The TOBOL methodology for hardware description from top to bottom level is proposed. Multilevel circuit descriptions can efficiently be provided for diversified purposes. Low-level (such as transistor-level) design information can easily be attached into high-level descriptions. TOBOL utilizes consistent data representations at different levels and allows the integration of circuit descriptions at different levels into a single unified system. Therefore, redundant information is greatly reduced, and efficient access of right functional abstractions of circuits is achieved.