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半导体内存只有在计算机电源开通时才工作。硬盘、磁带和软盘系统是以磁存储为基础的,这种存储方法的特点是寿命有限,可交换性差,这是由于磁头与盘片之间的直接接触所造成的。此外。鉴于对更大容量的需求的不断增长,具有比软盘容量更大的数据存储媒体,变得愈发吸引人了。 在电子数据存储中光学媒体当前所占的份额仍很有限(见图1.3)。 近年来,我们已看到利用光学媒体对数据存储和传播所起的作用在不断增长。在光学媒体中存储和检索数据不发生物理接触而是利用一束激光,就像音频CD一样(见图1.4)。光学媒体具有很长的寿命期望值(30—100年),容易进行数据交换,且具有很高的数据存储容量。这就说明了为什么人们对光存储的兴趣日益增加(见图1.5)。
Semiconductor memory only works when the computer’s power is on. Hard disk, tape, and floppy disk systems are based on magnetic storage. This storage method is characterized by limited life and poor interchangeability due to the direct contact between the head and the disk. In addition. Given the ever-increasing demand for larger capacities, data storage media having more capacity than floppy disks have become even more appealing. The current share of optical media in electronic data storage is still limited (see Figure 1.3). In recent years, we have seen an increasing use of optical media for data storage and distribution. Instead of physically accessing and retrieving data in an optical medium, a laser is used, just like an audio CD (see Figure 1.4). Optical media have long life expectancy (30-100 years), easy data exchange, and high data storage capacity. This explains why people are increasingly interested in optical storage (see Figure 1.5).