Software program developers need to go from beginning to ending and understand source code of the program and other software attributes. The software complexities and length of the program exceedingly affects many design level quality attributes, specifically Simplicity, Testability and software Maintainability. Incomplete design of any software generally leads to misunderstanding and ambiguities and therefore to gives faulty design and development results. This is mainly seeming and appears

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... ng to the absence of it's an appropriate observation, design and development control. However, high level design and program simplicity are very necessary and one of the vital attributes of the system development cycle. This research paper highlights the impact and significance of design level software simplicity in common and as a one of the most useful key factor or index of software quality assurance and testing. In this research work principally there are three major efforts are made. As a first contribution, a valuable relationship between software design quality factor simplicity and related object oriented design properties, this has been set up. In the second contribution, using design level corresponding metrics a simplicity evaluation model for object oriented software is developed. Subsequently, the developed simplicity model has been rationally authenticated by means of experimental data try-out.