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Application of PowerBuilder User Objects in Developing Distributed Programs Wang Li-fu, Li Hua- ming 0　Introduction The object-oriented methods and tools have been recommended in developing software. The User object of PowerBuilder simulates the class in object- oriented conception. It is one of the most flexile objects to develop the performance of PowerBuilder. By using PowerBuilder , the developer can develop the function of the primary object function, add new user-defined components and enhance the reuse of code. Moreover, we can develop the component by C++ to improve the speed-sensitive parts, and insert them to the PowerBuilder program. There are two kinds of PowerBuilder objects :one of them is the visual objects, they can be used to communicate between application program and users; the other kind of them is the nonvisual objects, it has no visual component , and is mainly used to encapsulate and complete the certain kinds of business logic. User Objects——as the other PowerBuilder objects , contain some of properties, such as event、instance variables、user object functions etc. Generally, a nonvisual object represents the one class in system analysis. We dont intend to discuss how to define instance variables and to write the function of user object , you can refer the PowerBuilder documents. Usually we use non-visual object to perform the PowerBuilder distributed application. Distributed computing is a natural outgrowth of the development of network computer systems that use the client / server architecture. It allows you to get the most in the client / server architecture. The conception of distributed computing is closely connected with RPC ( remote procedure call ). RPC is the technique that the client program can call processes ( functions) of the remote Computer, and get the process result ( function return value) . PowerBuilder shield many details of RPC and makes it easy to develop the server and the client application. 1　The Application of User Ob