Secondary Storage Device Magnetic storage Floppy Disk Hard

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Secondary Storage Device • Magnetic storage ���������� – Floppy Disk – Hard Disk –

Secondary Storage Device • Magnetic storage ���������� – Floppy Disk – Hard Disk – Magnetic Tape : access ��� Sequential , ��� access ���� • Optical Storage ; �������� laser beams ��������� – CDROM , WORM – Optical Disk

History of Storage Device • 1800 s • early 1950 s • 1957 •

History of Storage Device • 1800 s • early 1950 s • 1957 • early 1980 s • The first PCs punch card tape drives -> magnetic drums The first hard drive ( IBM's RAMAC 350 ) 50 x 24” disks to store five megabytes The first 5. 25” hard disk drives , 5 -10 MB Floppy - 8” -> 5” -> 3. 5”

Diskette • size 3. 5 ” , 5 1/4. . . , ” •

Diskette • size 3. 5 ” , 5 1/4. . . , ” • Track , Sector • Single-Sided, Double Sided , Double Density, HD • Format - ������ Diskette ���������� Track, Sector • Cluster ������������� file ������ • FAT ( File Allocation Table (

Harddisk Capacity = Cylinders x Track/Cylinder x Sectors/Track x Bytes/Sector http: //www. pcwebopedia. com/sector.

Harddisk Capacity = Cylinders x Track/Cylinder x Sectors/Track x Bytes/Sector http: //www. pcwebopedia. com/sector. htm http: //www. quantum. com/src/storage_basics/images/S 17 A_2. jpg http: //www. tomshardware. com/geometrie. gif

�������� Disk Capacity (. 1 DISK ���� 1/2 3” , 2 sides , 80

�������� Disk Capacity (. 1 DISK ���� 1/2 3” , 2 sides , 80 Tracks , 18 sectors / Track , 1 sector = 512 bytes Capacity = 512 x 18 x 80 = 2 x 512 x 18 x 80 = 1474560 /1024 = 9216 Bytes / Track = 737280 Bytes/Side = 1474560 Bytes/���� = 1440 Kbytes

����� Harddisk • Fixed • Removable • Portable

����� Harddisk • Fixed • Removable • Portable

������� Harddisk Capacity (. 1 Harddisk ���� 1632 Cylinders , 12 sides , 1

������� Harddisk Capacity (. 1 Harddisk ���� 1632 Cylinders , 12 sides , 1 sector = 512 bytes, 54 sectors / Track 1632 Cylinders = 1632 Track Capacity = 1632 x 54 x 512 x 12 = 541, 458, 432 Bytes 528, 768 KBytes

http: //www. quantum. com/src/storage_basics/c 1_part 1. html

http: //www. quantum. com/src/storage_basics/c 1_part 1. html

CDROM • Compact Disk Read Only Memory • �������� 4. 75 ���� (12 cm.

CDROM • Compact Disk Read Only Memory • �������� 4. 75 ���� (12 cm. ) , ������� > 15�� • Drive Single Speed(1 X) = 150 Kilobyte/S , upto 32 X (@7/7/98) • Interface : SCSI (�� �� ) VS. EIDE(Enhance IDE) • Typical Capacity = 650 Mbytes • Seektime = 100 - 600 ms

Data Compression • �������������������� • ������������ Early to bed, early to rise, makes a

Data Compression • �������������������� • ������������ Early to bed, early to rise, makes a man healthy, wealthy and wise @ # bed, @ # r$, %kes a %n h&, w& and w$ @ = early , # = to , $ = ise , %= ma , & ealthy Compression ratio; 56/30 = 1. 9: 1 (46%) • ������ 2 ������