HCI notes cover the fundamental principles and concepts of the field of human-computer interaction. These notes explore the design, development, and evaluation of interactive systems that enable effective and efficient user experiences. Key topics include user-centered design, interaction modalities, usability engineering, cognitive psychology, and emerging trends in HCI such as ubiquitous computing and multi-modal interfaces. The notes provide a comprehensive overview of HCI, equipping students and professionals with the knowledge and skills to create intuitive and engaging digital products and services that cater to the needs and preferences of end-users. These notes serve as a valuable resource for both introductory and advanced studies in the dynamic field of HCI.