Chapter 7 Storage Storage What is storage Holds

Chapter 7 Storage

Storage What is storage? Holds data, instructions, and information for future use Ø Storage medium is physical material used for storage Ø § Also called secondary storage p. 354 Fig. 7 -1 Next

Storage What is capacity? Ø Number of bytes (characters) a storage medium can hold Kilobyte (KB) 1 thousand Megabyte (MB) 1 million p. 356 Gigabyte (GB) 1 billion Terabyte (TB) 1 trillion Petabyte (PB) 1 quadrillion Exabyte (EB) 1 quintillion Zettabyte (ZB) 1 sextillion Yottabyte (YB) 1 septillion Next

Storage How does volatility compare? Nonvolatile Volatile Ø Storage medium is nonvolatile—contents retained when power is off Ø Memory is volatile—holds data and instructions temporarily p. 356 ON OFF Screen Display appears Display disappears Memory (most RAM) (chips on motherboard) Data and instructions available to user Data and instructions erased Storage Medium (floppy disks, Zip disks, hard disks, CDs) Contents available to user Contents retained Next

Storage What is a storage device? Reading Process of transferring items from storage media to memory Hardware that records and retrieves items to and from storage media Functions as source of input p. 356 Writing Process of transferring items from memory to storage media Creates output Next

Storage What is access time? Ø Ø Time it takes storage device to locate item on storage medium Time required to deliver item from memory to processor faster transfer rates Transfer rates Stores … Primary Storage Memory (most RAM) Items waiting to be interpreted and executed by the processor Secondary Storage Hard Disk Flash Memory Cards and USB Flash Drives CDs and DVDs slower transfer rates p. 357 Fig. 7 -4 Tape Floppy Disk Operating system, application software, user data and information Digital pictures or files to be transported Software, backups, movies, music Backups Small files to be transported Next

Magnetic Disks What are tracks and sectors? Track is narrow recording band that forms full circle on disk Sector stores up to 512 bytes of data Formatting prepares disk for use and marks bad sectors as unusable p. 357 Fig. 7 -5 Next

Magnetic Disks What is a hard disk? Ø Ø Ø hard disk installed in system unit High-capacity storage Consists of several inflexible, circular platters that store items electronically Components enclosed in airtight, sealed case for protection Longitudinal recording Perpendicular recording p. 358 Fig. 7 -6 Next

Magnetic Disks What are characteristics of a hard disk? Sample Hard Disk Characteristics Advertised capacity Platters Read/write heads Cylinders Bytes per second Sectors per track Sectors per drive Revolutions per minute Transfer rate Access time p. 359 Fig. 7 -7 120 GB 3 6 16, 383 512 63 234, 441, 648 7, 200 133 MB per second 8. 9 ms actual disk capacity Next

Magnetic Disks How does a hard disk work? Step 3. Step 2. When software requests a disk access, read/write heads determine current or new location of data. Small motor spins platters while computer is running. Step 4. Step 1. Circuit board controls movement of head actuator and a small motor. p. 360 Fig. 7 -8 Head actuator positions read/write head arms over correct location on platters to read or write data. Next

Magnetic Disks platter What is a cylinder? Ø Vertical section of track through all platters Ø Single movement of read/write head arms accesses all platters in cylinder track sector read/write head platter sides p. 360 Fig. 7 -9 cylinder Next

Magnetic Disks What is a head crash? Ø Ø Occurs when read/write head touches platter surface Spinning creates cushion of air that floats read/write head above platter § § Clearance between head and platter is approximately two-millionths of an inch A smoke particle, dust particle, or human hair could render drive unusable hair read/write head dust smoke clearance p. 360 -361 Fig. 7 -10 platter Next

Magnetic Disks What is a disk cache? Ø Portion of memory that processor uses to store frequently accessed items processor disk cache first request for data—to disk cache second request for data—to hard disk p. 361 Fig. 7 -11 Next

