The Windows API Library FilesThe Dynamic Link Library (DLL) files that make up the Windows API are commonly located in the Windows SYSTEM subdirectory. These files are found on every PC that is running Windows, so you don't have to worry about including them if you create a set of setup disks for distribution. The three major Windows DLLs are USER32.DLL, KERNEL32.DLL, and GDI32.DLL. Several smaller DLLs are known as extension DLLs and provide functions in addition to those found in the three major DLLs. Some useful extension DLLs include the following: COMDLG.DLL DLLLZ32.DLL VERSION.DLL APIGID.DLL COMCTL32.DLL MAPI32.DLL NETAPI32.DLL ODBC32.DLL WINMM.DLL The following sections discuss in some detail the primary purposes of each DLL as well as some examples of the functions they provide. USER32.DLLThe USER32.DLL library file contains functions that relate to managing the Windows environment, such as
The following list outlines some of the functions of the USER32 library:
GDI32.DLLThe GDI32.DLL library file (the Graphics Device Interface library) contains functions that help manage output to different devices, especially the screen. Following are some of the functions in GDI32:
KERNEL32.DLLThe KERNEL32.DLL library contains functions that manage the low-level operating system functions. These functions include
Here are some of the functions in the KERNEL32 library:
The Extension DLL LibrariesThe extension DLLs are libraries added to Windows when the functionality of Windows has changed in some way, usually with the addition of new features to the operating system. Instead of completely rewriting the operating system whenever a new feature is added, a new DLL is added to the system that includes the functions that add the new feature to the operating system. For example, when Microsoft added multimedia capabilities to Windows, it created a new DLL that includes the multimedia functions, WINMM.DLL. The major extension libraries that are a part of Windows are
These are the library files and extensions to the Windows operating system you will call when you write programs that access the Windows API. After you learn how to call these libraries from your Visual Basic applications (the subject of the next section), you can tap the full power of the Windows environment. |
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