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In this note, many terms about operating systems don't need to know too much. As long as there is a general grasp of the concept and understanding of the operating system, the end of the note is taken as an example of the Windows2000 Personal Computer operating system, so that The function of the operating system has a further understanding of the structure.
Ø Concept of operating system
Let us start from the computer system, then introduce the operating system.
A computer system is a system that can receive and store information by user, automatically perform data processing and outputting result information.
Computer systems include hardware subsystems and software subsystems. The hardware system is an entity that the computer is working, which includes a central processor (CPU), main memory, outer memory, and various types of input and output devices; software systems ensure that the computer system is coordinated by user-specified requirements, it Includes a variety of procedures and data; these two parts constitute a computer system resources, each program and the requirements of each user's requirements and use are different, and the allocation of appropriate control and coordination of computer resources is necessary.
Thus, we introduced an operating system: in a computer system, we focus on a software management function and control program execution function, called an operating system.
Ø Features of the operating system
1. Concurrent: There are several running programs in the computer system, from macro look, these programs are simultaneously advanced. Note that the difference between parallelism and concurrency these two concepts: Parallelism means that two or more events occur at the same time (micro concept), and concurrency refers to the interval between two or more events at the same time. (Macro concept).
2. Shareability: Operating System Program and Various Resources in Multiple User Programs Shared Systems: Central Processors, Internal and Outer Memory, External Equipment, etc. Two forms shared: mutual exclusion and simultaneous sharing.
3. Randomity: The operation of the operating system is running in a random environment. The meaning of this random environment is that the operating system is not possible to make any prior assumptions for the behavior of the running procedure and hardware devices.
Ø Different views on the nature of the operating system
Due to different views of the nature of the operating system, it will affect the design idea of the operating system. Several views on the operating system are as follows:
1. The software's point of view, learning and research in software in software, but pay attention to it has a special structure that is not available in general application software.
2. The viewpoint of resource management, the operating system is to be responsible for users and system programs more efficient use and coordinate the resources of computer systems (hardware and software resources).
3. The process of the process, can be simply considered that the process is a program running, each process is completed, which can be a system task, or a job task submitted by the user. According to this view, mainly focus on parallel work of each part of the analysis system, and process and manage tasks with each other.
4. The viewpoint of the virtual device, expands the original computer (bare metal) with the support of the operating system to a functional computer system, and we call this computer system as a virtual computer. All functions of the operating system, including system call / command / job control language, etc., collectively referred to as operating system virtualists. The operating system can be decomposed into several levels, each hierarchical function, which constitutes a virtual machine and supports the upper layer. Expand the entire operating system virtual machine by expanding and finally completing the entire operating system virtual device.
5. The service provider's point of view, the operating system provides a range of functions and convenient working environments for user services, so the operating system can be regarded as a service provider.
Ø Classification of operating systems
1. Batch operating system
Basic work mode: Users hand over the system operator, after the system operator receives the job, does not immediately enter the job
Computer, but after receiving a certain number of user homework, constitute a batch of jobs, then input this batch of jobs into the computer
Batch.
Early batch monitoring procedures do not have concurrent functions, in order to improve hardware resource utilization, the multi-digital batch processing system that realizes truly concurrent mechanisms is mainly achieved by spooling technology: that is, multiple jobs at the same time, host Multiple jobs can be handled simultaneously with alternating ways.
2. Minute system
It is developed to make up for the shortcomings of interactive fast services to make up for batch methods.
Basic work mode: A computer host is connected to several terminals, each terminal can be used by a user, and the user proposes a command request through the terminal to the system, after accepting the user command, using the time slice rotation to handle the service request, And display the result to the user over the terminal by interactive mode. The user issues the next interactive command based on the processing result sent back to the system.
The time-time operating system has a multi-channel, interactive, exclusive, and timely characteristic.
A typical UNIX operating system combines the characteristics of the scheduled system and batch system.
In a general-purpose operating system, the principle of processing of time-time and batch is: time-time priority, after the batch is behind. And generally refer to the system's timing and batch operation states as the front desk and the background, the front desk is mainly processed from the terminal user, interactive, relatively small and needs timely processing; the background job mainly handles longer To call other external devices, large-scale homework is not required to intervene, and do not require immediate processing.
4. Real-time operating system (RTOS: REAL TIME OPERATING SYSTEM)
Within a strict time, the system has a high reliability.
There are two main categories: hard real-time operating systems: hard real-time systems and soft real-time systems. Hard real-time systems have extremely strict requirements for time in event processing, while soft real-time systems are only required for a certain period of time in event processing.
5. Personal Computer Operating System)
Mainly for personal use, in a single user service, use the graphical interface of human machine interaction, interface friendship, easy to use, users do not need specialized knowledge, can also manipulate the system.
5. Network operating system
Based on computer networks, software is designed and developed by network architectural protocol standards over a variety of computer operating systems, including network management, general, security, resource sharing, and various network applications.
6. Distributed operating system
A large number of computers are connected together through the network to achieve extremely high calculation capabilities and extensive data sharing.
Like the network operating system, it is equally based on a computer network, but different from the network operating system is that each computer connected on the network adopts a unified operating system, and the distributed operating system dilutes the location of the accessed resource, that is, the concept of the network. The application layer is diluted, and the network operating system has the location and type of the resource must be displayed in the network operating system.
============================================================================================================================================================================================================= === Learning experience
The above is simply a summary of the function, characteristics of the operating system, so that I seem to be a bit clear about the operating system, isn't it the software for organizing computer system resources? Ok, the operating system is indeed software, but don't focus it with the usual application software. Different understandings of the operating system have produced the difference in operating system design ideas. The above has been very clear.
Let's take a look at the Windows2000 Personal Computer operating system (with the functionality of the distributed operating system), which is not bad for resource management, process schedules, and virtual devices.
Further examine the layering of the Windows2000 operating system, I will also draw: User interface, application, job management, file management, input output (I / O) management, process communication, storage management, processor management, to final Hardware device operation.
The Windows2000 operating system is interacting with the user program, such as you open a Word handler, what do you think of the system? At the beginning, the system needs to distribute the Word handler to store resources, and then the process is managed, and there is also the result of the result of the completion to output to a variety of external devices, know that our Word handler may crash at any time. The system also needs to have strong fault tolerance and stability, and it is possible to avoid the unstable application of the application, and the Windows2000 operating system provides the corresponding solutions for the above problems due to the instability of the application.
