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DLLs (Dynamic Link Libraries)

A DLL (Dynamic Link Library) is an important component of professional software programs. A DLL is a library file full of information, commands, or procedures needed in a program. In Microsoft Visual C++ 4 you can write a DLL in much the same way as you would an include file. You can include functions that you use frequently. Then you compile it and C++ creates a DLL for you. You can then link the library to a program so that program can use the functions in the DLL.

There are many advantages to using DLLs in your programs. If you ever want to upgrade or improve a program, it is much simpler to just replace a DLL, rather than having to replace an entire program. Also, if put in the SYSTEM directory, DLLs can be used by any Windows application. DLLs are also very helpful to programmers because of their flexibility. All computer programming languages have differences, but many languages can use any DLL. So a programmer using Visual Basic can use a DLL from a program made in C++. This is very helpful because of different coding techniques in different languages.

It is very helpful to a programmer to include a text file or source code explaining a DLL, because DLLs are compiled and not readable to people. Therefore you need to distribute help on which functions are in the DLL and how to use them.

Windows has some very important DLL files that are used to run it. Most of these and other DLLs are all found in the WINDOWS\SYSTEM directory. SHELL32.DLL, KERNEL32.DLL, GDI32.DLL, and USER32.DLL are some of Windows’ main files that it uses to do user input/output, manage memory, and provide a graphical interface that is easy for people to use.