07 External Memory - MetaLab
07 External Memory - MetaLab 07 External Memory - MetaLab
Continue..• Information is retrieve from a CD/CD-ROM by a low-powered laser housed in anoptical-disk player or drive unit• The laser shines through the clear polycarbonate while a motor spins the disk past it• The intensity of the reflected light of the laser changes as it encounters a pit• The areas between pits is called lands• A land is smooth surface which reflects back at higher intensity• The change between pits and lands is detected by a photosensor and converted into adigital signal.• The sensor tests the surface at regular intervals.• The beginning or end of a pit represents a 1, when no change in elevation occurbetween intervals, a 0 is recorded.
Continue..• Data on CD/CD-Rom is organized in a singlespiral track in a sequence of blocks• Sectors near the outside of the disk are the samelength as those near the inside.• Hence info is packed evenly across the disk insegments of the same size and these are scannedat the same rate by rotating the disk as a variablespeed.• The pits are then read by the laser as a constantlinear velocity (CLV).
- Page 1 and 2: William StallingsComputer Organizat
- Page 3 and 4: Magnetic Disk• Disk - a circular
- Page 5 and 6: Inductive Write MR Read
- Page 7 and 8: Disk Data Layout
- Page 9 and 10: Disk Layout Methods Diagram
- Page 11 and 12: Multiple zone recording (MZR)• To
- Page 13 and 14: Removable or Not• Removable disk
- Page 15 and 16: Multiple Platters
- Page 17 and 18: Classification of disk based on hea
- Page 19 and 20: Disk performance parameters• The
- Page 21: Optical Storage CD-ROM• Originall
- Page 25 and 26: Other Optical Storage• CD-Recorda
- Page 27 and 28: DVD - technology• Multi-layer•
- Page 29 and 30: Magnetic Tape• Tape system use th
Continue..• Data on CD/CD-Rom is organized in a singlespiral track in a sequence of blocks• Sectors near the outside of the disk are the samelength as those near the inside.• Hence info is packed evenly across the disk insegments of the same size and these are scannedat the same rate by rotating the disk as a variablespeed.• The pits are then read by the laser as a constantlinear velocity (CLV).
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