The history of computers is the history of abstraction. Early calculating machines, like Leibniz's Stepped Reckoner, hid the calculating process from the user, but still required the user to input numbers and provided numbers as output. With the advent of Turing-complete machines, we reached the first major abstraction level of using symbols to represent things. A paper by Federico Gobbo and Marco Benini titled, The Minimal Levels of Abstraction in the History of Modern Computing (PDF format), goes a bit further. It takes up the notion of thinking about modern machines in terms of the relation between operators, programmers, users, and computers as an interconnected informational organism or inforg, so that we can consider further levels of abstraction that have emerged. From the paper:
This point (symbolic representation) was the big change of the modern era, where the universal computing machinery started to hide some symbolic interpretation of numbers through abstractions and organisations in parallel, where each LoO (Level of Organization) is the externalisation of the correspondent LoA (Level of Abstraction). The more computers developed, the more information got hidden and needed reconstruction on demand: to correctly explain this historical process, we [propose] here a constructive based formalism
The authors consider the gradual increase in abstraction as more and more details about the underlying computation are hidden from the human elements of the inforg. First, the Von Neumann Machine, then the concept of an Operating System and applications. Then applications are abstracted into a visible part (the GUI) and an invisible part. Additional abstractions are introduced for interactivity, multitasking, distributed processing. As the abstractions accumulate, the separation between humans in the inforg (the programmer and the user) increase. How will robotics and AI affect this evolving relationship? For more historical background on their ideas, see From Computing Machineries to Cloud Computing: The Minimal Levels of Abstraction of Inforgs through History (PDF format).