The aim of this work is to develop a new approach in the field of design in the AI domain, where it presents an expert system to design the computer circuits in the various intelligible methods. Both deep and shallow knowledge levels could be involved, and more than one type of knowledge i.e. the explicit, procedural, semantic, and meta knowledge included. This becomes possible by the introduction of a unit for explanations and interpretations that decodes the methodology of reaching solutions, conclusions and recommendations related to each design. The unit is presented in a way similar as analogous to that of the performance of the expert human mind active in the domain of designing these circuits and also adapted to simpler use of the mouse instead of the traditional keyboard. In the presence of such a unit the inference engine becomes a thinking mind of a highly intelligible order that can properly plan for the approach and methodology of the logic deduction to reduce the order of complexity of any circuits concerned and choice of the most appropriate design and cheaper cost. The above mentioned process is carried out in the most accurate and speedy manner. The unit was built using both PROLOG and PASCAL interaction