The course ends by naming something it has been describing all along. The air-data computer, the flight management computer, the warning computers, the symbol generators: every one of them is the same kind of machine. This short lesson gives that machine its definitions, explains the buses that connect it to everything else, and then looks back at three systems from earlier modules and reads them as what they always were: computers with peripherals.
What a computer is
A computer is defined as a machine for manipulating data according to a list of instructions. Both halves of the definition matter: the data is whatever the machine is given, and the list of instructions is what makes the same machine an air-data computer in one box and a warning computer in another. The physical split follows directly:
hardware — the physical machine itself, the circuits, processors, memory and wiring that can be touched;
software — the list of instructions the hardware follows, the programs and their data, which weigh nothing and change without a screwdriver.
Buses
A bus is a facility for transferring data between different parts of a computer, both internally and externally: physically it may be wiring, optical fibre or similar, but the word names the function, not the material. Internally, a bus joins the processor to its memory; externally, a bus joins the computer to the equipment around it, its peripherals, and the same idea has appeared in this course wherever one computer fed many consumers, the air-data computer's data bus being the first.