What is COMCOM,Component object mode is the Component Object model. What is called a "model" is that COM is a programming specification (non-specific code) that allows us to write language-independent, extensible, internal changes that are completely transparent to the user, and that support distributed (for users, remote and local COM components use should be undifferentiated) code. COM Components
- A product written in accordance with COM standards is called a COM component. It is the implementing body of the COM standard.
- Following COM standards,
a COM component can be seen as a collection of interfaces (where the interface is not a function of the general sense, but something similar to a class)
- The client is dealing with COM, only through the interface (that is, COM is an interface-oriented programming, which isolates the user and the specific implementation, to achieve the scalability and the stability of the change to the user), it can be said that the interface defines COM.
- Several functions are included in each interface, and the client uses the COM component by first acquiring the interface and then calling the function.
- The composition of a COM component can be understood as a COM component that contains several interfaces, each containing several functions.
Requirements for COM components
1. Dynamic Linkthe ultimate goal of COM is to enable the user to dynamically replace the component during the run of the application, which requires the component to be dynamically linked to the program (such as in-process components, which are implemented in the form of DLLs)
2, encapsulation ofthe implementation details of COM should be encapsulated in order to ensure the stability of the interface and realize the dynamic substitution of components in the application. for encapsulation, there are the following limitations on components(1) The component hides the programming language it uses. And any language should be able to use COM. (2) components must be published in binary form. In order to hide the COM programming language, they must be compiled, linked, and immediately ready to use. (3) Compatibility of components. The new version of the component should not affect the use of the old version of the program. (4) The components are transparent on the network. The customer's use of local COM and remote COM should be exactly the same. In Summary, the COM component is composed of executable code published in the form of a DLL or an EXE. COM components are dynamically linked and have client-transparent encapsulation.
com is not what1, COM is not a specific language, but a programming specification. 2, COM is not the implementation of dll,com to take advantage of DLL dynamic link ability, but not simple equivalent. 3. com is not a collection of functions. COM components feature a broad set of functions with a simple function. In addition to providing functional functions to customers, COM also provides a series of thread synchronization policies (suites), event callback mechanisms (connection points), and so on.
COM Librariescom is not just a set of specifications, it does contain some concrete implementations. The specific implementation of the COM library provides very useful component management for all customers and Components
COM Technology Components
