Features and differences of the current popular operating systems

At present, there are four mainstream operating systems: Windows operating system, Linux operating system, Unix operating system and Mac operating system.

An operating system, or OS for short, is a computer program that manages the hardware and software resources of a computer. The operating system handles basic tasks such as managing and configuring memory, prioritizing the supply and demand of system resources, controlling input and output devices, operating the network, and managing the file system. The operating system also provides an interface that allows the user to interact with the system.

Key features of the operating system:

1. Process management, its work is mainly process scheduling, in the case of a single user and a single task, the processor is only exclusive to a task of a user, and the work of process management is very simple. However, in the case of multiple programs or multiple users, when organizing multiple jobs or tasks, it is necessary to solve the problems of scheduling, allocation, and optimization of the processor.

2. Storage management is divided into several functions: storage allocation, storage sharing, storage protection, and storage expansion.

3. Device management has the following functions: device allocation, device transmission control, and device independence.

4. File management: file storage space management, directory management, file operation management, and file protection.

5. Job management is responsible for handling any requirements submitted by users.

Concurrency, sharing, virtuality, asynchronicity.

Concurrency: Refers to the occurrence of two or more events in the same time interval, which occur simultaneously at the macro level but alternately at the micro level. Parallel:

Refers to two or more events occurring at the same time. The concurrency of the operating system: refers to the "concurrent" running of multiple programs in a computer system, which are running simultaneously at the macro level and alternately at the micro level.

Operating system and program concurrency are born together. Our computer's CPU has single-core, dual-core, quad-core, octa-core! A single-core CPU can only run one program at a time, and each program can only be executed concurrently (using the CPU alternately)!

A multi-core CPU can execute multiple programs at the same time, and multiple programs can be executed in parallel (running at the same time). Sharing: Resource sharing, which means that the resources in the system can be used at the same time in multiple concurrently executing processes in memory.

By "simultaneous", we tend to be at the macro level, while at the micro level, these processes may alternately access resources (i.e., time-sharing). There are two ways to share resources: mutually exclusive sharing mode and simultaneous sharing mode.

Mutually exclusive sharing mode: Some resources in the system can be used by multiple processes, but only one process is allowed to access the resources in a time period. Simultaneous sharing method:

Some resources in the system allow them to be accessed "simultaneously" by multiple processes for a period of time. Concurrency and sharing are mutually existent. Virtual:

It refers to the transformation of a physical entity into several logical counterparts, the physical entity (the former) is actually there, and the logical counterpart (the latter) is felt by the user. Asynchronous: In a multi-program environment, multiple programs are allowed to be executed concurrently, but due to limited resources, the execution of the process is not managed to the end, but to move forward at an unpredictable speed of stop-and-go, which is the asynchronous nature of the process!

Only if the system has concurrency, it can lead to asynchronicity, and without concurrency and sharing, there is no virtual and asynchronous.

Operating system (operationsystem, OS) refers to the control and management of the hardware and software resources of the entire computer system, and the reasonable organization and scheduling of computer work and resource allocation, so as to provide users and other software with convenient interfaces and environments, it is the most basic system software in the computer system. Users can interact directly with the operating system, but in most cases through an application. Hardware refers to resources such as CPU, memory, and hard disks.

Brand model: Lenovo Legion Y9000P

System: Windows 11

The main characteristics of the operating system: concurrency, sharing, asynchronicity, virtuality.

1. Concurrency: refers to the occurrence of two or more events in the same time interval. The concurrency of an operating system refers to the fact that there are multiple running programs in a computer system at the same time, so it should have the ability to process and schedule multiple programs to execute at the same time.

Concurrency needs to be supported by hardware, such as multi-pipeline or multi-processor hardware environments.

2. Sharing: It means that the resources in the system (hardware resources and information resources) can be used by multiple concurrently executed programs, rather than being monopolized by one of them. There are two ways to share resources: mutually exclusive access and simultaneous access.

3. Asynchronousness: In a multi-program environment, multiple programs are allowed to execute concurrently, but due to limited resources, the execution of the process is not consistent to the end. It's about stopping, moving forward at an unpredictable pace, and that's the asynchronous nature of the process.

Asynchronousity causes the operating system to run in a random environment, which can lead to time-related errors in the process. However, as long as the operating environment is the same, the operating system must guarantee that the same result will be obtained by running the program multiple times.

4. Virtuality: Virtuality is a management technology that turns a physical entity into a logical number of counterparts, or a physical entity into a logical counterpart. The purpose of adopting virtual technology is to provide users with an easy-to-use, convenient and efficient operating environment.

The characteristics of the operating system are divided into four characteristics: concurrent, shared, virtual, and asynchronous.

1. Concurrency. Concurrency is when two or more events occur in the same time interval. These things happen simultaneously at the macro level, but alternately at the micro level.

The concurrency of an operating system refers to the fact that multiple programs are running "at the same time" in a computer system, which are running simultaneously at the macro level and alternately at the micro level.

For concurrency and parallelism, we need to pay attention to:

A single-core CPU can only execute one program at the same time, and each program can only be executed concurrently, while a multi-core CPU can execute multiple programs at the same time, so multiple programs can be executed in parallel, but concurrency is still essential for a multi-core CPU.

2. Sharing. Sharing means that the resources in the system can be used by multiple concurrently executing processes in memory, and the way of resource sharing is divided into the following two ways:

Let's take a real-life example:

Simultaneous sharing method: Use QQ to send file A, and use WeChat to send file B at the same time. At a macro level, both sides are reading and sending files at the same time, indicating that both processes are accessing the hard disk resources and reading data from them. Microscopically, the hard disk is accessed alternately.

For concurrency and sharing:

If concurrency is lost, only one program is running in the system, and shareability loses its relevance.

In summary, concurrency and sharing are mutually existent.

3. Virtual. Virtual == refers to the transformation of a physical object into a number of logical counterparts. The physical object (the former) is physically present, while the logical counterpart (the latter) is felt by the user. == Virtual technology can be divided into the following categories:

Fourth, asynchronous. Asynchronous means that in a multi-program environment, multiple programs are allowed to execute concurrently, but due to limited resources, the execution of the process is not consistent, but stop-and-go, moving forward at an unpredictable speed, which is the asynchronous nature of the process.

The basic characteristics of the operating system are as follows:

1. Concurrency:

It is the presence of multiple programs at the same time in a computer system, and from a macro point of view, these programs are advancing at the same time. On a single CPU, these concurrently executed programs are run alternately on the CPU.

Program concurrency is manifested in two ways: Concurrent execution between user programs and user programs. Concurrency between user programs and operating system programs.

2. Sharing:

Resource sharing is when an operating system program and multiple user programs share resources in a system.

3. Randomness:

Randomness means that the operating system is running in a random environment, and a device may make an interrupt request to the processor at any time, and the system has no way of knowing what the running program will do and when.

4. Virtual

It refers to the technological transformation of a physical entity into several logical counterparts. In the operating system, the implementation of virtualization is mainly through the use of time-sharing. Obviously, if n is the number of virtual logical devices corresponding to a physical device, the speed of the virtual device must be 1 n of the speed of the physical device.

5. Asynchronicity: i.e., uncertainty. Multiple runs of the same program and data may yield different results; There is also uncertainty about the running time and sequence of the program; It is difficult for external input requests and operational failures to occur at a time. These are all manifestations of uncertainty.