How to transform software architecture in order to meet user requirements? How to enhance the system software without moving the structure of the system from its original design? How to make the transformation phase very effective and ‘simple-sharp’ one? We frequently evaluate and manipulate system architecture to gain better software. This paper identifies the steps of transforming software architecture by performing six modular operators; excluding-augmenting-splitting-substituting-inverting porting. We categorize useful design operator that affect modular software architecture. The paper is based on the study of Islamic Astronomy Software, Moon Calculator (MoonC) that been use in Space Physics Laboratory, Department of Physics, University of Malaya.