The questions necessary for a developer to create client-server applications using the Firebird DBMS, which is a development of the Borland Interbase 6 DBMS, are considered. It contains an overview of the concepts and models of the client/server architecture, as well as practical recommendations for working with Firebird client libraries. The features of SQL data types, the Data Manipulation Language (DML), as well as the syntax and operators of the Data Definition Language (DDL) are described in detail. Much attention is paid to the description of transactions and tips on their use in application development are given. Describes client- and server-side programming, writing triggers and stored procedures, creating and using database events, handling errors in server code, and much more. The material is accompanied by numerous examples, tips and practical recommendations. For database developers