Computer-based Natural Language Processing (NLP) is the key to enabling humans and their computer-based creations to interact with machines using natural languages (English, Japanese, German, etc.) rather than formal computer languages. NLP is a major research area in the fields of artificial intelligence and computational linguistics. Commercial natural language interfaces to computers have recently entered the market and the future looks bright for other applications as well. This report presents an overview of: (1) NLP applications; (2) the three basic NLP approaches; (3) various types of grammars; (4) difficulties in semantic processing of phrases and sentences; (5) knowledge representation (KR); (6) types of syntactic parsing; (7) the relationship among semantics, parsing, and understanding; (8) NLP system types, including question answering, natural language interface (NLI), computer aided instruction (CAI), discourse, text understanding, and text generation systems; (9) the functions, approaches, capabilities, and limitations of NLP systems developed for research purposes; (10) current research NLP systems; (11) the approximate price, developer, purpose, and features of some commercial NLP systems; (12) the state of the art of NLP systems; (13) problems and issues related to language use, linguistics, conversation, processor design, database interfaces, and text understanding; (14) research required in these areas; (15) the principal United States and foreign participants in NLP, and the principal U.S. government agencies funding NLP research; (16) future trends and expectations; and (17) further sources of information. A 39-item bibliography and a glossary are also provided. (Author/ESR)