Chapter 7: StorageMemory Versus StorageWhat is storage?- Media and devices used to store and retrieve data, instructions, and informationHow does storage differ from memory?- (Memory is also called primary storage or RAM)- Storage (also called secondary storage):- Stores items for future use, rather than temporarily- Storage is nonvolatile, rather than volatile- When you want to work with a file, you read it from storage and place it in memory- When you are finished with the file, you write it from memory into storageHow does volatility compare?- Screen display and contents of most RAM (memory) erased when power is off- Contents of storage retained when power is offWhat is a storage device and a storage medium?- Storage deviceo Hardware that records and retrieves items to and from a storage medium- Storage mediumo Physical material on which a computer keeps data, instructions, and informationWhat is reading and writing?- Readingo Process of transferring data, instructions, and information from a storage medium into memoryo Serves as a source of input- Writingo Process of transferring items from memory to a storage mediumo Serves as a source of outputWhat is access time?- Amount of time it takes device to locate item on disk- Defines speed of disk storage deviceo Tape (slowest, least expensive)o Floppy Disko Compact DiscPage 1 of 9o Hard DiskWhat is capacity?- Number of bytes (characters) storage medium can holdo Kilobyte KB – 1 thousando Megabyte MD – 1 milliono Gigabyte GB – 1 billiono Terabyte TB – 1 trilliono Petabyte PB – 1 quadrillionFloppy DisksWhat is a floppy disk?- Portable, inexpensive storage medium- Today’s standard disk is 3.5” wide- HD (High Density disk) Stores 1.44MBWhat are the parts of a floppy disk?- Thin, circular, flexible film enclosed between two linersHow are floppy disk drives designated?- One floppy driveo drive A- Two floppy driveso drive Ao drive BHow does a floppy disk drive work?- 1: Shutter moves to expose recording surface on disk- 2: Signal sent to control movement of read/write heads and disk- 3: If write instruction, circuit board verifies whether disk can be written to- 4: Motor causes floppy disk to spin- 5: Motor positions read/write heads over correct location on disk- 6: Read/write heads read data from or write data on the floppy diskWhat are tracks and sectors?- Track is narrow recording band that forms full circle on disk surface- Sector can store up to 512 bytes of datao 80 tracks per side X 18 sectors per track X 2 sides per disk X 512 bytes per sector = 1,474,560 bytes = 1.44 MBWhat is formatting?Page 2 of 9- Process of preparing disk for reading and writing- Formatting marks bad sectors as unusableHow do you care for a floppy?- Proper care helps maximize disk’s life - Floppy disk can last at least seven yearso Never open the shutter and touch the disk’s recording surfaceo Avoid exposure to heat and coldo Avoid exposure to magnetic fieldso Avoid exposure to contaminants such as dust, smoke, or salt airo Keep disks in a storage tray when not using themWhat is a write-protect notch?- Small opening with a cover that you slide- Protects floppy disks from being erased accidentallyo notch open means you cannot write on the disko notch closed means you can write on the diskHigh-Capacity DisksWhat is a high-capacity disk drive?- Uses disks with capacities of 100 MB and greater- Primarily used to backup files and transfer fileso Zip® driveo Uses a Zip® disk that can store 100 MB or 250 MB of dataWhat is a backup?- Duplicate of file, program, or disk that you can use if original is lost, damaged, or destroyedHard DisksWhat is a hard disk?- High-capacity storage (20 – 100 GB)- Consists of several inflexible, circular platters that store items electronically- Components enclosed in airtight, sealed case for protectionHow does a hard disk work?- 1: Circuit board controls movement of head activator and small motor- 2: Small motor spins platters- 3: When software requests disk access, read/write heads determine location of data- 4: Head actuator positions read/write head arms over correct location on platters to read or write dataPage 3 of 9What is a cylinder?- Location of a single track through all platters- Single movement of read/write head arms can read same track on all plattersWhat is a head crash?- Occurs when read/write head touches platter surface- Spinning creates cushion of air that floats read/write head above plattero clearance between head and platter is approximately two millionths of an incho gap is half the diameter of a dust particleWhat is a disk cache?- Portion of memory processor uses to store frequently accessed itemsWhat is a partition?- Formatted hard disk divided into separate areas called partitions- Each partition functions as if it were a separate hard disk drive- Designation for first partition or for a single partition on hard disko drive C- Designation for second partition on hard disko drive DWhat is a removable hard disk?- Disk drive in which a plastic or metal case surrounds the hard disk so you can remove it from the drive- Used for backup or to transfer filesHow does RAID work?- Disk system that duplicates data, instructions, and information to improve data reliability ensuring that data is not lost if one drive failso Mirroring has one backup disk for each disko Striping stores data across multiple disksWhat Windows utilities maintain a hard disk drive?- Backup- Disk Cleanup- Disk Defragmenter- Scheduled TasksWhat is an Internet hard drive?- Service on Web that provides storage to computer userso Most offer free storagePage 4 of 9o Revenues come from advertisersWhat are advantages of an Internet hard drive?- Large audio, video, and graphics files can be downloaded to an Internet hard drive instantaneously- Files can be accessed from any computer or device with Web access- Others can be authorized to access data from your Internet hard drive- Allows offsite backups of dataCompact DiscsWhat is a compact disc (CD)?- Storage medium - Most PCs include some type of compact disc drive- Available in variety of formatso CD-ROMo CD-Ro CD-RWo DVD-ROM- DVD+RWHow do you use a compact disc?- CD drives can read compact discs, including audio discsHow does a laser read data on a compact disc?- 1: Laser diode shines light beam toward compact disc- 2: If light strikes pit, it scatters. If light strikes land, it is reflected back toward laser diode.- 3: