The C interface provides a powerful way to incorporate legacy code that is already in C form or for applications that require the highest possible performance. An example of the latter is the basic AOLserver page fetching module, which is designed for optimal performance. Although the module is statically linked into the AOLserver, it is structured in the same way as any other C module, including a single initialization function that calls AOLserver C API function to register itself. You can also add new Tcl commands using the C interface.