The paper describes the design and implementation of INGRES, a relational database management system (DBMS) operational as of March 1976. INGRES supports two high-level nonprocedural data sublanguages and runs on the UNIX operating system for Digital Equipment Corporation PDP 11/40, 11/45, and 11/70 computers. The paper focuses on design decisions related to process structuring, command language embedding, algorithms for interaction processing, access methods, concurrency and recovery control, and data structures for system catalogs and database administration. It also discusses support for integrity constraints, views, and protection, as well as future plans for the system. The paper includes a detailed description of the QUEL query language, the EQUEL precompiler, and the UNIX environment that influenced the design. The process structure of INGRES is explained, along with the functions of each process and the rationale behind the design choices. The paper also covers the data structures and access methods used by INGRES, including the five storage structures available and the Access Methods Interface (AMI) for data access. Finally, it outlines the structure of Process 2, which includes components for lexical analysis, parsing, concurrency control, and query modification.The paper describes the design and implementation of INGRES, a relational database management system (DBMS) operational as of March 1976. INGRES supports two high-level nonprocedural data sublanguages and runs on the UNIX operating system for Digital Equipment Corporation PDP 11/40, 11/45, and 11/70 computers. The paper focuses on design decisions related to process structuring, command language embedding, algorithms for interaction processing, access methods, concurrency and recovery control, and data structures for system catalogs and database administration. It also discusses support for integrity constraints, views, and protection, as well as future plans for the system. The paper includes a detailed description of the QUEL query language, the EQUEL precompiler, and the UNIX environment that influenced the design. The process structure of INGRES is explained, along with the functions of each process and the rationale behind the design choices. The paper also covers the data structures and access methods used by INGRES, including the five storage structures available and the Access Methods Interface (AMI) for data access. Finally, it outlines the structure of Process 2, which includes components for lexical analysis, parsing, concurrency control, and query modification.