The second chapter focus on pragmatic approach
Repetition is the double-edged sword, on the one hand to strengthen program efficiency and increase ease of programming, but on the other hand they are an important cause of Bug, which is self-contradictory on the one hand the computer.
As programmers, we always gather knowledge and make use of, to regulate our knowledge, our knowledge of the use, but unstable and rapid updating of knowledge we must continue to follow up leads, it is very very Headache. If our stuff out of date, it means that we have to learn before we all updates, such a process is very tedious and annoying. So in software engineering, reuse is an important task, reuse someone else's code, write your own knowledge, these are multiplexed. But once our own knowledge base expired, or find someone else's code for an older version, which caused some problems; or the code itself does not meet the requirements, it must be the overall changes to the code. This process is to reuse a negative effect.
The book is divided into repeat it imposed repeat - repeat, environmental requirements - has no intention of repeating the developer did not realize repeated, impatiently repeated - lazy result of duplication between the developers , these mostly repeat in code and documentation, as language problems and automatically generate the issues arising from some duplication, note that these extra things to improve effectiveness.
Also provided in the book of the system design in an orthogonal manner, a so-called orthogonal design is good codes between different functions are orthogonal to each other - that is unrelated. If a system can interfere with each other, then the running time is obviously extremely chaotic, orthogonal benefits are obvious - improve productivity and reduce risk. Improving productivity is due to changes in the system are changed to a partial change, the testing time to a minimum, in addition to promoting reuse and improve the integration of the various components. The risk is low because the code in question is isolated up the system more robust.
I often use these skills in everyday development process which, at the same time reveals the problem is very acute, so the future of the learning process should be more attention to these issues.