The avionics in our cockpits are getting increasingly more complex. To use these systems more fully it's necessary to not only know how to operate the different equipment, but to understand them. What do they do in operational terms, what interfaces are there with other cockpit devices and what does that permit you to do? New since cockpits of the 20th century are air data computers, AHRS, and magnetometers that a modern GPS requires. EFIS systems, whose PFD’s replace the old 6-pack of instruments and allow you to get rid of the vaccum system, are appearing with more regularity. The MFD side of an EFIS gives you many more display screens, offering more simultaneous information to the pilot. All of these options and more are explained in this manual. The various interfaces are shown here, and the Table of Contents is given to show the specific topics.