What is the 4 major components of computer?

Processor Motherboard RAM Power Supply This would be all you would need to get a very Basic OS or BiOS working and "technically" that in itself is a computer system. The fact you would not be able to hear, see or interact with the system is irrelevant in my opinion. This point can be argued that without user control it is of no usefullness, but fundamentally you have a system Booted to a Basic OS (BiOS) that can run processes and compute data, therefore it is a 'Computer'.