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ITEC 1011 Introduction to Information Technologies 10. Computer Peripherals – Part II Chapt. 10.

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Presentation on theme: "ITEC 1011 Introduction to Information Technologies 10. Computer Peripherals – Part II Chapt. 10."— Presentation transcript:

1 ITEC 1011 Introduction to Information Technologies 10. Computer Peripherals – Part II Chapt. 10

2 ITEC 1011 Introduction to Information Technologies Plan Tape drives Optical disks Displays

3 ITEC 1011 Introduction to Information Technologies Rationale Magnetic tape is used as secondary storage when… Offline storage is acceptable or preferred Capacity requirements exceed that of floppy disks Sequential access is adequate Magnetic tape is used for… Off-site data preparation Backup

4 ITEC 1011 Introduction to Information Technologies Terminology Backup The act of copying files to a second medium (typically disk or tape) as a precaution in case the first medium fails It is important in computing to backup your files regularly

5 ITEC 1011 Introduction to Information Technologies Types of Tape Drives Two types: Reel-to-reel Used on mainframe computers Cartridge Used on PCs In either case, the tape can be removed from the drive (i.e., the tape drive supports offline storage) When a tape is loaded in a tape drive and is ready to be accessed, the tape is mounted

6 ITEC 1011 Introduction to Information Technologies Reel to Reel Tape Drive

7 ITEC 1011 Introduction to Information Technologies Tape Reels

8 ITEC 1011 Introduction to Information Technologies Tape Reel Specifications Reel diameter: 10 ½ Tape width: ½ Tape length: 2400 feet Number of tracks: 9 Drive has nine read/write heads 9 bits of data are read/written at a time (8 data + parity) Each group of nine bits is called a frame Data density/capacity 1600 frames/inch 2400 x 12 x 1600 = 46,080,000 bytes/reel 6250 frames/inch 2400 x 12 x 6250 = 180,000,000 bytes/reel

9 ITEC 1011 Introduction to Information Technologies Nine-track Tape Layout Physical record Inter-record gap 1 byte of data (8 data bits + parity) Track 1 Track 9 ½

10 ITEC 1011 Introduction to Information Technologies Tape Cartridge

11 ITEC 1011 Introduction to Information Technologies Types of Tape Cartridges QIC (Quarter Inch Cartridge) DAT (Digital Audio Tape)

12 ITEC 1011 Introduction to Information Technologies QIC (Quarter Inch Cartridge) Pronounced: quick Introduced in 1970s Popular format for backing up personal computers Two general classes Full-sized, 5¼ (also called data cartridge) Mini-cartridge, 3½ Capacities up to 10 GB

13 ITEC 1011 Introduction to Information Technologies DAT (Digital Audio Tape) Tape width: 8 mm or 4 mm Uses helical scan technique to record data (like VCRs) Capacities to 24 GB (4 mm) or 40 GB (8 mm)

14 ITEC 1011 Introduction to Information Technologies Plan Tape drives Optical disks Displays

15 ITEC 1011 Introduction to Information Technologies Operation Uses light generated by lasers to record and retrieve information Information is stored by varying the light reflectance characteristics of the medium Available in read-only (CD-ROM) and read/write formats

16 ITEC 1011 Introduction to Information Technologies CD-ROM CD-ROM stands for compact disc, read- only memory Evolved from audio CDs Disk size: 120 mm (5¼) Capacity: 550 MB

17 ITEC 1011 Introduction to Information Technologies CD-ROM vs. Magnetic Disk CD-ROMMagnetic Disk One spiral track (3 miles long!) Multiple tracks of concentric circles Constant bit densityVariable bit density Disk speed varies (CLV, constant linear velocity) Disk speed constant (CAV, constant angular velocity) Constant transfer rate Capacity: 550 MBCapacity: varies

18 ITEC 1011 Introduction to Information Technologies CD-ROM Data Organization 270,000 blocks of 2048 bytes each (typically) 270, = 552,960,000 bytes Extensive error checking and correction (e.g., bad regions of the disk flagged) Substantial overhead for error correction and identifying blocks Capacity can be as high as 630 MB

19 ITEC 1011 Introduction to Information Technologies CD-ROM Drive Specs SpeedSeek TimeTransfer Rate 1x600 ms150 KB/s 4x ms600 KB/s 8x ms1.2 MB/s 16x ms2.4 MB/s 24x ms3.6 MB/s 32x ms4.8 MB/s

