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.
If your master cylinder is iron and installed on a currently vacuum assisted Jeep from 1980 to 1974 you can retain your master cylinder if you like, it will bolt directly to the Astro Hydraulic brake booster and you will have one less hydraulic system to bleed on installation.