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Cd Rom


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Cd Rom

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  2. 2. CD-ROM<br /> By<br />Sadaf Khan<br />Javaria Khalid<br />SumayyahIfra<br />
  3. 3. Index<br />Storage devices.<br />Categories of storage devices.<br />CD-ROM.<br />Structure of CD-ROM.<br />Reading of CD-ROM.<br />Pits & Lands.<br />Reading Speed.<br />Writing of CD-ROM.<br />File System.<br />Tracks & Sectors.<br />Writing Methods.<br />03<br />
  4. 4. Storage Capacity.<br />Advantage of CD-ROM<br />Disadvantages of CD-ROM<br />Summary.<br />References.<br />Question & Answer Session<br />04<br />
  5. 5. The storage devices store data –even when the computer is turned off.<br />It is used to keep important data and files which are of regular use on permanent basis.<br />Storage Devices<br />05<br />
  6. 6. Categories of Storage Devices<br />The two main categories are magnetic storage and optical storage.<br />Optical Storage<br />Magnetic Storage<br />06<br />
  7. 7. CD-ROM<br />CD-ROM stands for compact disc read-only memory. It is an optical disc used to store digital data, originally developed for storing digital audio.<br />
  8. 8. CD Structure<br />A CD is flat, round, portable metal disc, which is coated with a thin metalor plastic or other material that is highly reflective. <br />It is usually 0.75 inches in diameter and less than one-twentieth of an inch thick.<br />08<br />
  9. 9. Reading Data On CD-Rom<br />
  10. 10. Reading data from CD-ROM<br />A CD-ROM drive reads digital data from a spinning disc by focusing a laser on the disc’s surface.<br />Some areas of the disc reflect the laser light into a sensor, and other areas scatter the light.<br />10<br />
  11. 11. Pits and lands<br />The CD-ROM holds digital data.<br />Data is stored in the form of lands and pits.<br />Lands are flat areas on the metal surface.<br />Pitsare depressions or hollows. <br />11<br />Reading logic ‘1’<br />Reading logic ‘0’<br />
  12. 12. Reading Speed<br />Reading speed is measured in kB/s<br />Reading speed determines the transfer of data in one second.<br />1× or 1-speed which gives a data transfer rate of 150 kB/s in the most common data format.<br />Maximum speed available today is 52x.<br />12<br />
  13. 13. Writing Data On CD-Rom<br />
  14. 14. Writing Data On CD-ROM<br />A laser is used to heat a chemical dye in the disc to create marks that will be read as data.<br />As marks (pits) are created through burns, this process is also referred as burning.<br />Burning a CD is comparatively slower than reading it.<br />Maximum burning speed is 32x.<br />14<br />
  15. 15. File System<br />The format of the CD (file system) describes how the data is stored on the CD.<br />The earliest file system was High Sierra Standard.<br />The ISO 9660format is now the most common format.<br />15<br />
  16. 16. Tracks and Sectors<br />For burning, the first process is to format a blank CD.<br />CD-ROM drive creates a set of concentric rings, called tracks on each side of CD.<br />Tracks are divided into short segments called sectors.<br />Sectors are where data is stored physically.<br />16<br />Tracks<br />
  17. 17. Writing Methods<br />There are many methods to write a CD.<br />Monosession: Creates a single session on the disc.<br />Multisession: This method lets a CD to be written several times, by creating a 14MB-long table of contents (TOC) de 14Mo for each session. <br />17<br />
  18. 18. Storage Capacity Of CD-Rom<br />
  19. 19. Storage Capacity of CD-ROM<br />Storage capacity is the maximum limit of data storage on a CD.<br />A standard compact disc can store 650 MB of data or about 70 minutes of audio.<br />A new generation of compact disc, however, can hold 700 MB of data or 80 minutes of audio. <br />19<br />
  20. 20. Advantages of CD-ROM<br />Large storage space<br />Compactand light<br />Can be manufactured on a large scale<br />20<br />
  21. 21. Disadvantage Of CD-ROM<br />Slow Writing speed<br />Not easily re-writable<br />Cost Concerns<br />21<br />
  22. 22. Summary<br />Compact Disk is a type of optical storage.<br />It holds data through physical marks.<br />Its is played in a CD-Player, and is read at different speeds.<br />Files system is required to write data on CD by different methods.<br />CDs are compact storage devices that can be moved from on place to another easily.<br />There is always a doubt in their durability.<br />22<br />
  23. 23. References<br /><br /><br /><br /><br /><br /><br />23<br />
  24. 24. Thank You<br />