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Chapter: 3.7 Drives

Topic: 3.7.1 Drives

Drives

 Drives are logical partitions of the hard disk or may be extension to the hard disk.
 A convention is followed while giving names to these partitions. For example, A:,
B: represents Floppy disk. C:, O:, E: represents Hard Disk, and F:, G: represents
the Compact Disk.
 To switch from one drive to another, only the drive letter followed by a colon
needs to be specified. For example, at C:\> type A: and press <Enter>. This will
take you to A:
 While doing any directory or file manipulation user must take note of your
location.
 Location of a file or directory always starts with the drive letter (which is the root)
followed by the name of its parent in one order and finally its own name.
 For example, C:\Program Files\Microsoft Office\Office\MS Word
 Implies that the root is C:\, one of the folders in C:1 is Program Files, Program
Files contains Microsoft Office folder, which in turn contains office folder, which in
turn contains MS Word.

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Chapter: 3.4 Command prompt

Topic: 3.4.1 Command prompt

Command prompt

 Command Prompt is a command line interpreter application available in most

Windows operating systems.
 The Command Prompt program allows the user to work in an environment that
looks more like a traditional operating system as opposed to the icon based
Windows environment.
 Command Prompt is officially called Windows Command Processor but is also
sometimes called the command shell or by its file name cmd.exe.
 In Command Prompt, only keyboard can be used and mouse cannot be used.
 Command Prompt works at a lower level than Windows. This means that user
will have more control over the machine.
 The disadvantage of command prompt is that it is not user-friendly.
 The GUI based operating system made command prompt boring.

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Opening a command prompt:
 There are two conventional ways to start a Command prompt.
 Start->Programs-> Accessories->Command prompt
 Start->Run and type "cmd" and press enter.
 The Command Prompt shows up as a black terminal window. The command
prompt should look something like: C:\>

FIG 3.62: Command prompt

Directory Navigation

 Navigating the command prompt, as well as changing drives and directories is

important skill to have. To do this, you must learn a few commands that you must
enter into the command prompt.
 Changing directories (or changing your path) in the command prompt makes use
of the CD command. The CD command has a small amount of possible
arguments. CD accepts a drive and a path.
 Some of the key commands are:
 CD ( Change Directory) : The CD command is very simple to use. All
commands are relative to the directory that you are in. Therefore, using the
example output of a "dir" that is shown above, if you want to change to the
"Windows" directory, you would type

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 CD Windows : If you want to change to the "system" directory (which is a sub
directory of "windows"), you would enter
 CD System : However if you knew that you wanted to change to the system
directory immediately, you could type this command.
 CD Windows\System : However if you were already deep in another
directory (for example c:\ documents and settings \username\ local settings)
and then wanted to move directly to windows\system then you can do that by
putting in an initial backwards slash.
 CD \Windows\System : This tells the command to go to the root of the drive,
then to the directory Windows and system.
 Moving Back Up : You can also move back up the tree, instead of down.
 cd \ or cd\ : to just return to the root of the drive (C:\)
 cd.. : to just go back one level (to use the earlier example, you were in
c:\windows\system and you wanted to be in c:\windows).
 cd program files or cd "program files" : to access a totally different
directory, for example "Program Files". When typing directories to change to,
if the directory name is unique, then you can use wild cards. For example : cd
program.
 dir - This command will list all of the folders and files in the directory you are
currently at.
 cd folder - This command will move you to the folder that you specify. The
folder must be in the directory you are currently in. For example: If you are
currently at C:\Users\username\ and you enter cd desktop you will be taken
to C:\Users\username\Desktop\
 cd path - This command will take you to a specific path on your computer.
You do not need to be in the same directory as the path. You must enter the
entire path for it to work. For example: cd C:\Windows\System32
 driveletter: - This command will take you to the drive letter that you specify.
The drive you specify will need to be active, or have a disc in it if it a CD\DVD
drive. For example, if you want to switch to your D drive, you would enter the
command D:

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 exit - This command will exit the Command Prompt, no matter your current
location.

Path setting:

 Users can run an executable from windows command prompt either by giving the
absolute path of the file or just by giving the executable file name.
 In the latter case, Windows searches for the executable in a list of folders which
is configured in environment variables. These environment variables are as
below.
1. System path
2. User path.
 The values of these variables can be checked in system properties( Run
sysdm.cpl from Run or computer properties).
 Initially user specific path environment variable will be empty. Users can add
paths of the directories having executables to this variable.
 Administrators can modify the system path environment variable.

To set path from command line

 In Vista, Windows 7 and Windows 8 we can set path from command line using
‗setx‘ command. setx path "%path%;c:\directoryPath"
 For example, to add c:\dir1\dir2 to the path variable, we can run the below
command. setx path "%path%;c:\dir1\dir2"
 Alternative way is to use Windows resource kit tools ‗pathman.exe‗. Using this
command we can even remove a directory from path variable.

1. System path environment variable:

 Open administrator command prompt and Run the below command
 To add directory to the system path environment variable.
 Syntax : pathman /as directoryPath

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 To remove path from system path environment variable.
 Syntax : pathman /rs directoryPath

2. Setting user path environment variable

 For user environment variables, admin privileges are not required. We can run
the below command to add and remove a directory to user path environment
variable.
 To add a directory from user path, user can run the below command.
 Syntax : pathman /au directoryPath
 To remove a directory from user path, user can run the below command.
 Syntax : pathman /ru directoryPath

Creating And Using Batch File

 A script or text file which contains a series of commands to be executed by the

command interpreter is called as batch files.
 Batch files are created to automate frequently performed tasks.
 A batch file may have any constructs that enables conditional branching and
looping within the batch files.
 Batch files are simply text files, which is created using Windows notepad
application. It should be created only using notepad, Other word processing
applications should not be used as they stores the files by adding their own
formats.
 Batch file is created by typing the command to run, in a text file and saving with
the .BAT extension.

