Keywords broadcast tricks advanced COM components can applications files programs
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PC since its inception, the hardware has undergone countless changes, the CPU from the original Intel 8086 to
Now it is only more than 10 years piii full street. Microsoft's Windows operating system from the initial
Version 1.0 is now ready to launch WIN2000, the most installed OS on the desktop system.
As a software developer, the use of the C++,delphi package including the Visual basic,visual
Many development environments, including the latest Borland C + + Builder, for Windows development
Application. It should be said that the current development conditions and a number of years ago than has been greatly improved.
If you have developed a 16-bit Windows program, you probably know that in order to read a file, I
Have to use a small assembly to invoke the DOS routine, or use windows that was not yet exposed
Function: _lopen (). In the Win32 environment, all you have to do is call
:: CreateFile () to get a file handle, of course, if you use MFC or Owl.
Things that you can do more simply. But in general, programmers still have to start from scratch
Start writing each line of code for the application.
But the situation has changed: Microsoft has proposed C O M (Component Object Model,
The "Component Object Model") concept can also be translated, and in the latest windows95/98 to
And win NT4 are increasingly used in it: we have reason to believe that in the near future, C O M
will be the most common way to build your application, if you are interested in this technology, you may wish to refer to this
I hope you can learn the knowledge you want to know from it. If you are already a C O m veteran, also welcome
You criticize me.
This article is written for C + + programmers. In introducing the concept, I try not to put the WIN32 API
Knowledge, so that you can see the essence of C O m more clearly. All the examples are
Compiled with Microsoft Visual c++5 (SP3).
Generally speaking, an application is always composed of a single binary file. In the past, if
This program needs to make some improvements, it is necessary to modify the source code, and then compile, claim the new file,
Then replace the original file. Now, let's look at the problem in a whole new way: the original
The entire EXE executable file, divided into functionally different but relatively independent parts, put him
They assemble, compose the program, and compose the software. After the release of future programs, if you are aware of the need
To make changes to him, just replace the problematic or build that needs to be upgraded. Even
You can do this without affecting the normal operation of the program to replace the parts. If you are familiar with
Windows programming, you might think: DLL seems to be what you say: can be dynamic, moving
State connection. In fact, COM is fully leveraging the flexibility of the Win32 DLL to truly
Implemented on the Windows platform.
What are the advantages of this? First: Users generally want to be able to customize the applications they use,
and component technology is inherently customizable, so users can use it to better meet their needs
One of the components to replace the original one. Second, because the components are relative to the application independent
Components, we can use the same component in different programs without creating any problems, soft
The reusability of the pieces can be greatly enhanced. Thirdly, with the increase of network bandwidth and its importance,
Distributed Web applications undoubtedly become an increasingly important point of purchase in the software market. Component
The pricing structure can simplify the process of developing such applications.
So, what is com exactly? It is a specification that shows how to build a dynamically-variable component.
He defines a number of clients (a term that refers to a program that requires some kind of component) to be interoperable.
The standard that a component must follow, the COM specification is a set of document shapes that sets the standard for the component schema
-Type specifications. COM is published in the form of a Win32 dynamic-link library (DLL) or an executable file
(EXE) in the form of published executable code.
COM components are dynamically connected, and COM components are completely language-independent. Also, COM groups
Can be published in binary form. COM components can also be promoted without prejudice to old customers.
into a new version.
You can now think that COM can provide services that are similar to those in C + +. But the class is the base
Source code, COM is not. But here are some misconceptions about com: first,
COM is not a computer language. Comparing COM to a computer language (such as C + +, VB) is
There's no point. Second, do not compare the DLL and COM, because COM technology is the use of
DLL's dynamic linking capability, and now the general view is that using DLL dynamic
The best way to link ability is com.
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