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Is Unix the same as Linux? Many novices are not very clear about this. In order to help you solve this problem, the following editor will explain it in detail. People with this need can come and learn. I hope you can gain something.

Unix is not an operating system that appeared in the early 1970s. Unix can be used not only as a network operating system, but also as a stand-alone operating system. Linux is a set of UNIX-like operating system that is free to use and spread freely, which is mainly inspired by the ideas of Minix and Unix.

Unix function module

The operating system manages the hardware and software resources of the computer system in order to be used by users. Hardware resources generally refer to CPU (central processing unit), memory (memory and external memory), external devices and so on. Software resources refer to system programs and data, that is, operating systems, system utilities and application software, as well as user programs and data, which are stored in memory in the form of files. The operating system is organically linked by several functional modules and works harmoniously. These modules are: processor and process management module, storage management module, device management module, file system and user interface.

Processor and process management module

Because the processor (CPU) is the key resource in the computer, and the execution of the process is closely related to the CPU, the processor and process management module can be referred to as the process management module for short. We call job scheduling the task of determining which jobs will be transferred to memory to run and exit memory after completion of the run. How to control the transition between the three states of a job at run time is called process scheduling. Therefore, how to give full play to the utilization of resources, make the response time short, and minimize the time for each user's job to wait for execution is the principle of formulating the corresponding job scheduling algorithm and process scheduling algorithm. Only in different operating systems, there are different focuses on the above objectives, so the scheduling algorithm is also different.

Storage management module

Storage management is to manage the memory (including memory and out-of-memory) used by the job from the time it enters the ready state to the end of the run. The task of storage management module can be divided into three parts: storage allocation, address mapping and storage protection.

Storage allocation

A program compiles and links to a file called a memory image. This file describes the amount of memory required for the program to run, including the code and the address of the datazone. These addresses are called logical addresses and have the first address 0 as the reference address. Whenever a job calls into memory and enters the ready state, the storage management module calculates according to both the available memory space and the memory needed by the job, and allocates the corresponding memory space to the job.

Address mapping

Loading a job into memory means that a process will be created. The storage management module aligns the first address of the job's image file (zero) at the first address of the process in memory. The first or starting address of this process is the physical address in memory, called offset. The logical address of the image file plus the offset gives that the address values in memory are all physical addresses. Calculating the translation of logical addresses to physical addresses is called address mapping. All logical addresses in the image can be translated into physical addresses. [2]

Memory protection

Memory space is always shared by several processes, including the part of the operating system itself that resides in memory. The task of memory protection is to know which processes they belong to and which areas each process is entitled to access to the areas that have been divided into memory space. Whenever a process needs to access an address during execution, the storage management module checks to see if the process has access to the physical address. Typically, the area of each process in memory is a legitimate address that the process can access. Illegal access occurs if the accessed address falls outside the area of the process. Once illegal access is encountered, memory protection denies access and handles errors.

Equipment management module

External devices include file storage media, such as magnetic disks, magnetic tapes, optical discs, and other input and output devices, such as character terminals, graphics terminals, various printers, plotters, displays, etc., as well as dedicated input and output devices, such as data acquisition devices, image intake devices, audio input and output devices, etc.

The task of the device management module is to provide users with a convenient and unified interface, allocate these resources reasonably according to the application of the job to the device, and classify the devices according to the performance and function of the equipment. and then use different drivers to drive these devices to work, in order to improve the efficiency of the devices.

File system

File system can also be called information management module, or file management module, which is mainly responsible for the management of software resources. All software resources are stored in the storage medium in the form of files, and the information is transmitted in the computer in the unit of files. Therefore, a file is defined as a collection of related information elements. All files form a file system in the computer, although they have the same name as a management module of the operating system, but they are usually distinguishable because of their different situations and contexts.

User interface

User interface (user interface) is also called user interface. Users use the operating system through the user interface. A good user interface will make users feel the friendliness and convenience of the operating system. The user interface usually includes job control language, operation language and system call.

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