虚拟存储器主要是为了解决扩大主存容量的需求而设置的，一般页式虚拟存储器规定把主存和辅存都分成大小相同的页，程序运行时需要访问辅存内容，可把包括有关单元的一个辅存页面调入主存一个空页中，其后CPU根据程序的局部性原理，可多次从主存中取出需要的有关指令和数据，大大提高了存取有关数据的速度，虚拟存储器最关键的是虚存页面调入主存时CPU如何知道调入主存何页?虚实页面地址是依靠(1)实现页面地址转换的。这种转换是采用(2)实现的。

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Traditional　structured　analysis　techniques　focus　upon　the　flow　of(71)within　a　system.　Object　-　oriented　analysis　emphasizes　the　building　of　real　-　world　models.　It　examines　requirements　from　the　perspective　of　the　classes　and　objects　found　in　the　vocabulary　of　the(72)domain.

Traditional　system　design　method　emphasizes　the　proper　and　effective　structure　of　a　complex　system.　Object　-oriented　design　method　encompasses　the　process　of　object　-oriented　decomposition　and　a(73)for　depicting　both　logical　and　physical　as　well　as　static　and　dynamic　models　of　the　system　under　design.

Object　-　oriented　programming　is　a　method　of　implementation　in　which　programs　are　organized　as　cooperative　collections　of　objects,　each　of　which　represents　an(74)of　some　class,　and　whose　classes　are　all　members　of　a　hierarchy　of　classes　united　via(75)relationships.

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A　typical(66)language　contains　an　applicative　sub-language　which　approximates　the　mathematical　abstractions　of　"timeless"　functions　applied　to　"spaceless"　values,　where　the　actual　operation　sequences　and　use　of　storage　space　during　expression　evaluation　are　organized　behind　the(67).　In　this　setting,　values　are　data　structures　of　low　volume,　typically　a　few　computer　words　or　less,　which　means　that　an　illusion　of　spacelessness　can　be　realized　by　having(68)results　during　expression　evalution　stored　at　the　discretion　of　the　language　implementation,　and　effecting　parameter(69)and(70)operations　through　value　copying.