General principles of software quality

There is no free lunch in the world , Even if there is , The taste must not be so good . But software development is far from advanced cooking technology , And the software quality is so different . The general principle of software quality is to improve quality to reduce development costs .

Understanding this principle depends on understanding a key fact that is easy to observe ： Improve production efficiency and quality The best way is to reduce the time spent on such code rework , Whether the reworked code is made up of requirements 、 The design change is caused by debugging . The industry average productivity of software products is about per person per day 10 To 50 Line final delivery code （ Include all non coding expenses ）.

Knock out 10 To 50 Line of code is just a matter of minutes , So how do you spend the rest of your day ？

This productivity data looks so low , Part of the reason is that this industry average includes the time spent by non programmers “ Number of lines of code per day " In the calculation of . Testers 、 project manager 、 The time of administrative support is included . Non coding work such as requirements development and architecture design , It will also be taken into account in the calculation . But these are not the main reasons why time is so amazing .

One of the largest activities of most projects is debugging and correcting code that doesn't work properly . Debugging and related refactoring or other rework work , In the traditional immature software development cycle, it may consume about 50％ Time for . Just avoid introducing errors , You can reduce the debugging time , To increase productivity . therefore , The most obvious way to shorten the development cycle is to improve the quality of products , Total rework time .

More quality assurance work can reduce the error rate , But it will not increase the total cost of development .

IBM A similar conclusion was reached in a study of ：

The development plan time of the software project with the least defects is the shortest , And has the highest development productivity , Eliminating software defects is actually the most expensive and time-consuming software work .

This conclusion is also true on the smallest scale .1985 In, someone carried out a study , requirement 166 Professional programmers write programs according to the same specifications , The average program they write is 220 Line code , The average time spent by each person is slightly less than 5 Hours . What is very surprising is , Those programmers who spend less time writing the most mistakes , Those programmers who spend more or less time writing programs contain significantly fewer errors .

With the traditional “ Code test debug " comparison , Advanced software quality plans may be more cost-effective . This plan reallocates the resources invested in debugging and reconfiguration to the early quality assurance work , And the effect of early work on product quality will be more obvious than later work , So put time into the preliminary work , It can save programmers more time in later work .

The final effect of this method is that the software has fewer defects , Shorter development time , Lower cost .