Definition of a Function. A function is a relation for which each value from the set the first components of the ordered pairs is associated with exactly one value from the set of second components of the ordered pair. Okay, that is a mouth full.
Master cylinder without booster. Single bore master cylinders: These unboosted hydraulic Master Cylinders are actuated by foot effort, via the brake pedal. The brake pressure is related to actuation force and depends on the piston bore size: the smaller the bore, the higher the pressure.
The brake booster is designed to create a greater braking force from minimum pedal effort, using a difference in atmospheric pressure and the engine's manifold vacuum. It increases the pedal force 2 to 4 times depending on the size of the diaphragm. The brake booster is located between the brake pedal and the master cylinder. When pressure is applied to the brake pedal, pressure is exerted on the booster air valve. With pressure created by the booster the master cylinder is applied.