20 ITEC 1011 Introduction to Information Technologies Pits and Lands (1 of 2) Data are stored as pits and lands These are burned into a master disk by a high powered laser Master disk is reproduced mechanically by a stamping process Data surface is protected by a clear coating Data are read by sensing the reflection of laser light A pit scatters the light A land reflects the light

21 ITEC 1011 Introduction to Information Technologies Pits and Lands (2 of 2) Laser Land Reflected light Laser Pit Scattered light

22 ITEC 1011 Introduction to Information Technologies CD-ROM Read Process Laser diode Prism Light detector Land Pit Transparent protective layer More detail

23 ITEC 1011 Introduction to Information Technologies

24 ITEC 1011 Introduction to Information Technologies Laser Diodes

25 ITEC 1011 Introduction to Information Technologies Read/Write Variations WORM (Write Once, Read Many) Magneto Optical

26 ITEC 1011 Introduction to Information Technologies WORM Disks and Drives WORM = Write-once, read many Also called CD-R, for CD Recordable Begin with blank CDs WORMs drives are used to write the CD The write process is irreversible Many standards, some disks may be read on standard CD-ROM drive, others may not Applications Infrequent data distribution Small quantities For large quantities, cheaper to have CR-ROMs manufactured

27 ITEC 1011 Introduction to Information Technologies Magneto Optical Disk may be written, read, and rewritten Write process is preformed at high temperature Combines features of optical and magnetic technology Data are stored as a magnetic charge on the disk surface During reading, the polarity of the reflected light is sensed (not the intensity)

28 ITEC 1011 Introduction to Information Technologies Plan Tape drives Optical disks Displays

29 ITEC 1011 Introduction to Information Technologies Types of Displays Two main types CRT (cathode ray tubes) LCD (liquid crystal display) Related terms Monitor or screen A display is often called a monitor or screen However, the term monitor usually refers to the entire box, where as screen often implies just a sub-assembly within the box

30 ITEC 1011 Introduction to Information Technologies Colour Displays CRT displays each pixel is composed of three superimposed dots: red, green, and blue Hence, RGB display The three dots are created by three separate beams Ideally, the three dots should converge at the same point, however, in practice there is a small amount of convergence error, and this makes the pixels appear fuzzy LCDs Colour is created by filtering/blocking different frequencies of light

31 ITEC 1011 Introduction to Information Technologies Operation of a CRT Display A CRT display contains a vacuum tube At one end are three electron guns, one each for red, green, and blue At the other end is a screen with a phosphorous coating The three electron guns fire electrons at the screen and excite a layer of phosphor Depending on the beam, the phosphor glows, either red, green, or blue

32 ITEC 1011 Introduction to Information Technologies CRT Display

33 ITEC 1011 Introduction to Information Technologies Operation of an LCD Two sheets of polarizing material with a liquid crystal solution between them An electric current passes through the liquid, causing the crystals to align so that light cannot pass through them Each crystal, therefore, acts like a shutter, either allowing light to pass through or blocking the light

34 ITEC 1011 Introduction to Information Technologies Liquid Crystal Display

35 ITEC 1011 Introduction to Information Technologies Pixels A Pixel is a picture element a single point in a graphic image A graphics display is divided into thousands (or millions) of pixels arranged in rows and columns The pixels are so close together, they appear connected The number of bits used to represent each pixel determines how many colours or shades of grey can be represented For a B&W (black and white) monitor, each pixel is represented by 1 bit With 8 bits per pixel, a monitor can display 256 shades or grey or 256 colours (Note: 2 8 = 256)

36 ITEC 1011 Introduction to Information Technologies Display Size Usually specified in inches Value cited is the diagonal dimension of the raster -- the viewable area of the display E.g., a 15 monitor 15

37 ITEC 1011 Introduction to Information Technologies Resolution Resolution is the number of pixels on a screen display Usually cited as n by m n is the number of pixels across the screen m is the number of pixels down the screen Typical resolutions range from… 640 by 480 (low end), to 1,600 by 1,200 (high end)

