This textbook was written with two primary objectives. The first is to introduce the C program- ming language. C is a practical and still-current software tool; it remains one of the most popular programming languages in existence, particularly in areas such as embedded systems. C facilitates writing code that is very efficient and powerful and, given the ubiquity of C compilers, can be easily ported to many different platforms. Also, there is an enormous code-base of C programs developed over the last 30 years, and many systems that will need to be maintained and extended for many years to come. The second key objective is to introduce the basic concepts of software design. At one-level this is C-specific: to learn to design, code and debug complete C programs. At another level, it is more general: to learn the necessary skills to design large and complex software systems. This involves learning to decompose large problems into manageable systems of modules; to use modularity and clean interfaces to design for correctness, clarity and flexibility.