1. Computer Peripherals

2. Web siteWeb site ExamplesExamples 2 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

3. Web siteWeb site ExamplesExamples 3 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

4. Web siteWeb site ExamplesExamples 4 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

5. Web siteWeb site ExamplesExamples 5 Hierarchy of Storage

6. Web siteWeb site ExamplesExamples 6 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 Direct access vs. Sequential access Rotation vs. Linear

7. Web siteWeb site ExamplesExamples 7 Magnetic Disks 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 Head crash Parked heads 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

8. Web siteWeb site ExamplesExamples 8 A Hard Disk Layout

9. Web siteWeb site ExamplesExamples 9 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

10. Web siteWeb site ExamplesExamples 10 Disk Access Times Avg. Seek time average time to move from one track to another Avg. Latency time average time to rotate to the beginning of the sector Avg. Latency time = ½ * 1/rotational speed Transfer time 1/(# of sectors * rotational speed) Total Time to access a disk block Avg. seek time + avg. latency time + avg. transfer time

11. Web siteWeb site ExamplesExamples 11 Exercise A floppy disk is rotating at 300rpm. This disk is divided into twelve sectors, with forty tracks on the disk. The disk is single sided. A block consist of single sector on a single track. Each block contains 200bytes. What is the maximum and minimum latency time for this disk? What is the transfer time for a single block?

12. Web siteWeb site ExamplesExamples 12 Exercise Answer A floppy disk is rotating at 300rpm. This disk is divided into twelve sectors, with forty tracks on the disk. The disk is single sided. A block consist of single sector on a single track. Each block contains 200bytes. i) What is the maximum and minimum latency time for this disk? The maximum latency will occur when the head has just passed the beginning of a block, and a full rotation is necessary to reach the block again. Thus, the maximum latency for this disk is Tmax = 1/300 min. or 1/5 second. Tmin will occur when the head is just over the beginning of the block. Thus Tmin = 0. ii) What is the transfer time for a single block. A complete rotation takes place in 1/300 minute. Since a complete rotation includes 12 sectors, the read time for a single block is Tread = 1/3600 min = 1/60 sec.

13. Web siteWeb site ExamplesExamples 13 Magnetic Disks Data Block Format Interblock gap Header Data Formatting disk Disk Interleaving Disk Arrays Redundant array of independent disks ( RAID) mirrored, striped Disk striping  Process by which data is broken up and stored across several group hard drives Majority logic  fault-tolerant computers Disk Interleaving

14. Web siteWeb site ExamplesExamples 14 Disk Block Formats Single Data Block Header for Windows disk

15. Web siteWeb site ExamplesExamples 15 Alternate Disk Technologies Removable hard drives Disk pack – disk platters are stored in a plastic case that is removable Another version includes the disk head and arm assembly in the case Fixed-head disk drives One head per track Eliminates the seek time Bernoulli Disk Drives Hybrid approach that incorporates both floppy and hard disk technology Zip drives

16. Web siteWeb site ExamplesExamples 16 Magnetic Tape Offline storage Archival purposes Disaster recovery Tape Cartridges 20 – 144 tracks (side by side) Read serially (tape backs up) QIC – quarter inch cartridge (larger size) DAT – digital audio tape (small size) Size typically includes (2:1 compression)

17. Web siteWeb site ExamplesExamples 17 Optical Storage Reflected light off a mirrored or pitted surface CD-ROM Spiral 3 miles long, containing 15 billion bits! CLV – all blocks are same physical length Block – 2352 bytes 2k of data (2048 bytes) 16 bytes for header (12 start, 4 id) 288 bytes for advanced error control DVD-ROM 4.7G per layer Max 2 layers per side, 2 sides = 17G

18. Web siteWeb site ExamplesExamples 18 Optical Storage Laser strikes land: light reflected into detector Laser strikes a pit: light scattered

19. Web siteWeb site ExamplesExamples 19 Layout: CD-ROM vs. Standard Disk CD-ROMHard Disk

20. Web siteWeb site ExamplesExamples 20 CD-ROMs

21. Web siteWeb site ExamplesExamples 21 Types of Optical Storage WORM Disks Write-once-read-many times Medium can be altered by using a medium-powered laser to blister the surface Data stored in concentric tracks, sectored like a magnetic disk CAV Medium-powered laser blister technology also used for CD-R, DVD-R, DVD-ROM CD-RW, DVD-RW, DVD-RAM, DVD+RAM Magneto-Optical Disks

22. Web siteWeb site ExamplesExamples 22 Displays Pixel – picture element Size: diagonal length of screen Resolution (pixels on screen) VGA: 480 x 640 SVGA: 600 x 800 768 x 1024 1280 x 1024 Picture size calculation Resolution * bits required to represent number of colors in picture Example: 16 color image, 100 pixels by 50 pixels 4 bits (16 colors) * 100 * 50 = 20,000 bits

23. Web siteWeb site ExamplesExamples 23 Display Screen Screen size: measured diagonally Resolution: minimum identifiable pixel size Aspect ratio: x pixels to y pixels 4:3 on most PCs 16:9 on high definition displays

24. Web siteWeb site ExamplesExamples 24 Color and Displays Pixel color is determined by intensity of 3 colors – Red Green Blue or RGB 4 bits per color 16 x 16 x 16 = 4096 colors 24 bit color (True Color) 16.7 million colors Video memory requirements are significant!

25. Web siteWeb site ExamplesExamples 25 CRT’s and Text Monitors CRTs (similar to TVs) 3 stripes of phosphors for each color 3 separate electron guns for each color Strength of beam  brightness of color Raster scan 30x per second Interlaced vs. non-interlaced (progressive scan) Text monitors 24 lines x 80 chars A character is the smallest unit on a screen Very little memory required Fast for remote transmissions

26. Web siteWeb site ExamplesExamples 26 Interlaced vs Noninterlaced

27. Web siteWeb site ExamplesExamples 27 Diagram of Raster Screen Generation Process

28. Web siteWeb site ExamplesExamples 28 Display Example

29. Web siteWeb site ExamplesExamples 29 LCD – Liquid Crystal Display Fluorescent light panel 3 color cells per pixel Operation 1 st filter polarizes light in a specific direction Electric charge rotates molecules in liquid crystal cells proportional to the strength of colors Color filters only let through red, green, and blue light Final filter lets through the brightness of light proportional to the polarization twist

30. Web siteWeb site ExamplesExamples 30 LCD Operation

31. Web siteWeb site ExamplesExamples 31 LCDs (continued) Active matrix One transistor per cell More expensive Brighter picture Passive matrix One transistor per row or column Each cell is lit in succession Display is dimmer since pixels are lit less frequently

32. Web siteWeb site ExamplesExamples 32 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

33. Web siteWeb site ExamplesExamples 33 Creating a Gray Scale

34. Web siteWeb site ExamplesExamples 34 Laser Printer Operation 1. Dots of laser light are beamed onto a drum 2. Drum becomes electrically charged 3. Drum passes through toner which then sticks to the electrically charged places 4. Electrically charged paper is fed toward the drum 5. Toner is transferred from the drum to the paper 6. The fusing system heats and melts the toner onto the paper 7. A corona wire resets the electrical charge on the drum

35. Web siteWeb site ExamplesExamples 35 Laser Printer Operation

36. Web siteWeb site ExamplesExamples 36 Laser Printer Operation

37. Web siteWeb site ExamplesExamples 37 Other Computer Peripherals 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