Fundamentals of hydraulics and pneumatics are presented in this manual, prepared for regular navy and naval reserve personnel who are seeking advancement to Petty Officer Third Class. The history of applications of compressed fluids is described in connection with physical principles. Selection of types of liquids and gases is discussed with a background of operating temperature ranges, contamination control techniques, lubrication aspects, and safety precautions. Components in closed- and open-center fluid systems are studied in efforts to familiarize circuit diagrams. Detailed descriptions are made for the functions of fluidlines, connectors, sealing devices, wipers, backup washers, containers, strainers, filters, accumulators, pumps, and compressors. Control and measurements of fluid flow and pressure are analyzed in terms of different types of flowmeters, pressure gages, and values; and methods of directing flow and converting power into mechanical force and motion, in terms of directional control valves, actuating cylinders, fluid motors, air turbines, and turbine governors. Also included are studies of fluidics, trouble shooting, hydraulic power drive, electrohydraulic steering, and missile and aircraft fluid power systems. Illustrations for explanation use and a glossary of general terms are included in the appendix.