Python full stack day03 operating system--summary

first, the operating system

In order to realize the function, improve efficiency, fully and efficiently manage and optimize the use of computer hardware, user-friendly, the computer on the basis of its hardware installed a layer of software, and operating Systems. Operating system tasks are good and fast, convenient and quick to manage all devices.

The operating system will be cumbersome, all used to manipulate the hardware of the calling program to operate, and optimize the use of hardware this extremely tedious work, the total liberation of the user, improve the efficiency, users can write using the operating system to achieve indirect call hardware work software, There is no need to consider all the hardware operation details to take into account, efficient and fast implementation of the Function. At the same time, the operating system is hardware-protected, not user-changed, stable, large-scale software.

second, the location of the operating system

The operating system is located between the computer hardware and the application software, which is essentially a software. The operating system consists of the system kernel (which runs in the kernel state to manage the hardware resources) and the system call (which runs in the user state and calls the system call interface provided by the application hardware).

third, the function of the operating system

The operating system has two major functions,

first, simplify and beautify the function of calling hardware, the operating system through the hardware driver for the application call hardware to provide a corresponding system call interface, developers in the development of applications, it is not necessary to consider the hardware details, directly call the corresponding interface, running on the operating system, convenient and Efficient.

secondly, It is the orderly distribution of the disorderly competition operation request Management. When Multi-application multithreading runs on an operating system at the same time, these applications or threads may all need to be a certain hardware resource at the same time, in order to solve the problem that the competition between applications leads to the processing result disorder, the operating system will order these chaotic operations, multiplexing, ordered to complete the command.

Iv. History of operating system

1. First generation computer (1940-1955): vacuum tube and punch card

The first generation of computers, completely designed to replace human power with machinery, does not have an operating system concept, and all programs need to be written in purely mechanical languages. Both the handler and the CPU are executed one at a Time.

Use this kind of computer needs to use the appointment time, in its use process other people need to wait in line, although is the resource exclusive, the problem can be solved in time, but there are countless people behind for its normal use of this computer to do the maintenance Work. Time use is also a question to be questioned, some people operate fast, some slow operation, and some need to test a program and others need to test multiple programs. result in uneven time.

2. Second generation computer (1955-1965): transistor and batch processing system

In order to reduce time, to achieve batch processing and design of the second generation of computers, directly by the computer room, has its own batch processing operating system, while the operators and maintenance personnel have a clear division of labor, but to achieve the function also requires Human-machine Cooperation.

The computer collects the collected data into a large wave of input data, let the computer do sequential operations, batch processing, and then save the results into a large wave of data Output. This design not only causes the programmer to not be able to enjoy the computer resources, but also has the problem which cannot deal with the bug in Time. Affect the Efficiency.

Third generation computer (1965-1980): IC chip and multi-channel program design

The second generation of computers based on the addition of multi-channel technology design, eliminating the operation of the middleman, the computer processing data and output data functions linked Together. Multi-channel technology solves the problem of sequential scheduling of multiple programs on a shared resource by multiplexing. Resources are now multiplexed on time and Space. Although it is also a batch model, this computer provides a fast interactive mode that allows users to think that they are using exclusive Resources.

The third generation of computers in the use of the necessary hardware protection programs (memory between programs, hard disk isolation), the user data will not penetrate between the leakage, only widely popular.

Fourth generation computer (1980-present): pc

There are hardware support, an operating system, and a supercomputer that is composed of applications that can run on the operating System.

five, Multi-channel Technology

Multi-channel technology refers to the use of time multiplexing and spatial multiplexing, processing multiple users from multiple programs initiated multiple shared resources Requests.

Time multiplexing: When multiple programs are running on the same hardware, the operating system assigns the first program to be used, and when the processing or blocking occurs, The jump switches to another program, which in turn executes. How long the application is used on the hardware is determined by the operating System.

Spatial Multiplexing: When multiple applications use the same large resource, the system allocates a small, isolated resource to each of the programs, and multiple program resources exist simultaneously, invoking to save time and improve Efficiency. For example, a hard disk allocates different storage application space for multiple users, and these users isolate complementary access.

Python full stack day03 operating system--summary