What is the hierarchical structure of computer system?

A computer system consists of two parts: hardware and software. If subdivided by function, it can be divided into seven layers (as shown in the figure). Zero-level is a hard-wired logic level, which is the core of a computer and consists of logic circuits such as gates and flip-flops. The first level is microprogram level. This level of machine language is microinstruction set, and microprograms written by programmers with microinstructions are generally directly executed by hardware. The second level is the traditional machine level. The machine language at this level is the instruction set of the machine, and the programs written by programmers with machine instructions can be explained by microprograms. The third layer is the operating system layer. From the basic function of the operating system, on the one hand, it directly manages the software and hardware resources in the traditional machine, on the other hand, it is an extension of the traditional machine. The fourth level is the assembly language level. The machine language at this level is assembly language, and the program that completes the translation of assembly language is called assembly program. The fifth level is the advanced language level. The machine languages in this episode are all kinds of high-level languages. Compilers are usually used to complete translation of high-level languages. The sixth level is the application language level, which is specially designed to make the computer achieve a certain purpose, so the language at this level is all kinds of problem-oriented application languages. Dividing the computer system into multi-level hierarchical structure according to its functions is conducive to correctly understanding the working process of the computer system and clarifying the position and role of software and hardware in the computer system.