Magnetic Disks What is a miniature hard disk? Ø Ø Ø Provide users with greater storage capacities than flash memory Some have a form factor of less than 1 inch Storage capacities range from 2 GB to 100 GB p. 362 Fig. 7 -12 Next

Magnetic Disks What are external hard disks and removable hard disks? Ø Used to back up or transfer files Removable hard disk—hard disk that you insert and remove from hard disk drive External hard disk—freestanding hard disk that connects to system unit p. 362 Fig. 7 -12 Next

Magnetic Disks What is a disk controller? Chip and circuits that control transfer of items from disk SATA (Serial Advanced Technology Attachment) controller uses serial signals to transfer data, instructions, and information SCSI EIDE (Enhanced Integrated Drive (Small Computer System Interface) Electronics) controller supports four controller supports up to fifteen devices including hard disks, CD hard disks, provides connections for and DVD drives, tape drives, printers, CD and DVD drives scanners, network cards p. 363 Next

Magnetic Disks What is online storage? Ø Ø Service on Web that provides storage for minimal monthly fee Files can be accessed from any computer with Web access Large files can be downloaded instantaneously Others can be authorized to access your data p. 363 Fig. 7 -14 Next

Magnetic Disks What is a floppy disk? Ø shutter Portable, inexpensive storage medium (also called diskette) shell liner Thin, circular, flexible film enclosed in 3. 5” wide plastic shell magnetic coating metal hub flexible thin film p. 364 Next

Magnetic Disks What is a floppy disk drive? Ø Device that reads from and writes to floppy disk § Ø One floppy drive, named drive A Also called secondary storage External floppy disk drive attaches to a computer with a cable Floppy disk drive built into a desktop computer p. 364 Fig. 7 -15 Next

Magnetic Disks What is a write-protect notch? Ø Ø Small opening with a cover that you slide Protects floppy disk from being erased accidentally write-protected notch open means you cannot write on the disk notch closed means you can write on the disk p. 365 not write-protected hole on this side means disk is high density Next

Magnetic Disks How do you compute a disk’s storage capacity? Ø Multiply number of sides, number of tracks, number of sectors per track, and number of bytes per sector § For high-density disk: 2 sides 80 tracks 18 sectors per track 512 bytes per sector = 1, 474, 560 bytes Capacity: Characteristics of a 3. 5 -inch High-Density Floppy Disk p. 359 1. 44 MB Sides: 2 Tracks: 80 Sectors per track: 18 Bytes per sector: 512 Sectors per disk: 2880 Next

Magnetic Disks What is a Zip disk? Ø Ø Magnetic medium that stores 100 MB to 750 MB of data Used to back up and to transfer files § Backup is duplicate of file, program, or disk in case original is lost c Ø Zip disks require a Zip drive — high capacity drive that reads from and writes on a Zip disk p. 365 Fig. 7 -16 c c Next

Optical Discs What are optical discs? Ø Ø Ø Flat, round, portable metal discs made of metal, plastic, and lacquer Can be read only or read/write Most PCs include an optical disc drive p. 366 Fig. 7 -17 Push the button to slide out the tray. Insert the disc, label side up. Push the same button to close the tray. Next

Optical Discs How does a laser read data on an optical disc? disc label lens pit 0 prism Step 1. Laser diode shines a light beam toward disc. p. 367 Fig. 7 -18 laser diode lightsensing diode lens land Step 2. If light strikes a pit, it scatters. If light strikes a land, it is reflected back toward diode. 1 prism laser diode lightsensing diode Step 3. Reflected light is deflected to a light-sensing diode, which sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0. Next

Optical Discs How is data stored on an optical disc? Ø Ø Typically stored in single track Track divided into evenly sized sectors that store items single track spirals to edge of disc sectors p. 367 Fig. 7 -19 Next

Optical Discs How should you care for an optical disc? Do not eat, smoke, or drink near a disc Do not expose the disc to excessive heat or sunlight Do not stack discs Do not touch the underside of the disc Do store the disc in a jewel box when not in use p. 230 Fig. 7 -20 Do hold a disc by its edges Next

