Computer Science is concerned with understanding, designing, implementing and using computing systems, ranging in scale and complexity from the tiny components of a single processor to the globe-spanning internet. The core concepts of computing have their roots in mathematics, logic, and engineering, such as what it means to compute, what can or cannot be computed, and how computers work. It also concerns the practical techniques of programming computers to solve real and difficult problems, and there are many links to other subjects, from electronics, physics, and mathematics, to biology, psychology, linguistics, and sociology. This intellectually challenging subject underpins the core technologies of the 21st century, and can be a route to many different career paths.