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Ch13. 13.1 Secondary Storage Devices. Also called “Backing storage” Store data, operating system and application software Non-volatile Measured by access time and data transfer rate Can be classified into 2 main types Magnetic storage devices Optical storage devices. Secondary storage
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13.1 Secondary Storage Devices • Also called “Backing storage” • Store data, operating system and application software • Non-volatile • Measured by access time and data transfer rate • Can be classified into 2 main types • Magnetic storage devices • Optical storage devices
Secondary storage device CPU Main Memory
The Speed of a Secondary Storage Device Data transfer rate Searching speed Reading/writing process Access time
Different Concept of Magnetic Storage Device and Optical Storage Devices
13.2 Magnetic Storage Devices • Most of them read/write enabled • E.g. floppy disks, hard disks, magnetic tapes
Floppy Disks • Only have 1.44 MB • Usually used for backing up and transferring a small amount of data • Direct access mode
Hard Disks • Have one or more circular disks • Called platters • Each platters have a large number of tracks • Direct access mode • Fast, durable, high-capacity storage medium
The time of access data file The data transfer rate The rotational speed The speed rotations of disk plates The time of access data file The movement of read/write heads
Magnetic Tapes • Sequential access mode • For back up purpose • Latest magnetic type = DAT • Storage over 72GB • Low cost
13.3 Optical Storage Devices • Most of them --> store data, instructions • E.g CD-Rom, CD-R, DVD ,DVD-R
Compact Disc Read-Only Memory (CD-ROM) • Data stores and accesses by via red laser • The content --> permanently • Data represented by pits and lands
The mechanism of a CD-ROM drive P.78 PICTURE
CD-ROM drive • The speed --> its data transfer rate • direct proportion • Measured relative to use 2x, 4x, 8x, etc • To describe the speeds
CD-R and CD-RW • Both CD-R drives and CD-RW drives • Allow to write data • CD-RW can rewrite data many times over
Digital Versatile Disc (DVD) • Store up to 17GB of Data • Can saved movies and libraries of multimedia files • Many different variations • DVD+R, DVD-R, DVD+RW, DVD-RW, DVD-RAM • The concept of write data on to DVD same with a floppy disk • To copy, modify and delete files • The speed to write over 8x
High-definition digital versatile disc (HD DVD) and Blu-ray Disc • For storing digital media • Used the blue-violet laser technology • Are incompatible