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Chapter: 3.5 Files

Topic: 3.5.1 Files

Files
 Files are logical containers of data that are always present at the leaf level of a
directory tree, i.e., they are the last element of any tree.
 A file cannot be a collection of other files or directories and can only contain
data or instructions.
 Each file has a set of properties associated with it, such as
 Size
 Date created
 Date accessed
 Date modified
 Path
 File name

 File name
 Each file is recognized by its filename. Filename has two parts; name and
extension. File naming conventions must be followed while naming a file. A
filename can have a maximum of 8 characters.
 Extension identifies the type of the file or the application to which a particular
file belongs. It can be 3 characters long.
 Size
 Size determines how much space the file is occupying on the disk.
 Date created
 Data created corresponds to the date when file was created.
 Date accessed
 Data accessed corresponds to the date when file was last accessed.
 Date modified
 Data modified corresponds to the date when file was last modified.

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 Path
 Path specifies the location of file on the disk. It comprises of a series of
predecessor (parent) directories and moves up to the root.
 A file has a certain defined structure which depends on its type
 Text file
 Source file
 Object file
 Executable file
 Text file
 Sequence of characters organized into lines.
 Source file
 Sequence of sub routines and functions each of which is further organized as
declarations followed by executable statements.
 Object file
 Sequence of bytes organized into blocks understandable by the system's linker
 Executable file
 Series of code sections that the loader can bring into memory and execute.

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Chapter: 3.6 Directories and its Structure

Topic: 3.6.1 Directories and its Structure

Directories and its Structure

 Directories are a collection of files or other directories.
 Directory at the highest level is called the root directory.
 There can be only one root in a directory structure.
 Directories at lower levels are called child and those who share the same parents
are called siblings.
 A directory structure can be viewed as a way to organize files on the hard disk.

FIG 3.63: Directory Structure

Operations on a directory

 The directory can be viewed as a symbol table that translates file names into
their directory entries.
 The operations that can be performed on the directory are:
 Search for a file
 Find the entry for a particular file.
 Create a file
 Create new file and add to directory.
 Delete a file

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 Remove a file when no longer needed.
 List a directory
 List the files in a directory and the contents of the directory entry for each file
in the list.
 Rename a file
 Change name of a file as per user‘s request.
 Position within the directory may also change.
 Traverse the file system
 Every directory and every file within a directory structure should be
accessible.
 Magnetic tape is the commonest backup device.
Directory Structure
 The directory structure is the organization of files into a hierarchy of folders.
 It should be stable and scalable; it should not fundamentally change, only be
added to.
 Types of directory structure
 Single-level directory
 Two-level directory
 Tree structured directory
 Acyclic graph directory
 General graph directory
Single-level directory
 A single-level directory with file entries for all users contained in the same
directory.
 It is the simplest structure of all directories.
 All files are in the same directory.
 It is easy to support and understand.
 Name collision problem - files must have unique names since multiple users
share same directory.

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 Even in case of a single user it is difficult to remember all file names and create
files with unique names (the naming problem).
 Files are limited in length.

FIG 3.64: Single-level directory

Two-level directory
 The standard solution to limitations of single-level directory is to create a
separate directory for each user.
 System maintains a Master File Directory (MFD).
 A separate directory for each user.
 Easy to support and understand.
 User file directory (UFD).
 User name and a file name constitute a path name.
 Solves the name collision problem.
 Sharing of files by different users is difficult.

FIG 3.65: Two-level directory

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Tree structured directory
 The two-level directory structure can be extended to a tree of arbitrary height.
 Tree is the most common directory structure.
 Examples of systems supporting tree structure.
 MS-DOS
 UNIX
 A tree has a root directory.
 The root contains a set of directories.
 A directory contains a set of files and other sub directories.
 Each sub directory can further contain a set of files and other sub directories.
 Each file has a unique path name.

FIG 3.66: Tree-structured directory

 One bit in each directory entry defines the entry as a file(0) or as a sub
directory(1).

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Path name

 A path name is the path from the root, through all the subdirectories, to a
specified file.
 Example
 In the figure root/spell/mail/prog/obj is a path.
 Types of path names can be of two types.
 Absolute path name.
 Relative path name.
 Absolute path name
 An absolute path name begins at the root and follows a path down to the
specified file giving the directory names on the path.
 Relative path name
 A relative path name defines a path from the current directory.
 With reference to figure, if the current directory is root/spell/mail, to reference the
file list.
 Relative path name: prog/list.
 Absolute path name: root/spell/mail/prog/list.

Acyclic graph directories

 When the same files need to be accessed in more than one place in the directory
structure ( e.g. because they are being shared by more than one user / process ),
it can be useful to provide an acyclic- graph structure
 UNIX provides two types of links for implementing the acyclic-graph structure.
 A hard link (usually just called a link) involves multiple directory entries that
both refer to the same file. Hard links are only valid for ordinary files in the
same file system.
 A symbolic link, that involves a special file, containing information about
where to find the linked file. Symbolic links may be used to link directories
and/or files in other file systems, as well as ordinary files in the current file
system.

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FIG 3.67: Acyclic graph directory

General graph directories

 Allow users to create subdirectories in a two-level directory result is a tree

structured directory.
 Simply adding new files and subdirectories to an existing tree-structured directory
preserves the tree-structured nature.
 When user add links to a tree, the tree structure is destroyed resulting in a simple
graph.
 Cycles allowed.
 Cycles might result in an infinite loop while searching.
 One solution is limit to the number of directories which will be accessed during a
search.

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FIG 3.68: General graph directory

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