The emergence, use, and development of the operating system (Operating System, OS for short) is a major advancement in computer software in the past forty years. Although the operating system does not yet have a strict definition, it is generally believed that the operating system is used to manage system resources, control program execution, improve the man-machine interface, provide various services, rationally organize computer workflows, and provide a good operating environment for users to effectively use computers. A system software.
With the development of computers today, from personal computers to supercomputers, without exception, they are equipped with one or more operating systems. The operating system has become an inseparable and important part of modern computer systems. It establishes various application environments for people. Laid an important foundation. The main goals of configuring the operating system can be summarized as follows: 1. Facilitate user use. The OS facilitates user use by providing a friendly interface between the user and the computer. 2. Expand machine functions. OS expands machine functions by expanding and transforming hardware facilities and providing new services. 3. Manage system resources. OS effectively manages all hardware and software resources in the system to make them fully utilized. 4. Improve system efficiency. OS reasonably organizes the working process of the computer to improve system performance and system efficiency. 5. Build an open environment. The OS is designed and constructed in accordance with relevant international standards to create an open environment. Its meaning mainly refers to: following relevant international standards (such as open communication standards, open user interface standards, open thread library standards, etc.); supporting the scalability and extensibility of the architecture; supporting applications on different platforms Portability and interoperability.
The computer system includes two components: hardware and software. Hardware is the material basis for all software operations. Software can give full play to hardware potential and expand hardware functions to complete various system and application tasks. The two promote each other, complement each other, and are indispensable. Each layer has a set of functions and provides corresponding interfaces. The interface hides the implementation details within the layer and provides usage conventions outside the layer. The hardware layer provides basic computing resources, including processors, registers, memory, and various I/O facilities and equipment. These facilities and equipment constitute the hardware of the computer system, which can receive and store information according to the needs of users , Data processing and output calculation results are the basis of the operating system and software. The operating system layer is usually the software layer closest to the hardware. It expands and transforms computer hardware for the first time. It mainly completes the scheduling and allocation of resources, the access and protection of information, and the coordination and control of concurrent activities. The operating system is the basis for the operation of other software at the upper level, and provides strong support for the designers of system programs such as compilers and database management systems. The working foundation of the system program layer is established on the machine modified and expanded by the operating system. By using the extended instruction set provided by the operating system, various language processing programs, database management systems and other system programs can be easily implemented. In addition, a wide variety of utility programs are provided, such as link assembly programs, library management programs, diagnostic troubleshooting programs, classification/combination programs, etc., for users to use. The application layer solves user-specific or different application needs. Application developers use programming languages to express application problems and develop various applications, which is fast and convenient. The end user interacts with the computer system through the application to solve his application problems.
The role and function of the operating system The role of the operating system in a computer system can be understood from three aspects: the operating system is the interface between the user and the computer hardware. The operating system provides users with a virtual machine (Virtual Machine). The operating system is the resource manager of the computer system.
The main characteristics of the operating system: 1. Concurrence (concurrence) 2. Sharing (sharing) 3. Asynchrony (asynchronism) 4. Virtual (virtual)
The evolution of operating systems
1. Serial processing system
In the early computers, from the late 1940s to the mid-1950s, programmers had direct contact with the hardware, and there was no operating system at all. The computer runs on a console that integrates indicators, various switches, some input devices, and a printer. The program written in machine code is loaded by the input device and the card reader. When the program is suspended due to an error, the error position is displayed by the indicator light. The programmer can find the cause of the error by checking the registers and main memory. If the program is executed normally, the result will be output to the printer.
2. Simple batch processing system
Early computers were very expensive, so it was important to make the most of them. The time effort caused by the early computer's on-board arrangement and bottom-up time is unacceptable. In order to improve the above situation, the concept of batch processing system was created. The first batch processing system was produced in the mid-1950s, developed by General Motors, and used on the IBM 701 computer. This concept was later improved by IBM's customers and applied in IBM 704. By the early 1960s, some owners developed batch processing systems on their own. IBSYS, the operating system configured by IBM for 7090/7094 computers, was particularly famous for its extensive influence on other systems. The central idea of the simple batch processing system is that by applying a software called a monitor, the user does not need to directly touch the machine, but first submits the job to the computer controller through the card sail and paper tape machine, and the monitor will The jobs are organized together to form a batch of jobs, and then the entire batch of jobs is put on the input device managed by the monitor. Whenever the job is executed and returned to the monitor, the monitor has automatically loaded the next job.
3. Multi-program batch processing system
4. Time-sharing system
Using multi-program design technology, batch processing of jobs can be efficiently performed. However, for many jobs, such as transaction processing, it is necessary to provide a direct interaction mode between the user and the computer.
5. Real-time system
Although the multi-pass batch processing system and time-sharing system have been able to obtain satisfactory resource utilization and response time, they still cannot meet the needs of real-time control and real-time information processing, such as missile guidance systems, aircraft ticketing systems, Information retrieval systems, etc., which gave rise to real-time systems.
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