Abstract: The present invention is directed to a technique extending the commands, and consequently, the capability of a system editor. Rather than extending the editor with existing editor commands, as in the use of macros, the present invention enables the user to extend the editor using new commands, called transforms. The transforms are written in a standard high level language such as ALGOL, C, COBOL, FORTRAN, or PASCAL. A transform is a new type of command that may be added to a system editor. The transform command is created, compiled, and then stored in a library. When the command is called, an interface in the system editor provides access to the transforms in the library. Transforms are designed so that, to the user, they operate like normal editor commands.