Comm-Ls. No. 5














OLD SYLLABUS

Commerce Section

Lesson No. 5 File and Disk Utility


Short Question Answers



Explain Fragmentation.        
Write a note on Disk De-fragmentation.        
Write a note on File Names and File Icons        
Explain Encryption.        
Explain File Compression.        
Explain the two types of Compression.        
Differentiate between Fragmentation and De-fragmentation.        

Lesson No. 5 File and Disc Utility




Files and Folders
  A file, or document, is a collection of data that has a name and is stored in a computer
  A directory (folder) called stores a number of files on your disk.
Files
  A file is a collection of data or information, which has a name and is stored in the computer.
  A file also has an extension, which is mostly three letters.  E.g.  .docx,  .jpg,   .mp3
  Extension tells the type of file.

File Extension
  A filename extension is a set of characters that helps the Operating system to understand what type of data is in file and what program should open it.
  It appears at the end of the file name, followed by a period (dot).
  E.g      Myfile.docx,      marksheet.xlsx,        myphoto.jpg,      1 song.mp3,     myvideo.mp4
Image File extensions
What's The Image For?
Recommended File Type
Details
Web Buttons and Logos
PNG
Allows for compression, alpha transparency, true color and is great with straight lines and text
Web Photos
JPEG
High detail with small compression. Great with gradual color changes in regular photos
Printing Images
TIFF
No compression for highest image quality
Editing Images
PSD/XCF/CRD
Standard file type for respective programs (Photoshop, GIMP, Corel). Maintains extra data like layers and effects
Images in Documents
PDF
Maximum compatibility in sharing with extra security and saving features
Simple Web Animations
GIF
Small and simple web animations

Filename Rules
  The maximum length of the file name in Windows XP is 255 characters.
  You can’t use any of the following special characters like   <,  >, :, “, /, \, |, ?, * in a file name.
  Use letters and/or numbers for filename.
  Use uppercase or lowercase letter for file name.

Folders
  A directory (folder) called stores a number of files on your disk.
  Folders or directories can also store other directories, which may store more files or other directories and so on.
  Directory is a collection of different files and different directories.
  Directory allows people to organize all files in a way that can be easily searched.

Organizing Files and Folders
Windows organizes folders and files in a hierarchy, or file system
Windows stores the folders and important files it needs to turn on the computer in its root directory
Folders stored within other folders are called subfolders

File Archival
  A file archival is a program, which combines more than one files into one archive file for easier transportation from one computer to another or storage devices.
  The archival takes a list of files and sequentially concatenates their contents into the archival.
  It also contains information about the names and lengths of the originals for proper construction.
  Archival also stores metadata about a file, which is provided by the operating system, like as timestamps, ownership and access control.
  The process of making an archival file is called archiving or packing.
  Process of conversion of archival file in to its original format (Reconstructing the original file from the archive) is called unarchiving, unpacking or extracting.

File Compression
  Compression is the reduction in size of data or file in order to save space, transmission time for encoding data more efficiently
  Also for reduction in the number of bytes used to store the information
  Compression is done by using some compression algorithms that rearrange and reorganize data or information so that it can be stored more economically.
  For compression of data or information two different algorithms are used
  Lossless Compression and Lossy Compression

Lossless Compression
  Lossless compression reduces file size without a loss of information in the process. The original file can recreated, as it is when you uncompressed it.
  It is used to compress document file, database files, program files, etc.
  ZIP, RAR compressions are example of lossless.
  In images, PNG is lossless compression.

Lossy Compression
  Lossy compression reduces file size of a file by eliminating bits of information.
  It also permanently deletes any unnecessary data.
  This compression algorithm is usually used with image files, audio files and graphics where a loss of quality is affordable.
  THE ORIGNAL FILE CANNOT BE RETAINED.
                Example – jpg, mp3, etc

Disk Compression
  Disk Compression software utility increases the free space in the hard disk to store more data by reducing the size of files and deleting the unused space and the data, which is not frequently used.

Encryption
  Encryption is an algorithm, which gives protection for data from unauthorized people.
  It is the conversion of plain data into a cipher text or non-readable text.
  Encryption is the process to convert data into coded form.
  Encryption process is especially important in wireless communications.
  It is used in WWW for carrying out sensitive transaction such as purchasing of goods using credit-card, or transferring company’s secret document between departments.

Decryption
  Decryption is the process of converting encrypted data or cipher text back into its original form that means decoding of coded data.
  The correct decryption key is required to convert the contents of an encrypted signal.
  document between departments.


Disk Utilities
Disk Fragmentation
How does a disk becomes fragmented?
       The total free space of disk is broken into little pieces, this process is called fragmentation.
       Fragmentation is occurred when maximum, but non-contiguous memory space is available in hard disk after deleting unwanted files or programs.
       Fragmentation occurs on a hard drive, a memory module, or other media when data is not written close enough physically on the drive.
Fragmentation means two things:
       A situation when the free space on a disk scattered here and there rather than contiguous few free space. It is called as disk fragmentation. It decreases the performance of Hard disk.
       A situation when an individual program or file stored on a disk are not contiguous but are broken up in pieces scattered around the disk. This is called as file fragmentation. It causes performance problems when reading files.

Disk De-fragmentation
To reduce the amount of fragmentation, defragmentation process is used.
       It rearranges the files or programs and gives large number of contiguous free space on storage devices and increase the performance of storage device.






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