We have already described an incompressible plasma in chapter 6. In this chapter we generalise the equations to describe a compressible plasma. We implemented the algorithms in the code so that simulations can be run on a broad range of parallel computers using the Message Passing Interface (MPI) [60]. We tested the code on some simple magnetohydrostatic test cases and on the Orszag-Tang vortex. Also, we simulated flow past a cylinder with an imposed far-field magnetic field.