1 Computer Hardware Unit B

2 Objectives Introduce Storage Technology Compare Storage Technologies Compare Storage Media and Devices Explore Floppy Disk Technology Explore Hard Disk Technology Explore CD/DVD Technology

3 Objectives Explore Solid State Storage Examine Input Devices Compare Display Devices Compare Printers Understand Expansion Slots, Cards, and Ports Explore Peripheral Devices

4 Storage Technology Storage Medium: holds data –Disk, CD, DVD Storage Device: mechanical apparatus that records and retrieves data from medium –Disk drives, CD drives Storage = Medium + Device

5 Storage Process Data copied from storage device to RAM Processed in RAM –Volatile (temporary) high speed storage –RAM is connection between the storage device and media Data copied back to storage medium (permanent) Storing data is writing/saving file Retrieving data is reading/loading/opening file

6 Storage Process A computer works with data that has been coded to be represented by 1s and 0s (binary system) When data is stored, 1s and 0s converted into signals The transformation of 1s and 0s depends on the storage technology Data representation makes it possible to convert letters, sounds, and images into electronic symbols

7 Storage Comparison Three main types of storage technologies for PCs: Magnetic –Hard disk, floppy disk, zip disk and tape Optical –CD and DVD Solid stage –Cards, pens, and sticks

8 Magnetic Storage Magnetizes microscopic particles on medium surface Permanent, but modifiable Read-write head Not very durable

9 Floppy Disks and Drives Floppy disk characteristics –Typically 3½ inches in diameter. –Typically hold 1.44 megabytes. –Inserted into floppy disk drive to be read from or written to.

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11 Floppy Disks and Drives, Cont’d. Disk is divided into tracks, sectors, and clusters. The disk’s file directory keeps track of the contents of the disk so files can be retrieved (by filename) at a later time.

12 Floppy Disks and Drives, Cont’d. Using floppy disks –Must be inserted into the proper drive in the proper direction. –Should not be removed when the disk is being accessed. High-capacity removable magnetic disks and drives –Zip disks (750 MB) –SuperDisks (240 MB)

13 Hard Disk Drives Hard drive characteristics –Metal disk onto which data is stored magnetically. –Disks are usually permanently sealed inside the hard drive—allows faster speeds and storage of more data than removable systems. –Can be internal or external.

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15 Hard Disk Drives, Cont’d. Hard drive characteristics, cont’d –Organized into tracks, sections, clusters, and cylinders (the collection of tracks located in the same location on a set of hard disk surfaces). –Read/write head doesn’t touch the surface of the disk. –Bumping PC when disk is being accessed or dust or other obstacles on a hard-disk system can cause a head crash and damage the surface of the disk.

16 Hard Disk Drives, Cont’d. Disk access time. –Factors: seek time, rotational delay, data movement time Can use multiple partitions. Disk cache—strategy for speeding up system performance. Hard drive standards (EIDE, SCSI, Fibre Channel, USB).

17 Hard Disk Drives, Cont’d. Portable hard drive systems Offer large storage capacities and portability. –Either entire drive or just hard disk cartridge is transported.

18 Hard Disk Drives, Cont’d. Storage systems for large computer systems and networks –Storage servers containing racks of hard drives. –Network attached storage (NAS). –Storage area networks (SANs). –RAID (for increased performance and/or fault tolerance).

19 Optical Disc Systems Laser beams write and read data packed at very tight storage densities, many times finer than that of a typical magnetic disk. Are typically 4½-inch discs, but can be a variety of shapes and sizes. Data is stored optically on a continuous spiral track. Can be CDs or DVDs.

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21 Read-Only Discs: CD-ROM and DVD-ROM Discs CD-ROM discs cannot be written to or erased and typically hold 650 MB (e.g. music CDs). DVD-ROM discs are similar to CD-ROM discs, but have higher capacity of 4.7 GB to 17 GB (e.g. movie DVDs). Data is stored by burning pits into the disc surface that can be read using a laser beam.

22 Optical Storage Stores data as microscopic light and dark spots on disk surface Pits and lands Uses laser lights More durable

23 Solid Stage Storage Stores data in a non-volatile, erasable, low- power chip Data is organized in a microscopic grid of cells A card reader transfers data between the card and computer Durable through temperature changes, vibrations, and magnetic fields Good for digital cameras and MP3 players Very high cost

24 Comparing Storage Devices VersatilityDurabilitySpeed –Access time –Milliseconds –Random vs. sequential access –Data transfer rate Capacity –KB, MB, GB, TB –Disk density

25 Comparing Storage Devices Device Capacity Comments Floppy disk 1.44 MB Cannot hold large files SuperDisk 120 or 240 MB Full-system backup requires multiple disks Zip disk 100, 250, 750 MB Full-system backup requires multiple disks Fixed disk 80 GB (avg) Fast, convenient, economical, high storage. Susceptible to damage or theft External hard drive 80 GB (avg) Drive can be removed and locked in a secure location CD-R 700 MB Limited capacity & shelf-life, cannot be reused CD-RW 700 MB Limited capacity, reusable Writable DVD 4.7 GB Standards still in development Tape 30 GB (avg) Good capacity, but slow