38 ITEC 1011 Introduction to Information Technologies Video RAM Requirements Total number of pixels is n m Examples = 307,200 pixels 1,600 1,200 = 1,920,000 pixels Video RAM required equals total number of pixels times the number of bits/pixel Examples = 2,457,600 bits = 307,200 bytes = 300 Kbytes 1,600 1, = 46,080,000 bits = 5,760,000 bytes = 5,625 Kbytes = 5.49 Mbytes

39 ITEC 1011 Introduction to Information Technologies Resolution Bits per pixel 8 bit16 bit24 bit 640 x x x x x x Video RAM (KB) Per Image See previous slide for calculations

40 ITEC 1011 Introduction to Information Technologies Aspect Ratio Aspect ratio is the ratio of the width to height of a display screen For a 640 by 480 display, the aspect ratio is 640:480, or 4:3 Related terms Landscape The width is greater than the height Portrait The height is greater than the width

41 ITEC 1011 Introduction to Information Technologies Dot Pitch Dot pitch is a measure of the diagonal distance between phosphor dots (pixels) on a display screen One of the principal characteristics that determines the quality of a display The lower the number, the crisper the image Cited in mm (millimeters) Typical values range from 0.15 mm to 0.30 mm Note Dot pitch, as specified, is the capability of the display For a particular image, dot pitch can be calculated as…

42 ITEC 1011 Introduction to Information Technologies Dot Pitch Image Example Q: What is the dot pitch of an image displayed on a 15 monitor with a resolution of 640 by 480? A: Z 1.Z = ( ) 1/2 = mm = inch Dot pitch= 15 / 800 inches = inches = / mm = mm Notes:

43 ITEC 1011 Introduction to Information Technologies Dot Pitch Illustrated Pixel mm

44 ITEC 1011 Introduction to Information Technologies Exercise – Dot Pitch Image Q: What is the dot pitch of an image displayed on a 19 monitor with a resolution of 1,280 by 1,024? Skip answer Answer

45 ITEC 1011 Introduction to Information Technologies Exercise – Dot Pitch Image Q: What is the dot pitch of an image displayed on a 19 monitor with a resolution of 1,280 by 1,024? A: Answer Dot pitch= 19 / inches = inches = / mm = 0.30 mm Note: Z = ( ) 1/2 =

46 ITEC 1011 Introduction to Information Technologies Dot Pitch Image Table Resolution Display Size x x x x x x Note: Dot pitch figures in mm (millimeters)

47 ITEC 1011 Introduction to Information Technologies Dot Pitch Example Q: A 19 CRT monitor, made by Vapour Hardware Inc., has a dot pitch specification of 0.28 mm. What is the highest resolution at which this monitor will reliably operate? A: Discussion: Just read the value above from the dot pitch image table. For a 19 monitor, a 1,280 by 1,024 image has a dot pitch of 0.30 mm. The monitors dot pitch specification exceeds this, therefore, the monitor will work fine at this resolution. However, a 1,600 by 1,200 image on a 19 monitor requires a dot pitch of 0.24, which is beyond the capability of the example monitor. 1,280 by 1,024

48 ITEC 1011 Introduction to Information Technologies Exercise – Dot Pitch Skip answer Answer Q: A 17 CRT monitor has a dot pitch specification of 0.30 mm. What is the highest resolution at which this monitor may operate? A:

49 ITEC 1011 Introduction to Information Technologies Exercise – Dot Pitch Q: A 17 CRT monitor has a dot pitch specification of 0.30 mm. What is the highest resolution at which this monitor may operate? A: 1,024 by 768 Answer

50 ITEC 1011 Introduction to Information Technologies Interlacing Interlacing is an image drawing technique whereby the electron guns draw only half the horizontal lines with each pass The odd lines are drawn on the 1 st pass, the even lines are drawn on the 2 nd pass A non-interlaced imaged is completely drawn in one pass Lets see…

51 ITEC 1011 Introduction to Information Technologies Interlacing Animation Non-interlaced scanningInterlaced scanning Electron beam on (drawing) Electron beam off (retracing)

52 ITEC 1011 Introduction to Information Technologies Uses of Interlacing TVs use interlaced scanning Computer monitors (CRTs) use non- interlaced scanning

53 ITEC 1011 Introduction to Information Technologies Retracing Retracing is the act of repositioning the electron beam The beam must undergo horizontal retrace (once per line) and vertical retrace (once per image) Vertical retrace Horizontal retrace

