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| Introduction | ||
It is possible to use functions from other DLL files, as long as you
know the declarations to access the functions. The developer of the DLL
must provide a detailed set of documentation, telling other developers
how to create a declaration for the functions contained within that DLL. But what are DLL's? DLL stands for Dynamic-Link-Library. A DLL is a file containing executable
code, like an EXE or COM file. Instead of containing a complete program,
a DLL contains functions that can be used by other running programs. These
functions might contain code to provide services not built into Windows,
for example the ability to perform some kind of data compression. A Windows
program would use these functions after it begins executing. It does this
by opening the DLL file and calling functions from it. The programmer
must already know what these functions are when the program's code is
written. Windows APIs are the function calls that are the fundamental building
blocks of Windows programming. Although the term API actually refers to
the complete set of function calls, the term API is also often applied
to just a single defined function call of the entire API. So it is often
said, "I made an API call," or, "I want my program to call
an API that does such and such..." |