Discover the core principles of Human-Computer Interaction (HCI) with this essential guide, perfect for final-year Computer Science and Engineering students and tech enthusiasts. Tailored to align with academic syllabi, this book delves into creating user-centric system software by integrating user behavior and mental models. Explore fundamental software design processes, the role of computation, and advanced computational models of users and systems. With real-world case studies and practical examples, grasp complex concepts, laws, and challenges. This resource keeps you updated on cutting-edge developments in ubiquitous and wearable devices, emphasizing that human needs always come first. Enhance your understanding with dedicated chapters on user-centric systems and research/development challenges.