Computer memory utilizing the principle of magnetic recording first appeared in 1953 in the form of magnetic tape storage. Then, in 1956, the IBM Company in the United States produced a magnetic disk storage. Magnetic disk storage has greater capacity, lower bit cost, and allows random access. For all these reasons, magnetic disk storage has been used ever since as file memory for data processing. Meanwhile, in the 1970s, floppy disk storage was introduced, thereby allowing inputting, outputting, and replacing data. Since the 1980s, floppy disks have been widely used to input, output, exchange, and save data files for personal computers. In the mid-1990s, however, optical disk storage began to replace floppy disks and magnetic tape storage. At present, data files are replaced and saved using CDs and DVDs, and small data exchange can be accomplished using USB flash memory devices.
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