principle 4 : high-quality software is possible
Although our industry is saturated with examples of software systems that perform poorly, that are full of bugs, or that otherwise fail to satisfy users’ needs, there are counter examples.large-scale software systems can be built with very high quality, but for a steep price tag: on the order of $1000 per line of code. One such example is IBMS on-board flight software for NASAS space shuttle. Totaling approximately three million lines of code,the rigorous software development process resulted in less than one error found per ten thousand lines of code after product release.
As a developer, be aware of the techniques that have been demon-strated to increase quality considerably. These include involving the customer(Principle 8), prototyping(to verify requirements prior to full-scale development; Principles 11 through 13), keeping the design simple (Principle 67), inspections(Principle 98), and hiring the best people ( Principles 130 and 131). As a customer, demand excellence but be aware of the high costs involved
尽管我们的行业充斥着性能差，漏洞多更甚者无法满足用户需求的软件例子，但也有反例。大型软件系统可以以非常高的质量构建，但价格昂贵：每行代码1000美元。一个这样的例子是用于NASAS航天飞机的IBMS机载飞行软件。总共约300万行代码，严格的软件开发过程导致产品发布后每万行代码中发现的错误少于一个。
作为开发人员，需要注意极大提高软件质量被证明是可能的。这些包括涉及客户（原则8），原型设计（在全面开发之前验证要求;原则11至13），保持设计简单（原则67），校验检查（原则98）和雇用最优秀的人员（原则） 130和131）。作为客户，需求卓越，但要注意所涉及的高成本。
