many programs are now developed with add-on support, since it provides a simple way for other developers to extend the functions of the program.
However, not all software programs refer to these extra features as "add-ons." For example, Dreamweaver supports "extensions," which add extra Web development features, while Excel can import "Add-Ins" that provide the user with extra spreadsheet tools. Many programs also support plug-ins, which may be considered a type of add-on.