I don't think that's such a good example. Doctors don't build medical equipment, nor do they do anything in that class. Coders write software and the operating

I don't think that's such a good example. Doctors don't build medical equipment, nor do they do anything in that class. Coders write software and the operating system, compiler, VM, etc. that they use as tools are also software. If we want to compare with the doctor, we can say that a programmer doesn't need to understand how junctions of doped semi-conductors behave, nor how that can be used to build gates, nor how those gates can be used to build a processor. The lowest level ever required is to understand the behaviour of the processor (how that behaviour comes to be is a black box). This is because that's the lowest abstraction layer that absolutely doesn't leak.