When I learned programming, the programmer of the CPU had direct memory access. That is, the Z80, the 8086/8088, 6502, and so on. I don't know of any real use of the 186, but at least the 286 introduced "protected mode", which in reality had no impact on the MS/DOS world, besides some extra memory.

Somewhere down the road, O/S like Windows NT, Linux, and so on, used protected mode, and memory became virtual for the (assembly) programmer.

But where was this step really done? Where became protected mode the norm and real mode something for old people with fond memories?