Knowledge Explorer is an interactive tool for organizing knowledge. It helps the user to record, change and search knowledge, and provides extensive error checking to ensure the internal consistency of the knowledge. Interaction with Knowledge Explorer uses the KR language -- simple English-like statements, commands and questions, plus UNIX-like conditionals, loops and methods. A smart menu interface prompts the user for all necessary information, and automatically generates the correct input syntax.Knowledge Explorer defines knowledge as an identification of the facts of reality, using words and sentences. The internal knowledge structure consists of entity-relation hierarchies with space-time dependent events. The principal external knowledge structures are hierarchy outlines, relational databases and transliterated English.Knowledge Explorer object module and KnowledgeBase are available for Windows 98/95/NT/3.x, BSD/OS UNIX, Sun Solaris UNIX, Linux, MS-DOS.