What are the three basic parts of a pneumatic system?

A - Compressor: a pump which compresses air, raising it to a higher pressure, and delivers
it to the pneumatic system (sometimes, can also be used to generate a vacuum).
B - Check valve: one-way valve that allows pressurized air to enter the pneumatic system,
but prevents backflow (and loss of pressure) into the compressor when it is stopped.
C - Accumulator: stores compressed air, preventing surges in pressure and relieving the
duty cycle of the compressor.
D - Directional valve: controls the flow of pressurized air from the source to the selected
port. Some valves permit free exhaust from the port not selected. These valves can be
actuated either manually or electrically (the valves typically provided in the FIRST kits use
dual solenoids to change the direction of the valve, based on input signals from the control
system).
E - Actuator: converts energy stored in the compressed air into mechanical motion. A
linear piston is shown. Alternate tools include rotary actuators, air tools, expanding
bladders, etc.