I suspect this is more difficult than fathomed by Michael Kjörling and the OP.
The OP seems to think of the operation of a CPU as a straight, single time-line, where tasks are executed sequentially. And Michael Kjörling re-inforces that impression by remarking that any given core is executing strictly one instruction per cycle, sequentially.
This is certainly incomplete on the microscopic level (present day pcs have multiple CPUs) and unhelpful on the meso/macro-scopic levels.
We describe all complex systems in terms of macroscopic variables; sometimes this is because those are only the variables we have access to, but their usefulness is not principally that of easy access. We do not describe a gas by stating positions and velocities of all particles involved, but use instead pressure/volume/temperature/entropy.
By the same token, we do not characterize a machine state by means of CPU instructions, but in terms of tasks and services being carried out. As such, there are at any one given time multiple processes running and exchanging information, often acting in concert (and sometimes even in competition, sadly) to achieve a common goal.
The equivalent of pressure/volume/entropy/temperature in computer science are the abstraction layers, simplified representations of the tasks performed by a machine, irrespective of the actual realizations of the agents performing the tasks. ALs are present all over computer science, from HALs to the OSI layers, and so on.
Asking for a step-by-step representation of a pc operation is like giving up strange attractors in the theory of turbulence in favor of a multi-particle fluid description. Or trying to decode human genome by studying chemical bonds. One builds on the other, but the new abstraction layer affords insights unimaginable otherwise.