KBASE—P is a knowledge—base programming language．It uses KBASE as query language and FD—PROLOG as its procedural host language．The two languages have the same programming paradigm—Horn clause paradigm，and the KBASE—P system accesses disk—resident data in set—at—a—time mode．thus the impedance mismatch problem has been minimized in KBASE—P．KBASE—P manages facts and rules including intermediate results with the help of RDBMS，hence it can manage large amount of data which can be shared by users，and is suitable for large—scale applications．KBASE —P language and its features are described in the paper，and some comparison with related systems are given also．