1: Computer operating system goals and functions
- Goal: convenient, effective, extensible, open
a: convenient: easy to use
b: effective: resource utilization, usable and programmable
c: expansion: adding new modules and functions
d: open: standard, software and hardware compatible - Functions:
a: os as the interface of computer hardware
b: os as the manager of computer system resources (processor, memory, io, files)
c: os realizes the abstraction of computer resources (bare metal, abstraction, software, user-friendly ) - Power
a: Utilization
b: User convenience
c: Device update
d: Computer architecture evolution
e: New requirements
2: The development process of computer systems
- Computer system without operating system
a: manual operation
Disadvantage: user exclusive, cpu waiting for manual operation (utilization, human-machine contradiction, slow io)
b: introduction of offline input and output
peripheral input machine (reduces cpu idle, improves io ) - Single-channel batch system
A batch of jobs are all introduced, supervised by the supervisory program, and executed one by one.
Disadvantages, cpu waits for i/o, waste is serious - Multi-channel batch processing system
Multiple programs are executed at the same time, and CPU is requested according to job requirements, so that the CPU is always in a busy state
Advantages and disadvantages :
a: high resource utilization
b: high system throughput
c: long average turnaround time
d: no interaction capability
Problems to be solved :
a: processor contention
b: memory allocation and protection
c: io device allocation
d: file organization and management
e: job management
f: user and system interface problems - Time- sharing system
introduction : human-computer interaction, shared host
Problems
: a: Timely reception
b: Timely processing (1: Job directly into memory 2: Polling operation (time slice))
Feature
a: Multiplexing: multi-user sharing
b: Independence: mutual non-interference
c: timeliness: 1~3s
d: interactivity: man-machine dialogue - Real-time system
Real-time system type
a: Industrial weapon control system
b: Information query system
c: Multimedia system
d: Embedded system
Real-time
task type a: Periodic real-time task and aperiodic real-time task [start deadline, completion deadline]
b : Hard real-time and soft real-time tasks Comparison of
real-time
systems and time-sharing systems a: Multiplexing
b: Independence
c: Timeliness
d: Interactivity
e: Reliability - Microcomputer operating system
single-user single-task operating system
a: CP/M
b: MS-DOS
single-user multi-task operating system
windows series
Remarks : Single-user multi-task operating system means: a computer can only be used by one user at the same time, but This user can run or submit multiple jobs at a time. For example: Windows, although Windows 2000 and XP can have multiple users, why is it still a single user? Because Windows can set up multiple users, but at the same time, only one user can exclusively share all the resources of the system, so windows is a single user. User operating system. Because the definition of "multi-user" is to allow multiple users to use the same host through their respective terminals to share various resources of the host system (eg, UNIX, Linux, etc.).
Multi-user multi-tasking operating system
a: UNIX OS
b: Solaris OS
c: Linux OS
3: Basic characteristics of computer operating systems
- Concurrency
Parallelism and Concurrency
Parallelism: Two or more events occur at the same time
Concurrency
:
Two or more events occur at the same time interval data, stack, etc.) - Shared
Mutually Exclusive Sharing
Printer, tape drive: Only one process can access the resource at a specified time
Critical resource:
Simultaneous access
to most physical resources, stacks, variables, and tables in the system Simultaneous: Macroscopically, alternately executed at the microscopic level
Disk configuration, reconfiguration code written in the file. - Virtual
time division multiplexing
a: virtual processor technology
The time division multiplexing method enables the processor to serve multiple processes in different time slices, and the end user does not feel it
b: The virtual configuration technology
time division multiplexing method turns io devices, etc. into logic On multiple machines
Spatial division multiplexing
frequency band : One channel becomes many channels
Replacement : 100MB application program is replaced in 30MB memory space - Asynchronous
stop and go, allocate processors, io and other equipment according to needs, and finally complete a certain program
4: The main functions of the computer operating system
- Processor management
a: process control (create a cancel process for jobs, process running state transition)
b: process synchronization [multiple processes or thread coordination (1: process mutual exclusion: access to critical resources. 2: process synchronization: coordination, cooperation , critical resource lock W)]
c: Process communication
Direct communication, the original process hangs the message on the message queue of the target process, and the target process uses the receive command to take out the message from the message queue
d: Scheduling
a: Job scheduling : allocate resources, establish Process, get the processor ready process, insert the ready queue
b: process scheduling : select the process, assign the processor, set the running site, put into execution - Storage management
Memory allocation
a: Programs get their own way b
: Improve memory utilization and reduce memory fragmentation c: Add memory
(static, dynamic) to running programs The user program is not allowed to access the programs and data of the operating system, and the user program is not allowed to be transferred to other non-shared user programs for execution Address mapping Logical addresses correspond to physical memory addresses Memory expansion Request call-in, replacement function
Device Management
Buffer Management
Set up buffers between io devices and CPUs to improve CPU utilization and system throughput
Device
allocation Allocate existing resources according to user needs
Device processingFile managementFile
storage space managementDirectory
managementFile read-
write management and protection- interface between the operating system and the user
user interface
program interface - Modern Operating Systems New Features
System Security
Network Features and Services
Support Multimedia