1)The purpose of operating system:

    Operating System (OS) is the first layer of software configured on computer hardware and is the first expansion of the hardware

system. Its main function is to manage these devices, improve their utilization and system throughput, and provide a simple

interface for users and applications, which is convenient for users to use. OS is the most basic and important system software in

modern computer systems, while other system software such as compilers, database management systems, and a large number of

application software directly rely on the support of the operating system to obtain the services it provides .

    The goal of the operating system is related to the application environment. For example, the OS used in the query system. Hope

to provide good human-computer interaction: For the OS used in industrial control, weapon control, and multimedia

environments, it is required to have real-time performance: For the OS configured on the microcomputer, it is even more What is

important is the convenience of its use.

    The main goals of configuring an operating system on a computer system are: convenience, effectiveness, scalability and

openness.

1. Convenience

    A computer system without an OS is extremely difficult to use. If users want to run their own programs directly on computer

hardware (bare metal), they must write programs in machine language. But if the OS is configured on the computer hardware, the

system can use compile commands to translate programs written by users in high-level languages ​​into machine code, or directly

manipulate the computer system through various commands provided by the OS, which greatly facilitates users and makes The

computer becomes easy to learn and use.

2. Effectiveness

    The first meaning of effectiveness is to improve the utilization of system resources. In the early computer systems that were not

configured with OS, processors, I/O devices, etc. were often idle, and various resources could not be fully utilized. Therefore, at

that time, improving the utilization of system resources was the main driving force for the development of OS. Another meaning of

effectiveness is to improve the throughput of the system. The OS can speed up the running of the program and shorten the

running cycle of the program by rationally organizing the work flow of the computer, thereby improving the throughput of the

system.

3. Scalability

    In order to meet the requirements of computer hardware, architecture and computer application development, the OS must

have good scalability. The scalability is very closely related to the structure of the OS, which promotes the continuous development

of the OS structure: from the early unstructured to the modular structure, and then to the hierarchical structure, the OS has been

widely used in recent years A micro-kernel structure is adopted. The micro-kernel structure can easily add new functions and

modules, as well as modify the original functions and modules, and has good scalability.

4. Openness

    With the increasing popularity of computer applications, the issue of compatibility of computer hardware and software has been

brought up on the agenda. Countries around the world have accordingly formulated a series of software and hardware standards,

so that the software and hardware produced by different manufacturers in accordance with the standards can be compatible with

each other within their own countries. This undoubtedly brings great convenience to users and paves the way for product

promotion and application. In recent years, with the rapid development of the Internet, the application environment of the

computer OS has changed from a stand-alone environment to a network environment, and its application environment must be

more open, which in turn puts forward higher requirements for the openness of the OS.

2)The functions of the operating system

    The function of the operating system in a computer system can be analyzed and discussed from many different perspectives

such as users, resource management, and resource abstraction.

1. OS as the interface between the user and the computer hardware system

    The meaning of the OS as the interface between the user and the computer hardware system is: OS is between the user and the

computer hardware system, and the user uses the computer system through the OS. In other words, users can conveniently,

quickly and reliably manipulate computer hardware and run their own programs with the help of the OS. The user can use the

computer in three ways, namely through the command mode, the system call mode and the icon window mode to realize the

communication with the operating system and obtain its services.

2. OS as the manager of computer system resources

    In a computer system, it usually contains a variety of hardware and software resources. In summary, these resources can be

divided into four categories: processors, memories, I/O devices, and files (data and programs). Correspondingly, the main

function of the OS is to effectively manage these four types of resources. Processor management is used to allocate and control

processors; memory management is mainly responsible for the allocation and recovery of memory; I/O device management is

responsible for the allocation (recycling) and manipulation of I/O devices; file management is used to implement file management

Access, share and protect. It can be seen that OS is indeed the manager of computer system resources.

3. The OS realizes the abstraction of computer resources

    For a completely software-free computer system (i.e. class machine), because it only provides the user with a hardware interface

(physical interface), therefore, the user must have a full understanding of the implementation details of the physical interface,

which leads to the Physical machines are difficult to use widely. In order to facilitate users to use I/O devices, people overlay a

layer of I/O device management software on the bare metal, which implements the details of the I/O device operation and

abstracts the I/O device upwards as -A group of data structures and a group of I/O operation commands, such as read and write

commands, so that users can use these data structures and operation commands to input or output data without worrying about

how I/O is implemented. At this time, the machine the user sees is a machine with stronger functions and more convenient to use

than bare metal. In other words, the I/O software laid on the bare metal hides the specific details of the I/O device and provides a

set of abstract I/O devices upward. It can be seen that the OS is a collection of multi-layer software laid on the computer hardware.

They not only enhance the kinetic energy of the system, but also hide the specific details of the hardware operation, and realize the

multi-level abstract model of the computer hardware operation. It is worth noting that not only can a hardware resource be

abstracted at the bottom level, but also the abstracted model at the bottom of the resource can be abstracted again at the high level

to become a higher-level abstract model. As the abstraction level increases, the functions provided by the abstract interface are

stronger, and the more convenient for users to use it.