Windows CE file filters are Component Object Model (COM) objects that exist on the desktop computer. They are loaded and called by Windows CE Services, which is an application that runs on the desktop computer and enables connection with a Windows CE–based device. When a file is copied to or from the Windows CE–based device to the desktop computer by using Windows CE Services, Windows CE Services checks to see whether a file converter is registered for the file type being transferred. If so, Windows CE Services loads the file filter and issues a request to convert the file. This all takes place on the desktop computer (the client side of the link), where most processing between the desktop computer and the device takes place.
If a file is being exported from a Windows CE–based device to the desktop computer, it is copied in its original form to the desktop computer, converted by the file filter, and stored on the desktop computer. In much the same way, if a file is being imported to a Windows CE–based device, it is converted by the file filter, and then the file is copied to the Windows CE–based device.
Windows CE file filters are dependent on the Mobile Devices folder that is provided by Windows CE Services. Only files that are moved to and from a Windows CE–based device by users dragging them to the Mobile Devices folder are converted. If a file is transferred to a Windows CE–based device by any other method, such as downloading a file from the Internet by using Pocket Inbox, the file filter is not loaded and the file is not converted.