OLE / ActiveX

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Windows NT 32-bit applications are capable of performing object linking and embedding (OLE) with other 32-bit applications and 16-bit applications. The OLE is not limited to just other 32-bit applications.

Object linking and embedding makes creating compound documents possible. An object from one application can be embedded or linked into another application’s data. By embedding an object, the data can be edited in its native format. Linking an object enables changes to the original object to be reflected in the host document.

Figure 5.5 shows an example of a linked Excel chart in Microsoft Word.

Because the spreadsheet is linked into the Word document, any changes made to the original Excel spreadsheet are reflected in the Word document when it is opened. Likewise, double-clicking on the linked chart can make changes to the Excel chart easily. This will lead to the chart being edited in Microsoft Excel and the original source data document will be opened for editing.

ActiveX, like OLE, is based on the Component Object Model. ActiveX specializes in embedding control into web-based sites, enabling web pages to respond to events instead of remaining static at all times.

ActiveX adds new innovations to the Internet. ActiveX controls enable web developers to implement many features in a web page, including the following:

• Designating a life span on an embedded object on a web page. After an object’s deadline passes, it no longer displays on the page. This works very well for limited-time offers on a web page.
• Adding additional animation to a web page.
• Adding preprogrammed ActiveX objects to a web page that are readily available instead of developing them yourself. In fact, you need no knowledge whatsoever about how the control was actually developed.
• Adding increased functionality to web pages, more like that commonly found in dialog boxes, such as combo boxes and scroll bars.

The ActiveX Control Pad can be used to easily add prefabricated ActiveX controls into your web pages. You can download the ActiveX Control Pad for free from Microsoft’s web site.

When a web page that has an ActiveX control within it is accessed, the user should be warned that an ActiveX control is about to be downloaded to his or her system. Depending on the security level set in Internet Explorer, the user is then asked whether the download should proceed. If the control makes use of Authenticode, a digital certificate displays (see Figure 5.6).

The digital signature information is stored within the control itself. The end user has the option of downloading or not downloading the control. The user can also set the automatic downloading of any further controls from the same developer.




ActiveX controls have the potential to be quite harmful. Be wary of installing ActiveX controls if you are uncertain of their origin. It is possible for damage to occur to your system if a “suspect” ActiveX control is downloaded. One of the best ways of protecting yourself is by setting your security level in Internet Explorer. On the Security tab of the View Options in Internet Explorer you can set the safety level (see Figure 5.7). Internet Explorer 3.02 changed the default level to a high safety level. This prevents any ActiveX control from being downloaded to your system, because they may be a danger to your computer.