This application note describes techniques for creating software applications using the Memory Management Unit (MMU) of the ST9+. In addition, it provides useful hints on using the ST9+ C Compiler. A description of the main characteristics of the ST9+ MMU will be given. Then, the C compiler will be briefly described, emphasizing the Memory Management Unit aspects. Finally, the subject matter is developed using examples for a ROMless and a ROM microcontroller, the ST92R195 and the ST92195 respectively.