26 Adding Storage Devices Upgrading System Unit contains drive bays –5 ¼” or 3 ½” –Access from either outside or inside

27 Floppy Disks Advantages: –Portable, inexpensive, removable Disadvantages: –Low storage capacity of 3 ½” disks –Slower than hard disk drive High Density (HD or HDD) –HD DS means “high density, double- sided”

28 Floppy Disks 3½” disk: 1.44 MB Zip disks (Iomega): 100, 250 and 750 MB SuperDisks (Imation): 120 or 240 MB

29 Hard Disks (Fixed Disks) One or more platters with read/write heads Capacity averages 80 GB Very fast access times (rpm) Platters divided into tracks, sectors, cylinder Controller (circuit board) –Ultra ATA, EIDE, SCSI DMA transfers data directly from drive to RAM Head Crash

30 Tape Storage Sequential storage stores data in long sequence of bits –Stretches from one end of tape to another –Makes it slower to access than hard drive –Hundreds or thousands of feet of tape Tape cartridge is removable Internal or external models

31 CD Technology CD-ROM: Compact Disk Read-Only Memory –Manufactured; cannot change; 680 MB CD-R: Compact Disk Recordable –You record; cannot be erased or modified CD-RW: Compact Disk Rewritable –You record; can erase and modify Archiving Data

32 DVD Technology Digital Video Disk Originally alternative to VCR 4.7 GB Manufactured Can play CD-ROM and most CD- Rs and CD-RWs

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35 Solid State Storage Circuitry arranged in a grid –Each grid cell has 2 transistors (gates) –Open gates are 1s; Closed gates are 0s Data is non-volatile –Chip retains data without power Some devices require a card reader Examples: –USB flash drive, CompactFlash cards, MultiMedia cards, Secure Digital cards, and SmartMedia cards

36 Solid State Storage Why use solid stage storage? –Data can be easily transferred between devices such as digital camera to computer, OR computer to MP3 player –Cards can be reused –Can transfer data between computers

37 Other Types of Storage Systems, Cont’d Smart card: credit-card-sized piece of plastic that contains some type of computer circuitry. Holds less than a few megabytes. –Commonly used to store prepaid amounts of digital cash or personal information. Smart card readers are attached to a PC or built into a cell phone, keyboard, or other device.

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39 Input Devices Keyboards –Most computers have one –Typing keypad, navigation keypad, Function keys, Modifier keys Pointing Devices –Manipulate on-screen pointer and graphical controls –Mouse, pointing stick, TrackPoint, trackpad, trackball, joy stick Also: scanners, digital cameras, graphics tablets, microphones, electronic instruments

40 Display Devices Graphics card –Video memory, AGP expansion card –Accelerator technology CRT: Cathode Ray Tube –Inexpensive and dependable LCD: Liquid Crystal Display –Expensive; found on notebooks –Limited viewing angles –Active Matrix or TFT (thin film transistor) Plasma –Illuminates miniature fluorescent lights –Compact, light, expensive

41 Display Device Image Quality Screen size (13” to 21”) –vis (viewable image size) Dot pitch (dp) –Distance between like-colored pixels –.26 or.23 typical (smaller is better) Resolution –Horizontal and vertical pixels on screen –640 x 480, 800 x 600 and 1024 x 768 Color or Bit Depth –Number of colors that can be displayed –24-bit (true color) = millions of colors

42 Printer Comparison Criteria Resolution (dpi) MaterialsCost Qualityvs.Price Speed (ppm or cps) Duty Cycle

43 Printer Types Ink Jet printer Solid Ink printer Thermal Transfer printer Dye Sublimation printer Laser printer Dot Matrix printer

44 Ink Jet Printer Nozzle-like print head sprays ink Low cost Can smudge Color; black and white

45 Solid Ink Printer Crayon-like ink is melted and sprayed Vibrant colors on most types of paper

46 Thermal Transfer Printer Uses wax that is melted Needs special paper/transparencies Expensive

47 Dye Sublimation Printer Like wax transfer, but uses heated dye Need special paper Excellent color quality Expensive

48 Laser Printer Same technology as photocopier Fax High quality Fast

49 Busses Data Bus: circuits on which data travels within the computer –Between RAM and CPU –Between RAM and storage devices Expansion Bus –Part of data bus between RAM and the peripherals

50 Expansion Slots and Cards Cards also called expansion boards, controller cards, adapters Desktops have 4 to 8 slots Standard cards –Graphics or video card –Modem card –Sound card –Network card

51 Expansion Slot Types ISA: Industry Standard Architecture –Older; modems and slow devices PCI: Peripheral Component Interconnect –Fast; graphics, sound, video AGP: Accelerated Graphics Port –Fast; graphics

52 PCMCIA (PC Card) Personal Computer Memory Card International Association Found on notebook computers Type I, II, III

53 Expansion Ports Jacks or connectors Mouse, keyboard, serial, USB Cables

54 USB ports Most popular for connecting peripheral devices Most computers have several Mouse, scanners, joysticks, USB Flash drives Windows automatically recognizes most USB devices

55 Peripherals Equipment attached to computer to increase its functionality Projection devices, scanners, Web cam, joy stick

56 Peripherals Connected through cables to the motherboard through a port –May require expansion card –Use grounding equipment for safety –Device driver software tells computer how to interact with device –PnP (Plug and Play) recognizes device once it is connected

57 Issue Why Recycle Computers?

58 Computer Hardware End