The system keeps a font table containing all the fonts that applications can use. The system chooses a font from this table when an application calls the CreateFont or CreateFontIndirect function. There can be up to 253 entries in the table.
A font resource is a group of individual fonts representing characters in a given character set that have various combinations of heights, widths, and pitches. You can load font resources and add the fonts in each resource to the operating system font table by using the AddFontResource function. To remove a font resource from the font table, you can use the RemoveFontResource function.
After you add a font resource to the font table, you can use the individual fonts in the resource. In other words, the CreateFont function takes the fonts into account when it tries to match a physical font to the specified logical font. (Fonts in the table are never directly accessible to an application. They are available only through the CreateFontIndirect and CreateFont functions, which return the handles of the fonts, not their memory addresses.)
Whenever your application adds or removes a font resource, it should inform all other applications of the change by sending a WM_FONTCHANGE message to them. Use the following call to the SendMessage function to send the message to all windows.
SendMessage(HWND_BROADCAST, WM_FONTCHANGE, 0, 0);
You can use the GetProfileString function to search the [Fonts] section of the WIN.INI file for the list of fonts that the user has used Control Panel to install.