This book presents the issues in the design, implementation, selection, and use of computer files for external storage of data. An analytical approach is followed throughout so that the concepts learned can be applied not only to the examples shown in the book but to any of the wide variety of file structures found in practice, and to those that will appear in the future. Scope we present the file topics in a setting of transaction processing. Transaction processing introduces modularity into file access programs, and this modularity is beneficial in presentation as well as in actual system design. Performance of entire transactions can be evaluated, both for centralized and distributed systems.