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MindMap Gallery Operating system introduction mind map

Operating system introduction mind map

This is a mind map about the introduction of operating systems. OS refers to the rational organization of hardware and software resources that control and manage the entire computer system, schedule the work and resource allocation of the computer, and then provide convenient interfaces and environments for users and other software. collection of programs. It is the most basic system software in the computer system.

Edited at 2023-12-01 15:57:29

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Operating system introduction mind map

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Outline

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OS Chapter 1
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operating system
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- 2
- 2
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Processes and Threads
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Computer System Overview
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Operating System
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operating system

Introduction

OS concept (definition)

OS refers to the hardware and software resources that control and manage the entire computer system. Reasonably organize and schedule computer work and resource allocation, A collection of programs that provides convenient interfaces and environments for users and other software. It is the most basic system software in the computer system.

operating system characteristics

Concurrency (most important, prerequisite for other features)

Two or more events occur within the same time interval

shared

The resources in the system can be used by multiple concurrently executing processes in memory. Resource sharing is sharing

Mutually exclusive sharing mode (shared use of camera equipment)

Simultaneous access mode (shared use of hard disk resources)

The most basic characteristics, the two are the conditions for the existence of each other

virtual

Transform a physical entity into several logical counterparts

time-sharing resources

asynchronous

The multiprogramming environment allows multiple programs to execute concurrently. Due to limited resources, the execution of the process is not consistent, but stop-and-go. It advances at an unpredictable speed.

Operating system goals

Convenience

effectiveness

Scalability

openness

Goals and functions The role of the operating system service provided

OS as the manager of computer system resources

Processor management

memory management

Device management

File management

OS serves as the interface between the user and the computer hardware system (Providing services to upper levels)

For ordinary users

GUI graphical user interface (which ultimately boils down to a program interface)

command interface

Online control method

Online command interface (interactive command interface) suitable for time-sharing or real-time systems

Offline control mode

Offline command interface (batch command interface) is suitable for batch processing systems

Software/programmer use

Program interface (system call == generalized instruction)

The user requests the OS to provide services by using system call commands in the program. Users can directly use system call commands in the program to make various service requests to the system.

For example, using external devices, performing operations on disk files, Apply to allocate and reclaim memory and various control requirements

OS used as an expansion machine Implement abstraction of computer resources

Extended Machine/Virtual Machine: Machine with software covered

development and classification

manual stage

shortcoming

User exclusive use of the entire machine

The CPU is waiting for manual operation and the CPU is not fully utilized.

Conflict between man and machine, conflict between CPU and I/O speed

Batch processing stage

Single-channel batch processing system (introduction of offline input and output technology)

Advantages: Alleviating the conflict between human and machine speeds

Disadvantages: Resource utilization is still low, high-speed CPU waits for low-speed I/O

Multi-channel batch processing system (multi-programming technology operating system begins to appear) Multi-programming (multi-channel, macro-parallel, micro-serial)

advantage

High resource utilization, multi-programming shares computer resources

System throughput is high, CPU and other resources stay "busy"

shortcoming

Long user response time and drone interaction capabilities

time-sharing OS

advantage

Provide human-computer interaction functions

shortcoming

Unable to prioritize urgent tasks

Real-time OS

Soft real-time system

Ability to accept occasional time violations without causing permanent damage

hard real-time system

An action must absolutely occur at a specified moment (or within a specified time range)

Pros: Ability to prioritize urgent tasks

Microcomputer operating system

Network OS

Distributed OS

PC OS

Operating environment

Operating mechanism

How the program works

High-level language programming——>Machine instructions

The process of program running is the process of CPU executing instructions.

two procedures

kernel program

app

Two types of instructions

Privileged instructions (such as I/O instructions, interrupt instructions, etc.)

unprivileged instructions

Access management instructions (the execution of the program is transferred from user mode to core mode)

Two processor states

Kernel state/core state/tube state

User mode/eye mode

How to pervert?

Kernel mode->User mode

A privileged instruction that modifies PSW

User mode->Kernel mode

Caused by an interrupt, the hardware automatically completes

example

system call

An interrupt occurred

An error condition occurred in the user program

Attempt to execute a privileged instruction in user program

The transition from the core state to the user state is implemented by an instruction. This instruction is also a privileged command, usually an interrupt return instruction.

Kernel (the underlying software configured on your computer) The most important and core part of the operating system

clock management

Implement timing function

Interrupt mechanism

Responsible for implementing the interrupt mechanism

primitive

is a special program

It is at the bottom of the operating system and is the part closest to the hardware.

The operation of this kind of program is atomic - its operation can only be completed in one go and cannot be interrupted.

Short running time and frequent calls

Data structure and processing of system control Functions to manage system resources

Process management

memory management

Device management

interrupt

The role of interrupts

Let the operating system kernel forcibly take back control of the CPU

Change the CPU from user mode to kernel mode

Classification of interrupts

Internal interrupt (exception/exception/trap) Relevant to the currently executed instruction The interrupt signal comes from inside the CPU

trap, fall into

Trapped in instruction raise, application intentionally raises

Fault

Caused by an error condition that may be fixed by a kernel program. After the kernel program is repaired, the CPU usage rights will be returned to the application, allowing it to continue executing. (such as page fault interrupt)

termination

Caused by a fatal error, the kernel program cannot repair the error and generally terminates the application directly. (such as integer division by zero, illegal use of privileged instructions)

External interrupt (narrow sense interrupt) Regardless of the currently executing instruction The interrupt signal comes from outside the CPU

Peripheral request (clock interrupt)

Human intervention (I/O interrupt request)

The basic implementation principle of the interrupt mechanism

Check interrupt signal

Internal interrupt: The CPU checks whether an exception occurs when executing instructions

External interrupt: At the end of each instruction cycle, the CPU checks whether there is an external interrupt signal that needs to be processed.

Find the corresponding interrupt routine

"Interrupt vector table"

System call (interface provided by the OS to applications/programmers) Program interface/generalized instructions

System calls are when users call some sub-functions provided by the OS in a program and can be regarded as special public subroutines. Involves system resource management and process management. Certain privileged instructions must be used, so running in core mode

The difference between system calls and library functions

Some library functions further encapsulate system calls.

Some library functions do not use system calls

What functions need to be implemented using system calls?

Device management

File management

process control

process communication

Memory management

System call process

Passing on parameters

Trapped in command/trap/access management

System call requests are processed by the operating system kernel program

Return to application

Architecture

big core

The main functional modules of the operating system are used as the system kernel and run in the core state.

Advantages: high performance

Disadvantages: The kernel code is huge, confusing structure, and difficult to maintain

microkernel

Keep only the most basic functions in the kernel

Advantages: fewer core functions, more reliable, clear structure, easy to maintain

Disadvantages: Frequent switching between core mode and user mode is required, low performance

Interrupts and Exceptions

The difference between interrupt handling and subroutine calling

Entrance address

interrupt

Obtained from the interrupt implicit instruction according to the interrupt vector

subroutine call

Obtained by the calling program according to the addressing mode

save environment

interrupt

Save PC, PSW, general register

subroutine call

Save PC, General Purpose Register

process status

interrupt

From user mode to kernel mode

subroutine call

No state changes

Parallelism vs. Concurrency

OS concurrency is achieved through time sharing

Concurrency

Two or more events occur within the same time interval

Parallelism

Two or more events are sent at the same time

Requires hardware support

In a multiprogramming environment, over a period of time, macroscopically, multiple programs are executed simultaneously At a certain moment, only one program is actually executed in a single-processor environment. Microscopically, the programs are executed alternately in a time-sharing manner.