
  • If you have a list of DOS commands that you will want to execute several times, you can save the list of commands in a batch file with the extension .BAT
    • Example of a short .BAT file:

C:

CD\UTILITY\TOOLS

COPY *.* A:

using windows 3 x to manage hard drives
Using Windows 3.x to Manage Hard Drives
  • Windows 3.x File Manager performs most of the hard drive management tasks
    • When you first enter File Manager, you will probably see only the directories under the root directory
    • To see their subdirectories, click or double-click the directory name
    • From File Manager, Click File menu to see a list of file management functions
using windows 3 x to manage hard drives45
Using Windows 3.x to Manage Hard Drives

Figure 5-13 File menu in File Manager of

Windows 3.1

using windows 3 x to manage hard drives46
Using Windows 3.x to Manage Hard Drives
  • To create a new directory from File Manager
    • Click File menu
    • Click Create Directory
    • Enter the name of the directory, following the same rules as for creating a directory in DOS
    • Click OK
using windows 3 x to manage hard drives47
Using Windows 3.x to Manage Hard Drives

Figure 5-14 Creating a directory in Windows 3.1

using windows 3 x to manage hard drives48
Using Windows 3.x to Manage Hard Drives

Figure 5-15 A new directory called chess is created

under \GAMES

using windows 3 x to manage hard drives49
Using Windows 3.x to Manage Hard Drives
  • To delete a directory from File Manager
    • Click the name of the directory
    • Press the delete key
    • If the correct directory has been selected for deletion, click OK
using windows 3 x to manage hard drives50
Using Windows 3.x to Manage Hard Drives

Figure 5-16 Deleting a directory

using windows 3 x to manage hard drives51
Using Windows 3.x to Manage Hard Drives
  • File Properties in File Manager is similar to the DOS ATTRIB command
  • To display the properties of a file
    • Click the name of the file
    • Go to File menu and select Properties
    • The Properties box appears
    • You may make changes to the attributes
    • Click OK to save any changes or Cancel to exit without making changes
using windows 3 x to manage hard drives52
Using Windows 3.x to Manage Hard Drives

Figure 5-17 The properties of a file

using windows 95 to manage hard drives
Using Windows 95 to Manage Hard Drives
  • Windows 95 Explorer is the primary tool for managing files on the hard drive
  • To open Explorer
    • Click Start
    • Click Programs
    • Click WindowsExplorer, or
    • Right-click MyComputer
    • Select Explorer
using windows 95 to manage hard drives54
Using Windows 95 to Manage Hard Drives
  • To create a new folder in Explorer
    • Click the name of the folder within which the new folder will go
    • Click the File menu
    • Select New
    • Select Folder; a folder will be created with the name New Folder
    • Click the folder name and change its name
using windows 95 to manage hard drives55
Using Windows 95 to Manage Hard Drives

Figure 5-18 Create a new folder

using windows 95 to manage hard drives56
Using Windows 95 to Manage Hard Drives

Figure 5-19 Edit the new folder’s name

using windows 95 to manage hard drives57
Using Windows 95 to Manage Hard Drives
  • To delete a folder from Explorer
    • Right-click the folder
    • Select Delete from the menu
    • A confirmation box will appear
    • If you have selected the correct folder for deletion, respond Yes
    • The folder and its contents will be placed in the RecycleBin
    • The disk space has been freed
using windows 95 to manage hard drives58
Using Windows 95 to Manage Hard Drives

Figure 5-20 Delete a folder in Windows 95

using windows 95 to manage hard drives59
Using Windows 95 to Manage Hard Drives
  • To view and change file attributes from Explorer
    • Right-click a file
    • Select Properties from the menu
    • The Properties box appears
    • You may make changes to the attributes
    • Click OK to save any changes or Cancel to exit without making changes
using windows 95 to manage hard drives60
Using Windows 95 to Manage Hard Drives

Figure 5-21 Properties of a file in Windows 95

managing hard drives
Managing Hard Drives
  • The PATH command works the same in DOS, Windows 3.x, and Windows 95
  • If you have an AUTOEXEC.BAT in your root directory, Windows 95 reads the PATH command in that file
  • If you do not have an AUTOEXEC.BAT file, Windows 95 uses the path

C:\Windows;C:\Windows\Command

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