# Basic knowledge of computer operating system

Basic knowledge of computer operating system

Computer development and classification

1. Manual stage
2. Batch stage
   1. Single-batch phase
   2. Road Batch multi-stage
3. Sharing operating system
4. Real-Time Operating System

Manual processing stage, the disadvantage is the low use of hardware, manual input and hardware processing speed mismatch.

Single-batch phase, the disadvantage is also a low processing hardware, each can only run one application.

Multi-channel batch stage, the advantage of memory can store multiple applications, hardware utilization out. The disadvantage is that after the program is running will not be able to intervene in the execution of the program, it will not be able to carry out human-computer interaction.

Phase-sharing operating system, the time division process referred cpu plurality of time slices allocated for a different, in response to different user inputs. High hardware utilization, capable of human-computer interaction. The disadvantage is that does not distinguish between priority of the task, we need to line up.

Real-time operating system, able to complete some urgent tasks within a certain time limit, without the need for time-slice queue. Which in turn are divided into hard real-time and soft real-time: missile launchers, unmanned is hard real-time operating system, and the booking system is the soft real-time operating system. The difference between them is a guarantee can be absolutely completed within the stipulated time, while the latter allows the occasional violation of the provisions of the time.

Operating System Interface Category

1. Command Interface

For example, such common bash, cmd command interpreter, etc., available to users of

2. program interface (system calls)

The user can not directly access program provided to, for example using network programming socket

3.GUI (graphical user interface)

​ Windows，MacOS

Operating System Features

1. Virtualization

   The actual hardware resource virtualization and as a service to provide top

2. Complicated by

And parallel difference is that, while running concurrently at the macro level, but at the micro level cpu each time there is only one program running.

1. shared

   Concurrent mutually dependent, i.e., the system for sharing resources among different programs, share is divided into the following two:

   1. Share the mutex

      Is the same resource at a time can have only one program can access additional program attempts will be blocked during this time way

   2. At the same time access method

      Instant access to resources at the same time, such as disk and sound

2. asynchronous

   In the multi-channel programming environment that allows concurrent execution of multiple programs, but due to limited resources, the implementation process is not always in the end, but stop and go, in order to move forward at an unpredictable rate, which is the asynchronous nature of the process.

   Asynchronous makes the operating system runs in a random environment, the process may lead to an error in a time-dependent. But as long as the same operating environment, the operating system must ensure that multiple processes running, all get the same results.