软件维护工作越来越受到重视，因为它的花费常常要占软件生存周期全部花费的(28)%。其工作内容为(29)。为了减少维护工作的困难，可以考虑采取的措施是(30)。而软件的可维护性包含(31)。所谓维护管理主要指的是(32)等。

(120)

(118)

(119)

(117)

(115)

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.

(114)

(113)

(110)

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.