This document discusses the effect of Human Computer Interfacing (HCI) on society, economy, and culture. It explores the principles of design in HCI, such as perception, continuity, closure, symmetry, similarity, familiarity, trichromatic system, luminance, and the 'pop out' effect. It also covers behavior models in HCI, including predictive models like Fitts' Law and descriptive models like Guiard's Model. Additionally, it delves into information processing in HCI, highlighting the role of humans as components and the use of GOMS (Goals, Operators, Methods, and Selection) in design. References are provided for further reading.