54 ITEC 1011 Introduction to Information Technologies Scan Frequency Horizontal scan frequency The frequency with which an electron beam moves back-and-forth The rate of drawing each line in an image Typical range: kHz Vertical scan frequency The frequency with which an electron beam moves up- and-down Also called vertical refresh rate, refresh rate, vertical frequency, vertical scan rate, or frame rate The rate of drawing images Typical range: Hz

55 ITEC 1011 Introduction to Information Technologies Multi-scan Monitors A multi-scan monitor can adjust to the horizontal and vertical scan frequencies of the video signal produced by the interface Also called multi-sync, multi-frequency, or variable-frequency monitors

56 ITEC 1011 Introduction to Information Technologies Video Frequency The frequency at which pixels are drawn on the display Specified as a maximum capability of the monitor Also called video bandwidth Typical ranges MHz

57 ITEC 1011 Introduction to Information Technologies Video Frequency vs. Resolution and Frame Rate Video Frequency > Resolution Frame Rate Example:Daewoo CMC-1703B specifications: Video frequency = 85 MHz Max resolution = 1280 by 60Hz Note: = 78,643,200 = 78.6 MHz

58 ITEC 1011 Introduction to Information Technologies Display Properties in Windows Right click on the desktop (display) and select Properties Click Settings to determine/change the setting for Colors and Screen area (Resolution) To determine/change screen refresh rate, click on Advanced, then click on Adapter Next 2 slides

59 ITEC 1011 Introduction to Information Technologies Note: Varies on different systems

60 ITEC 1011 Introduction to Information Technologies Note: Varies on different systems Demo

61 ITEC 1011 Introduction to Information Technologies Colour Control Three ways to control colour 1.Selecting from a predefined palette 2.Individually control red, green, and blue 3.Individually control colour and brightness Colour is also called chrominance (C) Chrominance consists of hue and saturation Brightness is also called luminance (Y) Most applications support all three techniques Next 2 slides

62 ITEC 1011 Introduction to Information Technologies Predefined Palette

63 ITEC 1011 Introduction to Information Technologies Custom Control Demo

64 ITEC 1011 Introduction to Information Technologies Video Interfaces (1 of 2) Composite video Definition: a video interface in which all the colour and sync information is contained in one signal Contrast with RGB TVs in North America use composite video RGB (Red, Green, Blue) Definition: a video interface in which the red, green, and blue signals, and the horizontal and vertical sync signals, are separate Computer monitors use RGB

65 ITEC 1011 Introduction to Information Technologies Video Interfaces (2 of 2) S-video A technology for transmitting video signals over a cable by dividing the video information into two separate signals: one for colour (chrominance, C), and one for brightness (luminance, Y) Also called Y/C video Televisions (internally) are designed for separate luminance and chrominance signals Computer monitors are designed for separate red, green, and blue signals

66 ITEC 1011 Introduction to Information Technologies RGB Video Standards A variety of standards exist for delivering RGB signals to a video display monitor Developed and consolidated by VESA (Video Electronics Standards Association) Examples VGA – video graphics adapter SVGA – super-VGA XGA – extended graphics adapter

67 ITEC 1011 Introduction to Information Technologies VGA/SVGA/XGA Pinouts PinSignal 1Red 2Green 3Blue 4ID bit 2 5Ground 6Red return 7Green return 8Blue return 9- 10Sync return 11ID bit 0 12ID bit 1 13Horizontal sync 14Vertical sync 15- DE15 connector

68 ITEC 1011 Introduction to Information Technologies S-video Pinouts PinSignal 1Ground 2 3Y (luminance) 4C (Chrominance) 4-pin mini-DIN connector

69 ITEC 1011 Introduction to Information Technologies Flat Panel Displays A very thin display screen Most flat panel displays use LCD technology Other technologies ELD (electro-luminescent display) Gas plasma display

70 ITEC 1011 Introduction to Information Technologies Active-Matrix Display A type of liquid crystal display in which the image is refreshed more frequently than in conventional (passive matrix) displays Most common type of active-matrix display is known as TFT (thin-film transistor) The terms active matrix and TFT are used interchangeably

71 ITEC 1011 Introduction to Information Technologies Thank you Next topic


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