Chapter 3: A Tour Through COS 3.1 The Location of COS in the HST Focal Plane 3.2 The Optical Design of COS 3.2.1 External Shutter 3.2.2 The Apertures and Aperture Mechanism 3.2.3 Gratings and Mirrors: The Optics Select Mechanisms 3.2.4 Detectors 3.2.5 On-board Calibration Lamps 3.3 Basic Instrument Operations 3.3.1 Target Acquisitions 3.3.2 Data Taking: TIME-TAG and ACCUM 3.3.3 Wavelength Calibration 3.3.4 Typical Observing Sequences 3.3.5 Data Storage and Transfer 3.4 COS Illustrated 3.5 COS Quick Reference Guide