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Basic features of operating system
The operating system mainly has three basic operating systems: multi-channel batch processing system, time-sharing system and real-time system. The batch processing system has high resource utilization and system throughput. The time-sharing system can obtain timely response, and the real-time system has real-time characteristics. , Their common basic characteristics are concurrency, sharing, virtual and asynchronous.
Concurrent
The feature that the programs in the system can be executed concurrently enables the OS to effectively provide resource utilization in the system and increase the throughput of the system.
Parallel and concurrency
Parallelism and concurrency are two different concepts. Parallelism means that two or more events happen at the same time, and concurrency means that two or more events happen in the same time interval.
shared
The meaning of sharing under normal circumstances is not exactly the same as that under operating system environment.
Mutually Exclusive Sharing
Although some resources in the system (such as printers) can be provided to multiple processes (threads), it should be stipulated that only one process can access the resource within a period of time. For this reason, a mechanism should be established in the system to ensure mutual exclusive access to such resources by multiple processes.
Simultaneous access
There is another type of resource in the system that allows multiple processes to access them "simultaneously" within a period of time. The "simultaneous" here is in the macroscopic sense in a single-processor environment, while in the microscopic view, these processes access the resource alternately. A typical resource that can be "simultaneously" accessed by multiple processes is a disk device. Some files written with reentrant codes can also be shared "simultaneously", that is, allowing several users to access the file at the same time.
virtual
Time division multiplexing
(1) Virtual processor technology.
(2) Virtual device technology.
Space Division Multiplexing Technology
Frequency division multiplexing technology divides a channel with a relatively wide frequency range into multiple channels with a narrow frequency range (called frequency bands), and any one of the frequency bands is only for a pair of users to talk. Frequency division multiplexing technology can divide a physical channel into thousands of voice channels. Frequency division multiplexing technology can improve channel utilization. Space division multiplexing technology is used for the management of storage space to improve the utilization of storage space.
asynchronous
In a multi-program environment, the system allows multiple processes to execute concurrently. In a single processor environment, only one process is allowed to execute at a time, and the remaining processes can only wait. When the executing process makes a certain resource request, such as a print request, and the printer is printing for other processes at this time, because the printer is a critical resource, the executing process must wait and release the processor until the printer is idle. And when the processor is obtained again, the process can continue. Due to the limitation of resources and other factors, the execution of the process is usually impossible to "all in one go", but to run in a "stop and go" manner.
The purpose of introducing OS:
to provide a good operating environment for the operation of multi-programs, to ensure that multi-programs can run in an orderly and efficient manner, to maximize the utilization of various resources in the system, and to facilitate the use of users.
exercise
1. What is an operating system?
The operating system is the first layer of software configured on the 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.
2. What aspects of the role of the operating system can be expressed?
(1) The OS serves as the interface between the user and the computer hardware system.
(2) OS as the manager of computer system resources.
(3) The OS realizes the abstraction of computer resources.
3. What are the main goals of the operating system?
The main goals of configuring an operating system on a computer system are: convenience, effectiveness, scalability and openness. Among them, convenience and effectiveness are the two most important goals when designing os.
4. What are the goals of batch system, time-sharing system, and real-time system?
The goals of the batch processing system:
(1) Short average turnaround time
(2) High system throughput
(3) High processor utilization
The goals of the time-sharing system are:
(1) Fast response time
(2) Balanced
real-time system goals Yes:
(1) Guarantee of deadline
(2) Predictability
5. How does the OS realize the abstraction of computer resources?
OS first covers a layer of I/O device management software on the bare metal, which realizes the first level of abstraction of computer hardware operations;
and then covers the file management software on the first layer of software, which realizes the second level of abstraction of hardware resource operations . OS enhances system functions by installing multi-layer system software on computer hardware, hides the details of hardware operation, and realizes the abstraction of computer resources together by them.
6. There are several main driving forces to promote the development of operating systems. What are the differences?
The main power comes from five aspects:
(1) Continuously improve the utilization rate of computer resources.
(2) Convenient for users.
(3) Continuous updating of devices.
(4) The continuous development of computer architecture.
(5) Constantly put forward new application requirements.
7. The problem that multi-pass batch processing system needs to solve?
(1) The problem of processor contention.
(2) Memory allocation and protection issues.
(3) I/O device allocation problem.
(4) File organization and management issues.
(5) Job management issues.
(6) The problem of the interface between the user and the system.
8. What are the main driving forces and advantages and disadvantages of the formation and development of multi-pass batch processing systems?
The main driving force to promote the formation and development of multi-pass batch processing systems is to improve resource utilization and system throughput. Advantages and disadvantages:
(1) High resource utilization. (2) The system throughput is large.
(3) Long average turnaround time. (4) No interactive ability.
9. What are hard real-time tasks and soft real-time tasks? And try to illustrate.
A hard real-time task means that the system must meet the deadline of the task, otherwise unpredictable results may occur. Examples: industrial and weapon control, etc.
The soft real-time task means that its deadline is not strict, and the deadline of the task is occasionally missed, which has little impact on the system. Example: Information query system.
10. What are the major features of OS? What are its most basic characteristics?
The four basic characteristics of concurrency, sharing, virtuality and asynchrony, the most basic characteristic is concurrency.
11. What are the advantages of a microkernel operating system? Why can it have these advantages?
(1) Improve the scalability of the system. (2) Enhance the reliability of the system.
(3) Strong portability. (4) Provides support for distributed systems.
(5) Incorporating object-oriented technology.
12. From which four aspects the microkernel operating system is described.
(1) A sufficiently small kernel. (2) Based on the client/server model.
(3) Principle of separation of application mechanism and strategy. (4) Using object-oriented technology.
13. What are the main functions of file management? What is its main task?
The main functions of file management: file storage space management, directory management, file read/write management and protection.
The main task of file management: manage user files and system files to facilitate user use and ensure file security.
14. What are the main functions of memory management? What are their main tasks?
The main functions of memory management are: memory allocation, memory protection, address mapping and memory expansion.
(1) Memory allocation: allocate memory for each program.
(2) Memory protection: to ensure that each user program runs in its own memory space and does not interfere with each other.
(3) Address mapping: Convert the logical address of the address space into the memory space and the corresponding physical address.
(4) Memory expansion: used to realize the request call function, replacement function, etc.