Main functions of the Operating System

The main task of the operating system is to provide a good environment for multi-program operation to ensure that multiple programs can run in an orderly and efficient manner, and can maximize the utilization of various resources in the system and facilitate the use of users. To implement the above tasks, the operating system should have the following functions: processor management, memory management, device management and file management. To make it easier for you to use the operating system, you must also provide convenient user interfaces. In addition, because today's networks are widely used, more and more computer access networks are available. In order to facilitate computer networking, network-oriented services are added to the OS.

Processor management function: in traditional multi-channel programs, processing and allocation and operation are based on the progress. Therefore, management of the processing can be attributed to management of the process; in the OS where threads are introduced, thread management is also included. The main function room of processor management is to create and cancel the process (thread), coordinate the operation of various processes (threads), and exchange information between Real-Time Processes (threads, and process and assign it to the Progress (thread) according to certain algorithms ).
Process control: creates, revokes, and controls the process's zookeeper conversion during running, creates and revokes threads for the Process
Progress synchronization:
Process mutex
Progress synchronization mode
Progress communication:
Scheduling:
Progress Scheduling
Job Scheduling
Memory Management function: provides a good environment for multi-program operation, which facilitates the use of memory, improves the memory utilization and logically expands the memory.
Memory Allocation
Memory Allocation Data Structure
Memory Allocation Function
Memory reclaim Function
Memory Protection
Address ing
Memory expansion:
It is used to implement the following functions:
Request Transfer Function
Replacement
Device management function: complete the I/O requests submitted by the user; allocate the required I/O devices to the user; improves the utilization of CPU and I/O devices, and increases the I/O speed.
Buffer Management
Device allocation
Device processing (Device Driver): the basic task is to realize the communication between the CPU and the device controller,
Virtual Device
File Management
File storage space management
Directory management
File read/write management and protection

Interface between operating system and user
User Interface
Online User Interface

Offline User Interface (batch processing user interface ): this interface is composed of a group of Job control languages (jcl = a language that is provided to batch job users to delegate the system to control the required functions for implementation. The user uses jcl to write the control and intervention required for the job in advance in the job manual. The

Graphical user interface:

Program Interface: this interface is set for the user program to access system resources during execution. It is the only way for the user program to obtain the operating system service. It is composed of a group of system calls. Each system call is a subroutine that can complete specific functions. Early system calls were provided in assembly languages. system calls can be directly used only in programs written in assembly languages. However, in advanced languages and C languages, the database functions that correspond to system calls are often provided, so that the application can use the system call by calling the corresponding database functions. However, in the operating systems launched in recent years, such as UNIX and OS/2, system calls have been written in C language and provided in the form of functions, therefore, system calls can be directly used in programs compiled in C language.