Operating System Overview 2

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2. In order to improve the efficiency of the computer, people came up with the pipeline structure, separated the instructions of the computer into multiple steps, each step of the pipeline can hold an instruction and execute simultaneously. In order to further improve the efficiency of computer, people have designed multi-pipeline, superscalar calculation, super-long instruction word, such as multi-command launch mechanism.

3. Memory access time and capacity

4. We treat all of the computer's hardware as a resource and treat all programs running on the computer as a resource, and then there is the sharing, competition, and protection of resources. In order to distinguish the permissions of the resources that can be used by different programs, we have invented the concept of kernel State (privileged state) and user state. The more resources you can occupy, the higher the society demands on it, and the greater the social responsibility, the more important is the security, real-time and reliability of the kernel-state at this time. Should a program run in the kernel state or the user state? It is also clearly dependent on its requirements for resources and efficiency.

5. What functions should normally be implemented in a kernel state?

From the point of view of computer security, CPU and memory management must be implemented in the kernel state. Diagnostic and test programs require access to all of the computer's resources, otherwise it is difficult to accurately determine whether the computer is normal, so it also needs to be implemented in the kernel state. I/O management, to access a variety of devices and the underlying data structure, is also placed in the kernel-State implementation. While file management can be part of the kernel state, part of the user state.

6. The so-called user state, the kernel state, is actually a state of the processor, not the state of the program.

7. How does the processor restrict the program to use a variety of resources?

To limit the access of a program to a resource, it is necessary to check each instruction executed by the program to complete, and this is the address translation, each instruction issued by the program needs to pass the address translator, and through the control of the address translator, you can restrict the program access to resources. The simplest, when the program is in the kernel state, can bypass the memory address translator and directly execute the relevant instructions.

8. The concept of the process?

Process is the progress of the program, the operating system to manage the process through the process table, the process table contains all the information about the process. Between process and process can realize communication, competition, synchronization and so on. Memory is the process of progress, the purpose of memory management is to achieve data read and write with high efficiency, security, location transparency. A file is an abstraction of an external storage device provided by the operating system, which is the final place where programs and data are stored.

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Operating System Overview 2