Operating System Overview-Operating System (OS) is the most important System Software

1. Operating System Functions

1 ),From the perspective of computer system composition-the operating system isSystem Software

Computer system composition:

• Software: application software, system software (operating system, language processing system and common routine service programs)
• Hardware: input/output (I/O) device, memory (memory), central processor (CPU)
• Firmware (expansion): to improve the performance of the system, the software that is closely related to the hardware in the operating system is converted into hardware through microprogram design technology, which is usually referred to as curing.The hardware of software functions is called firmware..

2 ),From the perspective of resource management programs-the operating system isSystem Resource Manager
(Operating system as a Resource Manager)

An operating system is a system resource management program. It is used to control and manage hardware and software resources of a computer system, as shown in the following table:

Computer System Resources		Operating System Module
Software		File System
Hardware	I/O device	Device management
Hardware	Memory	Memory Management
Hardware	Processor	Processor (process) Management

3 ),From the perspective of software hierarchy and machine expansion-the operating system isExpand bare metal first-level system software

Bare metal: A computer composed of hardware is called a bare metal. A bare metal can only execute the machine code language and is unavailable to general users.

 

4 ),From the perspective of service users-the operating system isInterface between user and bare metal

The system provides two types of interfaces:

• Job-level interface: it provides a setKeyboard commandsAllows you to organize and control the running of your jobs.
• Program-level interface: it provides a setSystem CallThat is, the function of a module in the OS, which can be called by user programs and other programs.

5 ),From the process point of view-the operating system is composedSeveral processes that can be executed concurrentlyAnd a core component that controls and coordinates processes.

2. Operating System definition

The operating system is a groupValidControl and Manage hardware and software resources of computer systems,ReasonableOrganize computer workflows andConvenientA collection of user programs.

• Valid (efficiency ):System efficiency and resource utilization (for example, whether the CPU utilization is sufficient, whether the memory and external devices are busy)
• Reasonable:Fairness or not. If unfair, a "deadlock" or "Hunger" will occur"
• Convenience ):User Interface

 

3. Operating System history

1) No operating system exists in the 1949th generation (not in December-early September)

In this caseProgrammerUse manuallyComputer Hardware System.

2) The first generation (not in mid-December 1950s and not in December 1950s) Preliminary single-channel Batch Processing System

It is designed to reduce manual operation time and job conversion time to improve CPU utilization.AutomaticBatch Process jobs. This isPreliminary single-channel batch processing system.

3) Multi-Channel Program Design Sharing System in the second generation (from the beginning of 1960s to the middle of 1960s)

This generation of operating systems includes multi-channel batch processing systems and interactiveTime-sharing systemAnd improves the instantaneous response time.Real-Time System.

4) third-generation (mid-December 1960s-mid December 1970s) Multi-Mode System

This generation of computer systems is a general system, and this generation of operating systems is a multi-mode system, that is, a systemBatch Processing, time-based processing, real-time processing, and multiple Processing.

5), the fourth generation (mid-December 1970s-) network operating system and Distributed Operating System

The network operating system is implemented on the computer network.Information exchange, resource sharing and interoperability.

Distributed Operating SystemDistributed systems in different regions are interconnected into a system with overall functionsAnd a task can be run on each system in a distributed manner.

 

Operating system development stage:

• FirstMainframe EraAs a part of hardware, the operating system is designed by the hardware developer;
• The second isHuman computers or small hostsSoftware and Hardware go hand in hand, during which there are two phases: Command Line-based DOS Operating System; AndWindows Operating System Based on window GUI.
• The third historical stage:Web Age. Microsoft. NET TechnologyWith Sun'sSun ONE Platform.

4. Computer Hardware System Overview

1 ),Computer hardwareSystem Structure

• Large, medium, and small computer hardware organization: memory-centric, CPU and various channels are connected to memory

• Typical organization of a microcomputer: a microcomputer is a computer system consisting of a bus, a central processor (CPU), a memory, and an I/O device (including external disks and tapes) all are attached to the bus.

2 ),Hardware basics of Modern Operating Systems

Hardware supporting parallel operations-channels and interruptions

To improve the utilization of computer resources, modern computer systems adopt multi-channel programming technology.Primary StorageAllows you to store jobs of multiple users. The computer system hardware supports parallel job operations, so that multiple jobs are running at the same time and share system resources.In modern batch processing systems, hardware that supports parallel operations is channel and interrupt.

• ChannelIt can be used in parallel with the CPUControl Input/output device Data Transmission. When the CPU needs to input data, as long as the command is sent to the channel to complete, the channel can perform I/O operations and CPU operations in parallelAsynchronousAfter the channel completes the I/O operation, it reports the I/O completed to the CPU in an interrupted manner.
• InterruptedIt refers to the CPU-to-SystemAsynchronous eventsAsynchronous events referRandom events without a certain time series relationship. The meaning of interruption is that when these asynchronous events occur, the processor is interrupted to execute the current program, and then the asynchronous event is processed, that is, the interrupt handler of the event is executed, after the processing is complete, switch to the central breakpoint of the original program for execution.
• The pause point of the program being executed when the interruption occurs is calledInterrupt breakpointThe process in which the processor suspends the current program to handle the interruption is calledInterrupt responseThe execution of the original program is calledInterrupt return.
• Interruption can be divided into two categories: hardware interruption and software interruption. The interrupt request level table is as follows: