The book covers the topic of Embedded Computers for Spacecraft. We need to define and explore some terms, starting with "embedded computer." We'll look at its cpu, memory, and I/O. The Space environment is harsh, and hard on computer components. We'll review these effects, and see what additional requirements they place upon the system.
Just as embedded computers are special cases of computers in general, then space flight embedded computers are a special case of embedded. They are embedded computers which operate in a challenging environment.
I make the assumption you know a bit of computer architecture, how instructions are executed, and how cache works. If not, get a good book or two on computer architecture. There's some in the references. That's our starting point.
