Trio is a fully matured and stable set of printf and string functions designed
be used by applications with focus on portability or with the need for
additional features that are not supported by standard stdio implementation. 

There are several cases where you may want to consider using trio: 

   1.Portability across heterogeneous platforms. 
   2.Embedded systems without stdio support. 
   3.Extendability of unsupported features. 
   4.Your native version don't do everything you need. 

WWW: http://www.contactor.se/~dast/trio/