CHAPTER 4 DATA STORAGE

CHAPTER 4 DATA STORAGE

1. - Holds data, instructions, and information for future use

   • - Storage medium is physical material used for storage

2. Volatility Compare

   • Capacity - Number of bytes a storage medium can hold
   • Storage medium is nonvolatile - contents retained when power off
     • Memory is volatile - holds data and instructions temporarily

3. Storage Device

   • Reading (input) - process of transferring items from storage media to memory
     • Writing (output) - from memory to storage media
       • Online storage - service on Web provides storage monthly fee

4. Access Time

   • - Time it takes storage device to locate item on storage medium
     • - Time required to deliver item from memory to processor

5. Magnetic Disks

   • Tracks - narrow recording band that forms full circle on disk
     • Sector - stores up to 512 bytes of data

6. Hard Disk (High-capacity storage)

   • - Consists of several inflexible, circular platters that store items electronically
     • - Components enclosed in airtight, sealed casse for protection
       • LONGITUDINAL RECORDING
       • PERPENDICULAR RECORDING
       • EXTERNAL HARD DISK: freestanding hard disk that connects to system unit
         • REMOVABLE HARD DISK: insert and remove from hard disk drive

7. Head Crash

   • - Occurs when read/write head touches platter surface
     • - Spinning creates cushion of air that floats read/write head above platter

8. RAID (Redundant Array of Independent Disks)

   • - Connects multiple smaller disks into a single unit

9. Disk Controller

   • - Chip and circuits that control transfer of items from disk
     • SATA (Serial Advanced Tech Attachment)
       • controller uses serial signals to transfer data
     • SCSI
       • supports up to 15 devices
     • EIDE (Enhanced Integrated Drive Electronics)
       • supports 4 hard disks provides connections
     • SAS
       • supports many connected devices at once

10. CD-ROM (Compact Disc Read-Only Memory)

    • - cannot erase/ modify contents
      • - commonly used to distribute multimedia and software
        • CD-R (compact disc-recordable)
          • disc u can write on once
        • CD-RW(compact disc-rewritable)
          • erasable disc

11. USB Flash Drive

    • - Plugs in a USB port on computer/ mobile device
      • - Storage capacities up to 64 GB
        • - May eventually make the floppy disk nearly obsolete

12. Smart Card

    • - Stores data on microprocessor embedded in small card
      • - Input, process, output, and storage capabilities
        • MICROFILM: store images on sheet of film
        • MICROFICHE: images recorded using computer output

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