Answer: – One is the standalone scrollbar control. This one has its own window handle, and consequently can be given focus and all those other fun things you can do with window handles. To manipulate them, pass the handle to the scrollbar control to the appropriate scrollbar function (SetScrollInfo, for example) and pass SB_CTL as the nBar parameter to indicate that you have a scrollbar control.

The other type is the horizontal or vertical scrollbar (or both) attached to a window by virtue of having the WS_HSCROLL and/or WS_VSCROLL style. These are nonclient scrollbars and are not controls. They are just decorations added to some other window. You can’t give them focus since they aren’t windows in their own right. To manipulate them, pass the handle to the containing window to the appropriate scrollbar function and pass SB_HORZ or SB_VERT as the nBar parameter to indicate that you want to manipulate the nonclient horizontal or vertical scrollbar.

The Common Dialog Box Library provides a creation function and a structure for each type of common dialog box. To use a common dialog box in its simplest form, you call its creation function and specify a pointer to a structure that contains initial values and option flags. After initializing the dialog box, the dialog box procedure uses the structure to return information about the user input. You can also customize a common dialog box to suit the needs of your application.

Although a Print Setup dialog box is available, it has been superseded by the Page Setup dialog box. Applications should use the Page Setup dialog box rather than the Print Setup dialog box.

All common dialog boxes are modal, except the Find and Replace dialog boxes. Modal dialog boxes must be closed by the user before the function used to create the dialog box can return. The Find and Replace dialog boxes are modeless; the function returns before the dialog box closes. If you use the Find and Replace dialog boxes, you must also use the IsDialogMessage function in the main message loop of your application to ensure that these dialog boxes correctly process keyboard input, such as the TAB and ESC keys.

An ActiveX control is a component program object that can be re-used by many application programs within a computer or among computers in a network. The technology for creating ActiveX controls is part of Microsoft’s overall ActiveX set of technologies, chief of which is the Component Object Model (COM). ActiveX controls can be downloaded as small programs or animations for Web pages, but they can also be used for any commonly-needed task by an application program in the latest Windows and Macintosh environments. In general, ActiveX controls replace the earlier OCX (Object Linking and Embedding custom controls). An ActiveX control is roughly equivalent in concept and implementation to the Java applet.

An ActiveX control can be created in any programming language that recognizes Microsoft’s Component Object Model. The distributed support for COM is called the Distributed Component Object Model (DCOM). In implementation, an ActiveX control is a dynamic link library (DLL) module. An ActiveX control runs in what is known as a container, an application program that uses the Component Object Model program interfaces. This re-useable component approach to application development reduces development time and improves program capability and quality. Windows application development programs such as PowerBuilder and Microsoft Access take advantage of ActiveX controls.

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