While editing can still be done via SEU, the simple green screen editor (even though syntax checking is not supported for features introduced from IBM i V7R1 onward), a long progression of tools has been developed over time. Some of these have included CODE/400 and Visual Age for RPG, which were developed by IBM. Currently the preferred editing platform is IBM's Websphere Development Studio client, (WDSc) now named RDi (Rational Developer for i), which is a customized implementation of Eclipse. Eclipse, and therefore RDi, runs primarily on personal computers and other devices. IBM is continually extending its capabilities and adding more built-in functions (BIFs). It has the ability to link to Java objects, and i5/OS APIs; it can be used to write CGI programs with the help of IBM's Cgidev2 Web toolkit, the Cozzi cozTools (a collection of RPG and CGI routines for RPG IV), CGILIB, the RPG Toolbox, and other commercial Web-enabled packages. Even with the changes, it retains a great deal of backward compatibility, so an RPG program written 37 years ago could run today with little or no modification.