22 storage devices
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Storage holds data and information for future use. Common storage mediums include hard disks, CDs, DVDs, memory cards, and USB flash drives. Storage devices, like hard disks, record and retrieve data from these storage mediums. Hard disks use magnetic disks to store data in tracks and sectors. They have faster access times than optical discs but slower times than memory. Other storage media include floppy disks, optical discs like CDs and DVDs, and flash memory cards.
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22 storage devices
- 2. What is Storage Storage holds data, instructions and information for future use. All the programs when started are loaded from a storage device onto computer memory Users store a variety of data on mainframes, servers, desktops, notebooks, handheld devices, smart phones etc
- 3. Storage Medium A storage medium is the physical material on which a computer keeps data, instructions and information. Hard disks, CDs, DVDs, memory cards, USB flash drives etc are all storage mediums or secondary storage devices Storage capacity is the number of bytes a storage medium can hold
- 4. Storage terms 1 KB = 2 10 Bytes = 1,024 bytes 1 MB = 2 20 Bytes = 1,048,576 bytes 1 GB = 2 30 Bytes = 1,073,741,824 bytes 1 TB = 2 40 Bytes = 1,099,511,627,776 bytes A storage medium is non-volatile, that is, items on storage medium remain intact even when power is removed
- 5. Storage device A storage device is the computer hardware that records and/or retrieves items to and from the storage media. Writing is the process of transferring data, instructions and information from memory to storage medium. Reading is the process of transferring these items from a storage medium into memory.
- 6. When storage devices write data onto storage medium, they are generating computer output When storage devices read from storage media, they are generating input for the computer. * however, storage devices are not categorised into input or output devices
- 7. Speed The speed of storage devices and memory is defined by access time. The time required to locate an item on a storage medium The time required to deliver an item from memory to the processor Access time of storage devices is slow as compared to memory devices
- 8. Memory Most RAM Storage Hard Disk Flash Memory cards and USB drives CDs, DVDs etc
- 9. Magnetic Disks Magnetic disks use magnetic particles to store items on a disks surface Each particle on the magnetic disk represents a bit Formatting is process of dividing the disk into tracks, sectors and clusters (allocation unit)
- 11. Hard Disk A hard disk is a storage device that contains one or more inflexible magnetic disks
- 12. The magnetic disks in a hard disk rotate at a speed from 5,000 to 15,000 rpm The data transfer rate of hard disks range from 15 mbps to 320 mbps Hard disks improve their access time by using disk caching Disk cache is a memory chip on hard disk that stores frequently accessed items
- 13. A group of two or more integrated hard disks is called RAID (Redundant Array of Independent Disks) Miniature hard disks are present in digital cameras, portable media players, smart phones etc A pocket hard drive or portable hard drive also has a miniature hard disk External or removable hard disks
- 14. Hard Disk Controller A disk controller consists of a special- purpose chip and electronic circuits that control the transfer of data. An interface is required by the hard disk controller to transfer data to and from the hard disk SATA (Serial Advanced Technology Attachment) EIDE (Enhanced Integrated Drive Electronics) SCSI Interfaces SAS (Serial Attached SCSI)
- 15. Online storage Online storage is a service provided on the web that gives hard disk storage to users for free or for a nominal monthly fee To access data from other computers To store files like audio, video and graphics on the internet instead of downloading onto local hard disk To allow others to access your files To store backups
- 16. Other storage media Floppy disks : A flexible plastic film with a magnetic coating Optical discs: A storage media that consists of portable disc made of metal, plastic and lacquer that is written and read by a laser Read/write feature Double-sided discs
- 17. Disc type Features CD-ROM Read only CD-R Read and write CD-RW Read, write and erase DVD-ROM, BD-ROM, HD DVD- ROM Read only DVD-R, BD-R, HD DVD-R Read and write DVD-RW, DVD-RAM, BD-RE, HD DVD-RW Read, write and erase
- 18. PC cards and Express cards (developed by Personal Computer Memory Card International Association) Flash memory cards (solid state media) Secure Digital (SD) Mini SD USB flash drives Smart card (sim, visa card, master card etc) Enterprise storage