A shell variable is a variable that is available only to the current shell. In contrast, an environment variable is available system wide and can be used by other applications on the system.A shell is the operating system's command interpreter. It processes the commands entered on the command line or read from a shell script file.
The Bernoulli disk drive was named after Daniel Bernoulli (1700-1782), who developed the Bernoulli principle. The device consisted of a specialized floppy disk that had more storage and was faster than the traditional floppy disks of its time.
In using the Bernoulli principle, the disk drive's high-capacity features were attained by pulling the flexible disk toward the head while the disk continued to rotate. The Bernoulli disk drive spun at high velocities and wrote on top of the disk only using a single read/write head.
Bernoulli disks were made of PET “polyester” film, which made them more reliable than traditional hard disks because they were not susceptible to the common cause of hard disk failures at the time, known as head crashes, which happened when the read/write head of a hard disk drive crashed into the rigid rotating platter.
The original Bernoulli disk drive had 5, 10 and 20 MB of storage and was approximately 8.3 by 10.8 inches. The most common was the Bernoulli Box II, which was later replaced by the zip drive (1994) and Iomega’s Jaz drive (1995).
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