Software crisis from the 1960s, to today's traditional software engineering approach, there is a problem: Software is Hard [Martin, 95]. To be honest, the software is a hard bone, and people who truly develop software will have this feel. An app always contains countless intricate details, and software developers organize all of these details to form a procedure that can run normally, this is not a simple matter. Why is this this? Users are easily abstractly expressing their needs, and this abstraction is difficult to translate into program code. Software is not soft, because very simple ideas require a lot of time to implement; software is not soft, because the needs and expectations of users are too difficult; software is not soft, because software is too easy to make users with fantasy. On the other hand, computer hardware technology is developing rapidly. From a mysterious homonym, a mobile chip carrying it will be carried by now with you; When software developers are still looking for "silver bombs" [Brooks, 95] that enhance software development and productivity, hardware development has already increased hundreds of times. Why is that? Hardware engineers can be so efficient because they are very lazy. They will always abide by the ancient training of "Don't go to reinvent the wheel", they try to take advantage of others. Do you see hardware engineers design a dial switch? Do you see hardware engineers design low-pass filtering circuits? Do you see hardware engineers design timers? They have a very good packaging technology that they can package the circuit in a plug-in and only expose the interface. When others want to use, only the interface is used in accordance with the interface, and it is not necessary to fade the implementation inside the cardiac connector. What about software engineers? Before STL became a C standard (even after), each C programmer wrote its own sort algorithm and linked list, and thought it was better than others, it was really sad. OOD can help it "soft" a little. OOD provides us with tools that encapsulate features and complexity on a level. Using OOD, we can create a blackbox software module that hides a lot of complicated things behind a simple interface. The software engineers can then use standard software technology to combine these blackboxes to form the applications they want. Now we usually call them "Component". Class belongings are composed of entities called class (Class), and the classes are combined between the class and classes. A class can hide a lot of details, only a simple interface, which is in line with people like abstract psychology. So, this is a great concept because it gives us the foundation for packaging and reuse, allowing us to see questions from the perspective of the problem, not from the perspective of the machine. The software is initially started from the function library and class library. These two multiplexed forms are actually white boxes. By the 1990s, some people began to develop and sold the real black box software module: Framework and Control. Framers and controls are often limited by platforms and languages. Now the new trend of software technology is a Web Service using SOAP as a transmission medium, which allows the software module to detach from the binding of the platform and language to achieve higher degrees. But think about it, in fact, Web Service is also object-oriented, but it is only to describe the association between classes and classes.
