For years, magnetic technology has dominated the mass storage arena. The most common example in use today is the magnetic disk, in which a thin spinning disk with magnetic coating is used to hold data. Read/write heads are placed above and/or below the disk so that when the disk spins, each head traverses a circle, called a track, around the disk’s upper or lower surface. By repositioning the read/write heads, different concentric tracks can be accessed. In many cases, a disk storage system consists of several disks mounted on a common spindle, one on top of the other, with enough
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Due to volatility and limited size of a computer’s main memory, most computers have additional memory devices called mass storage (or secondary storage) systems, including magnetic disks, CDs, DVDs, magnetic tapes, and flash drives (which will be discuss on next article). The advantage of mass storage systems over main memory include less volatility, large storage capacities, low cost, and in many cases, the ability to remove the storage medium from the machine for archival purposes.
The term on-line and off-line are often used to describe devices that can be either attached to or detached from a machine. On-line means that
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As you will learn in Data Manipulation subject later, it is convenient to design main memory systems in which the total number of cells is a power of two. In turn, the size of the memories in early computers were often measured in 1024 (2^10) cell units. Since 1024 is close to the value 1000, many in the computing community adopted the prefix kilo in reference to this unit. That is, the term kilobyte (KB) was used to refer to 1024 bytes. Thus, a machine with 4096 memory cells was said to have a 4KB memory (4096 = 4 *
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