Aircycle cooling system in aircraft

Why we need aircraft's cabin pressure and temperature to be controlled? At atmospheric condition we have sufficient pressure to breath freely. As the altitude increases pressure drops. Till 8,000 ft altitude the pressure variation won’t affect us but beyond that we will get affect (hypoxia), so in order to have same pressure to breath freely in the cabin of aircraft, we need to go for maintaining the pressure artificially. As like pressure temperature also drops as the altitude increases, but up to certain layer of atmosphere which is stratosphere. Most of the aircraft are operating within Stratosphere. So we need to have a constant temperature in our cabin, so that passengers feel the comfort of their travel. What are the methods in practice for maintaining cabin pressure and temperature? Air cycle system Vapor cycle system Explain Air cycle cooling system of cabin atmosphere control with neat figure? . Left engine ...