【文章內(nèi)容簡(jiǎn)介】 lasses or methods with userdefined attributes. This can be useful for documentation and can have some effects on pilation (for example, marking methods to be piled only in debug builds). ? Full access to the .NET base class library, as well as easy access to the Windows API (if you really need it, which won’t be all that often). ? Pointers and direct memory access are available if required, but the language has been designed in such a way that you can work without them in almost all cases. ? Support for properties and events in the style of Visual Basic. ? Just by changing the piler options, you can pile either to an executable or to a library of .NET ponents that can be called up by other code in the same way as ActiveX controls (COM ponents). ? C can be used to write dynamic Web pages and XMLWeb services. Most of the above statements, it should be pointed out, do also apply to Visual Basic .NET and Managed C++. The fact that C is designed from the start to work with .NET, however, means that its support for the features of .NET is both more plete, and offered within the context of a more suitable syntax than for those other languages. While the C language itself is very similar to Java, there are some improvements: in particular, Java is not designed to work with the .NET environment. Before we leave the subject, we should point out a couple of limitations of C. The one area the language is not designed for is timecritical or extremely high performance code—the kind where you really are worried about whether a loop takes 1,000 or 1,050 machine cycles to run through, and you need to clean up your resources the millisecond they are no longer needed. C++ is likely to continue to reign supreme among lowlevel languages in this area. C lacks certain key facilities needed for extremely high performance apps, including the ability to specify inline functions and destructors that are guaranteed to run at particular points in the code. However, the proportions of applications that fall into this category are very low. 二、 database development process Based on information engineering information systems planning database is a source of development projects. These new database development projects is usually in order to meet the strategic needs of anizations, such as improving customer support, improve product and inventory management, or a more accurate sales forecast. However, many more database development project is the bottomup approach emerging, such as information system user needs specific information to plete their work, thus beginning a project request, and as other information systems experts found that anizations need to improve data management and begin new projects. Bottomup even in the circumstances, to set up an enterprise data model is also necessary to understand the existing database can provide the necessary data, otherwise, the new database, data entities and attributes can be added to the current data resources to the anization. Both the strategic needs or operational information needs of each database development projects normally concentrated in a database. Some projects only concentrated in the database definition, design and implementation of a database, as a followup to the basis of the development of information systems. However, in most cases, the database and associated information processing function as a plete information systems development project was part of the development. System Development Life Cycle Guide management information system development projects is the traditional process of system development life cycle (SDLC). System development life cycle is an anization of the database designers and programmers information system posed of the Panel of Experts detailed description, development, maintenance and replacement of the entire information system steps. This process is because Waterfall than for every step into the adjacent the next step, that is, the information system is a specification developed by a piece of land, every piece of the output is under an input. However shown in the figure, these steps are not purely linear, each of the steps overlap in time (and thus can manage parallel steps), but when the need to reconsider previous decisions, but also to roll back some steps ahead. (And therefore water can be put back in the waterfall!) Figure 4 on the system development life cycle and the purpose of each stage of the product can be delivered concise notes. The system development life cycle including each stage and database developmentrelated activities, therefore, the question of database management systems throughout the entire development process. In Figure 5 we repeat of the system development life cycle stage of the seven, and outlines the mon database at each stage of development activities. Please note that the systems development life cycle stages and database development steps 一一對(duì)應(yīng) exists between the relationship between the concept of modeling data in both systems development life cycle stages between. Enterprise Modeling Database development process from the enterprise modeling (system development life cycle stage of the project feasibility studies, and to choose a part), Organizations set the scope and general database content. Enterprise modeling in information systems planning and other activities, these activities determine which part of information systems need to change and strengthen the entire anization and outlines the scope of data. In this step, check the current database and information systems, development of the project as the main areas of the nature of the business, with a very general description of each term in the development of information systems when needed data. Each item only when it achieved the expected goals of an