Optical Discs What is a CD-ROM? Ø Ø Compact disc read-only memory Cannot erase or modify contents Typically holds 650 MB to 1 GB Commonly used to distribute multimedia and complex software p. 369 Fig. 7 -22 Next

Optical Discs What is the data transfer rate of a CD-ROM drive? Ranges from 48 X to 75 X or faster 75 X is 150 KBps (KB per second) 75 X 75 150 KBps = 11, 250 KBps or 12. 25 MBps 48 X: 48 150 KBps = 7, 200 KBps or 7. 2 MBps p. 369 Next

Optical Discs What is a Picture CD? Stores digital versions of roll of film Film developers offer Picture CD service Can be modified using photo editing software Step 1. Drop off film to be developed. Mark the Picture CD box on the film-processing envelope. p. 370 Fig. 7 -23 Step 3. Step 2. When you pick up prints and negatives, a Picture CD contains digital images of each photograph. At home, print images from Picture CD on your ink-jet photo printer. At a store, print images to Picture CD at kiosk. Next

Optical Discs What are CD-Rs and CD-RWs? Must have CD recorder or CD-R drive CD-R (compact disc-recordable) — disc you can write on once c Cannot erase disc’s contents CD-RW (compact disc-rewritable) — erasable disc you can write on multiple times ce Must have CD-RW software and CD-RW drive p. 371 Next

Optical Discs What is a DVD-ROM (digital versatile disc-ROM or digital video disc-ROM)? Ø Ø Ø Must have DVD-ROM drive or DVD player to read DVD-ROM Stores databases, music, complex software, and movies Blu-ray discs have storage capacity of up to 27 GB HD-DVD discs have storage capacity of up to 45 GB UMD can store up to 1. 8 GB p. 372 Fig. 7 -24 Next

Optical Discs How does a DVD-ROM store data? Ø Ø Ø Two layers of pits are used, lower layer is semitransparent so laser can read through Some are double-sided Many types of recordable and rewritable DVDs are available Ø DVD-R and DVD+R Ø DVD-RW and DVD+RW p. 372 Fig. 7 -25 Next

Tape What is tape? Ø Ø Magnetically coated plastic ribbon capable of storing large amounts of data at low cost Primarily used for backup p. 374 Fig. 7 -27 Next

Tape How is data stored on a tape? Ø Sequential access § § p. 374 Reads and writes data consecutively, like music tape Unlike direct access — used on floppy disks, Zip disks, hard disks, CDs, and DVDs — which can locate particular item immediately Next

PC Cards What is a PC Card? Ø Ø Adds capabilities to computer Credit-card-sized device commonly used in notebook computers p. 374 Figs. 7 -28– 7 -29 Next

Miniature Mobile Storage Media What is miniature mobile storage media? Ø Storage for small mobile devices p. 375 Fig. 7 -30 Next

Miniature Mobile Storage Media What are common types of flash memory cards? Compact. Flash Smart Media Memory Stick p. 376 Fig. 7 -31 Secure Digital x. D Picture Card Next

Miniature Mobile Storage Media How does one type of flash memory card work? p. 377 Fig. 7 -32 Next

Miniature Mobile Storage Media What is a USB Flash Drive? Ø Ø Ø Plugs in a USB port on a computer or mobile device Storage capacities up to 4 GB May eventually make the floppy disk obsolete p. 377 Fig. 7 -33 Next

Miniature Mobile Storage Media What is a smart card? Ø Ø Stores data on microprocessor embedded in small card Input, process, output, and storage capabilities p. 378 Fig. 7 -34 Next

Microfilm and Microfiche What are microfilm and microfiche? Store microscopic images of documents on roll or sheet of film Images recorded using computer output microfilm recorder Microfilm — 100 - to 215 -foot roll of film p. 379 Fig. 7 -35 Microfiche — small sheet of film, usually 4” 6” Next

Microfilm and Microfiche How do life expectancies of various media compare? Ø Microfilm and microfiche have longest life of any storage media p. 379 Fig. 7 -36 Next