Direct access: The ability to retrieve data ina random manner rather than having to read all data sequentially until the proper material is reached. For example, disk data can be accessed directly ,instead of sequentially as in a magnetic tpae.

• 直接提取:可以随意提取数据而不须顺序检读数据直至所需资料的性能。例如磁碟可以作直接提取而磁带则是顺序提取的。