Computer Peripherals

Computer Peripherals

Peripherals Devices that are separate from the basic computer Not the CPU, memory, power supply Classified as input, output, and storage Connect via Ports parallel, USB, serial Interface to systems bus SCSI, IDE, PCMCIA Approach, 3rd ed., 2003 2

Storage Devices Primary memory Expanded storage Secondary storage Data and programs must be copied to primary memory for CPU access Permanence of data Direct access storage devices (DASDs) Online storage Offline storage loaded when needed Approach, 3rd ed., 2003 3

Speed Measured by access time and data transfer rate Access time: average time it takes a computer to locate data and read it millisecond = one-thousandth of a second Data transfer rate: amount of data that moves per second Approach, 3rd ed., 2003 4

Hierarchy of Storage Device CPU Registers Cache Memory (SRAM) Conventional Memory (DRAM) Expanded Storage (RAM) Typical Access Times 15 to 30 nanoseconds 50 to 100 nanoseconds 75 to 500 nanoseconds Throughput Rate Hard Disk Drive 10 to 50 milliseconds 600 to 6,000 KB/sec Floppy Disk 95 milliseconds 100 to 200 KB/sec CD-ROM 100 to 600 milliseconds 500 to 4,000 KB/sec Tape.5 and up seconds 2,000 KB/sec (cartridge) Approach, 3rd ed., 2003 5

Secondary Storage Devices Hard drives, floppy drives CD-ROM and DVD-ROM drives CD-R, CD-RW, DVD-RAM, DVD-RW Tape drives Network drives Approach, 3rd ed., 2003 6

Magnetic Disks Consist of one or more flat, circular platters made of glass, metal or plastic and coated with a magnetic substance. Approach, 3rd ed., 2003 7

Magnetic Disks (cont.) Track circle Cylinder same track on all platters Block small arc of a track Sector pie-shaped part of a platter Head reads data off the disk Approach, 3rd ed., 2003 8

Magnetic Disks (cont.) Head crash Number of bits on each track is the same! Denser towards the center. CAV constant angular velocity Spins the same speed for every track Hard drives 3600 rpm 7200 rpm Floppy drives 360 rpm Approach, 3rd ed., 2003 9

A Hard Disk Layout Approach, 3rd ed., 2003 10

Cutaway of a floppy disk Approach, 3rd ed., 2003 11

Locating a Block of Data Average seek time: time required to move from one track to another Latency: time required for disk to rotate to beginning of correct sector Transfer time: time required to transfer a block of data to the disk controller buffer Approach, 3rd ed., 2003 12

Magnetic Disks Data Block Format Interblock gap Header Data Formatting disk Disk Interleaving Disk Arrays RAID mirrored, striped Disk Interleaving Approach, 3rd ed., 2003 13

RAID (striping) Approach, 3rd ed., 2003 14

RAID (mirroring) Approach, 3rd ed., 2003 15

Magnetic Tape Offline storage Archival purposes Disaster recovery Approach, 3rd ed., 2003 16

QIC Can hold 120 MB to 25 GB of uncompressed data. Approach, 3rd ed., 2003 17

DAT Data on DAT cartridges are very tightly packed, using a read/write head that rotates at a high speed to pack the tape much more tightly with data. Very tiny but have capacities of 2GB and up. Approach, 3rd ed., 2003 18

Optical Storage A direct access disk written and read by light. CD, CD-ROM, DVD-ROM and DVD- Video are read-only optical disks that are recorded at the time of manufacture and cannot be erased. Approach, 3rd ed., 2003 19

Types of Optical Storage CD-ROM DVD-ROM WORM Magneto optical disks Approach, 3rd ed., 2003 20

CD-ROM Read-only removable medium with large data storage capacity. Data storage is similar to magnetic disk. Laser beam is reflected off the pitted surface of the disk as a motor rotates the disk. Approach, 3rd ed., 2003 21

Layout: CD-ROM vs. Standard Disk CD-ROM Hard Disk Approach, 3rd ed., 2003 22

DVD-ROM Similar to the CD-ROM technology. Uses laser with a shorter light wavelength to allow tighter packing of the disk. Total capacity: 17GB Approach, 3rd ed., 2003 23

WORM Disks Write-once-read-many times Similar to the CD-ROM technology Medium can be altered by using a mediumpowered laser to blister the surface Data stored in concentric tracks, sectored like a magnetic disk Approach, 3rd ed., 2003 24

Magneto-Optical Disks Combine optical and magnetic disk technology. Share advantages of optical disk: capacity, reasonable cost & removability together with the read/write capability of magnetic disks. Approach, 3rd ed., 2003 25

Magneto-Optical Disks (cont.) May be stored near magnets. Limitation: have a much longer seek time & a slower transfer rate than magnetic disks. Approach, 3rd ed., 2003 26

Magneto-Optical Disks (cont.) Approach, 3rd ed., 2003 27

Displays Images made up of thousands of individual pixels or picture element Pixel: The smallest addressable unit on a display screen or bitmapped image. Screens are rated by their number of horizontal and vertical pixels 1024x768 means 1024 pixels are displayed in each row, and there are 768 rows (lines). Approach, 3rd ed., 2003 28

