To build on what foreignrelations said, there are lots of aspects to modern digital electronic computation. Roughly, from CS to Physics, these include (1) the theory and mathematics of computing, (2) the design and construction of computer software, (3) the design and construction of computer systems, (4) the design and construction of digital electronics components, and (5) the theory of electricity and magnetism.
Consider the disciplines (A) computer science, (B) software engineering, (C) computer engineering, (D) electrical engineering, and (E) physics. A rough way to understand what each of these entails (and which represents my estimation) might be the following:
So these disciplines cover to different extents the different aspects of modern digital electronic computing.