This is a little 'BASIC' intepreter I've written, check it out if you feel like (It's old, 2 months). Written in standard C, very portable. In fact it compiles without modification in DOS and UNIX (the different versions only have different makefiles, because of the different operating systems).

UNIX version (source only):
http://bozos.sourceforge.net/files/cnasica-0.1.tar.gz

DOS version (including exe and source):
http://bozos.sourceforge.net/files/cnasica.zip