Presentation 14 che-section-b

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  1. 1. Computer & Computation Muhammad Muneeb 3/17/2015 1
  2. 2. DATA: Unorganized collection of facts which is able to be organized into useful information. Storage: Storage holds data, instructions, and information for future use. For example, computers can store hundreds or millions of customer names and addresses. Storage holds these items permanently. Storage devices: Hardware components that read data from and write data to storage media called storage devices. 3/17/2015 3
  3. 3. There are three types of storage devices. 1) Magnetic Storage Devices 2) Optical Storage Devices 3) Solid-State Storage Devices: 3/17/2015 4
  4. 4. Such devices, coated with magnetically sensitive material (i.e. Iron Oxide that react to a magnetic material) Uses magnet to access data Use binary relation to store data (1 and 0 form) The storage capacity is unlimited. Magnetic disk are less vulnerable to data corruption due to careless handling. E.g. (Floppy Disk, Hard Disk) 3/17/2015 5
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  6. 6. Use laser to read data and write data to the reflective surface of optical disc They are better storage medium than magnetic storage devices. Optical disc storage system consists of a metallic or plastic disk. Due to there compact size and light weight, optical disks are easy to handle store and port from one place to another. E.g. (CD, DVD, And Blue Ray Disc) 3/17/2015 7
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  8. 8. Non volatile Less Expensive from blue rays High Speed They stored data on memory circuits rather than disk or tapes. They store data electronically not in a magnetic or optical form. They dont need to move a head or sensor to find data. E.g. ( Flash drive, Memory Cards) 3/17/2015 9
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  10. 10. Hard Disk Drive (HDD) 3/17/2015 11
  11. 11. Introduced by IBM in 1956 became the dominant secondary storage device for general purpose computers by the early 1960s Data storage device for storing and retrieving digital information using platters (rapidly rotating disks). Non volatile. Individual blocks of data can be stored or retrieved in any order rather than sequentially. It consist one or more rigid platters. 3/17/2015 12
  12. 12. There are just a large shiny circular plates of magnetic material called platter, divided into billions of areas. Each one of these areas can be independently magnetized to store disk drive (HDD) records the data by magnetizing ferromagnetic material directionally to represent either 0 or 1 binary digit. They read the data back by magnetization of the material. 3/17/2015 13
  13. 13. There are two ways to measure the performance of a hard disk. 1) Data rate: It is the number of bytes per seconds that the drive can delivers to the CPU the rate between 5 and 40 megabytes are common. 3/17/2015 14
  14. 14. 2) Seek Time: The seek time is the amount of time between when the CPU request the file and when the first byte of the file is sent to the CPU. Times Between 10 and 20 milliseconds are common. 3/17/2015 15
  15. 15. More than 200 companies have manufactured HDDs over time. Most popular production companies today: Western Digital, Seagate, and Toshiba. Worldwide revenues for disk storage were $32 billion in 2013, down about 3% from 2012.. The estimated 2013 market shares are about 4045% each for Seagate and Western Digital and 1316% for Toshiba. 3/17/2015 16
  16. 16. There are types of hard drive. 1) ZIP/ Bernoulli disk. 2) Disk pack. 3) Winchester Disk. 3/17/2015 17
  17. 17. Consist of single hard disk platter. Storage capacity 8GB to 500GB or more May be portable or fixed. The fixed type is connected permanently. Portable type is connected to computer during use and then after use it can be disconnected. It can be loaded/Unloaded into a Zip drive as we insert/remove a video cassette into video cassette player. 3/17/2015 18
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  19. 19. Consists of multiple hard disk platter. All disk revolved together around single central shaft. When not in use user can store a disk pack off- line in a plastic case. This gives virtually unlimited storage capacity to disk pack. Storage capacity of disk pack varies from hundred GB to several Thousand GB. Diameter 14-inch introduced by IBM. 3/17/2015 20
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  21. 21. Consists of multiple Hard disk platters Mounted on a single central shaft. Its hard disk platters and disk drive are sealed together and can not be separated from each other. Have large storage capacity because all surfaces of all disk platters are used for data recording. Storage capacity varies from few gigabits to few terabits. 3/17/2015 22
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