Simplest Pixel Representation Approach, 3rd ed., 2003 29

Display Screen Screen size: measured diagonally Resolution: minimum identifiable pixel size Approach, 3rd ed., 2003 30

Displays Screen (cont.) How to select a PC display screen: Acceleration and multimedia Monitor size and resolution LCD or CRT Approach, 3rd ed., 2003 31

Acceleration & Multimedia Placing drawing functions into the circuits of the display adapter speeds up rendering on screen. Adding graphics accelerator & video accelerator cards Approach, 3rd ed., 2003 32

Acceleration & Multimedia Approach, 3rd ed., 2003 33

Monitor size & resolution Standard resolutions: 640x480 800x600 1024x768 1280x1024 1600x1200 The higher the resolution, the more material is viewable on screen. Approach, 3rd ed., 2003 34

Displays Screen Approach, 3rd ed., 2003 35

Color and Displays Pixel color is determined by intensity of 3 colors Red Green Blue or RGB RGB: The computer's native color space. It is also the color system for capturing images and displaying them. Human eyes are sensitive to red, green and blue, and all colors are perceived as a combination of the R, G and B. Approach, 3rd ed., 2003 36

CRT Cathode Ray Tube A vacuum tube used as a display screen in a computer monitor or TV. The viewing end of the tube is coated with red, green and blue phosphors dots, which emit light when struck by electrons. Approach, 3rd ed., 2003 37

CRT Approach, 3rd ed., 2003 38

Raster scan Displaying or capturing a video image line by line from left to right. Approach, 3rd ed., 2003 39

LCD Liquid Crystal Display A display technology that uses rod-shaped molecules (liquid crystals) that flow like liquid and bend light. Approach, 3rd ed., 2003 40

LCD (cont.) Approach, 3rd ed., 2003 41

Plasma Display Gas discharge display Uses tiny cells lined with phosphor that are full of inert ionized gas Approach, 3rd ed., 2003 42

Plasma Display (cont.) Approach, 3rd ed., 2003 43

Printers Dots vs. pixels 300-2400 dpi vs. 70-100 pixels per inch Dots are on or off, pixels have intensities Types Typewriter / Daisy wheels obsolete Dot matrix usually 24 pins, impact printing Inkjet squirts heated droplets of ink Laserjet Thermal wax transfer Dye Sublimation Approach, 3rd ed., 2003 44

Printers General Categories Serial Printers (Character Printers) Line Printers Page Printers Approach, 3rd ed., 2003 45

Serial Printer Prints one character at a time moving across the paper. Eg. serial dot matrix printer, with speeds ranging from 200 to 400 cps (90 to 180 lines per minute) Approach, 3rd ed., 2003 46

Dot Matrix Uses hammers and a ribbon to form images out of dots. Forms characters and graphics by impacting a ribbon and transferring dots of ink onto the paper. Approach, 3rd ed., 2003 47

Dot Matrix (cont.) Approach, 3rd ed., 2003 48

Line Printer Print a line at a time from approximately 400 to 2,000 lpm Eg. Line Matrix printer Approach, 3rd ed., 2003 49

Line Matrix Approach, 3rd ed., 2003 50

Line Matrix (cont.) Approach, 3rd ed., 2003 51

Page Printer Prints a page at a time from four to more than 800 ppm. Eg. Laser Printer Approach, 3rd ed., 2003 52

Laser Printer Uses a laser and the electrophotographic method to print a full page at a time. The laser "paints" a charged drum with light, to which toner is applied and then transferred onto paper. Approach, 3rd ed., 2003 53

Laser Printer Approach, 3rd ed., 2003 54

Other Printers Ink jet Dye sublimation Thermal Wax transfer Approach, 3rd ed., 2003 55

Ink Jet Propels droplets of ink directly onto the medium. Makes use of an ink jet cartridge Approach, 3rd ed., 2003 56

Ink Jet Printer Approach, 3rd ed., 2003 57

Dye sublimation printer Produces continuous-tone images that look like photographic film. Also called a "thermal dye printer. The print cartridge contains a cellophane ribbon with panels of dye the same size as the page to be printed. Approach, 3rd ed., 2003 58

Dye sublimation printer (cont.) Approach, 3rd ed., 2003 59

Dye Sublimation Printer Approach, 3rd ed., 2003 60

Thermal wax transfer printer Uses the same printing mechanism as a dye sublimation printer. Instead of using a dye, it melts dots of wax-based ink that adhere to almost any kind of stock, from ordinary paper to complex synthetics and film. Approach, 3rd ed., 2003 61

Thermal wax transfer printer Approach, 3rd ed., 2003 62

Other Scanners Flatbed, sheet-fed, hand-held Light is reflected off the sheet of paper User Input Devices Keyboard, mouse, light pens, graphics tablets Communication Devices Telephone modems Network devices Approach, 3rd ed., 2003 63

Scanner Approach, 3rd ed., 2003 64

Telephone modems Approach, 3rd ed., 2003 65