Operating system (01) - Introduction
Operating System is configured on the computer hardwareFirst layer of softwareIt is the first expansion of the system hardware
Operating system refers to the control and management of the entire computer system and software resources, and rational organization of work and resource allocation scheduling computer to provide convenience to users and other software interfaces and environment collection procedures
main role:
- Management computer systems and software resources
- Rational organization and scheduling of the computer work and allocation of resources to improve their utilization and system throughput
- Provide some simple for the user and application interfaces and environment
Objectives and role
OS target
- Convenience
- Effectiveness
- Improving system resource utilization
- Improve system throughput
- Scalability
- Openness
OS role
As an interface between the user and the computer hardware system
As a manager of computer system resources
- Processor Management: distribution and control processor
- Memory Management: memory allocation and recovery
- I / O device management: assign I / O devices (recovering) the actuating
- File management: file access, sharing and protection
Realized the abstraction of computer resources
The main driving force of the development of OS
Increasing the utilization of computer resources
User-friendly
Constantly upgrading the device
Development of computer architecture
# 单处理机系统发展为多处理机系统，相应的，操作系统也就由单处理机 OS 发展为多处理 OS。 # 当出现了计算机网络后，配置在计算机网络上的网络操作系统应运而生，它不仅能有效地管理好网络中的共享资源，而且还向用户提供了许多网络服务。We have made new applications
User operating system is used by:
System calls
# OS 提供了一组系统调用，用户可在自己的应用程序中通过相应的系统调用，来实现与操作系统的通信，并取得它的服务。Terminal Command
# 这是指由OS 提供了一组联机命令接口，以允许用户通过键盘输入有关命令来取得操作系统的服务，并控制用户程序的运行。Graphics window
# 这是当前使用最为方便、最为广泛的接口，它允许用户通过屏幕上的窗口和图标来实现与操作系统的通信，并取得它的服务。
The computer system resources Categories: - collection of a variety of hardware and software resources
- Processor
- Memory
- I / O device
- File (data and programs)
development process
No operating system of the computer system
Manual operation
# 缺点 """ 1.用户独占全机 2.CPU等待人工操作 """Offline input / output (Off-Line I / O)
# 优点 """ 1）减少了 CPU 的空闲时间。装带卸带以及将数据从低速 I/O设备送到高速磁带上，都是在脱机情况下进行的，并不占用主机时间，从而有效地减少了 CPU 的空闲时间，缓和了人机矛盾。 2）提高了 I/O 速度。当 CPU 在运行中需要数据时，是直接从高速的磁带上将数据调入内存的，不再是低速 I/O 设备上输入，极大地提高了 I/O 速度，从而缓和了 CPU 和 I/O 设备速度不匹配的矛盾，进一步减少了 CPU 的空闲时间。 """
Single-batch system
Simple Batch Processing System of processing:
Single-batch system wherein:
- Automaticity
- Under favorable circumstances, a number of operations on the tape can be automatically run in sequence one by one, without human intervention.
- Sequential
- Each track on the magnetic tape operations are sequentially into the memory, to complete the job and the order of channels into the sequential memory are exactly the same under normal conditions, i.e., first into memory to complete the operation.
- Single channel of
- Memory, only one program is running, each program that is supervised transferred to a program from the tape into the memory to run only when the program is completed or an exception occurs, it swapped its successor program into the memory to run.
Single-batch system Disadvantages: system resources are not fully utilized
# 因为在内存中仅有一道程序，每逢该程序发出I/O请求后，CPU便处于等待状态，必须在其I/O完成后才能继续运行。
# I/O设备的低速性，更使得CPU的利用率显著降低Multi-batch system
Multiprogrammed Batch Processing System of basic concepts:
# 作业调度程序按一定的算法从后备队列中选择若干个作业调入内存，使它们共享 CPU 和系统中的各种资源- Backlog
- Job Scheduler
- Share CPU and system resources
# I/O操作——》CPU空挡期——》多道程序交替运行——》保持CPU处于忙碌状态Multi-batch system advantages:
- High resource utilization
- CPU utilization: multiprogramming operating alternately
- Memory utilization: memory charged multiprogramming
- I / O utilization
- Large system throughput
- CPU and other resources remain "busy" state
- Only when the job is completed or when the run does not go switching, small system overhead
Batch disadvantage of multi-channel system:
The average turnaround time is long
# 作业的周转时间是指从作业进入系统开始，直至其完成并退出系统为止所经历的时间。在批处理系统中，由于作业要排队，依次进行处理，因而作业的周转时间较长，通常需几个小时，甚至几天。No interactive capabilities
Multi-batch system issues still need to be addressed: To make the system of multi-channel programs can be coordinated operation
- Processor contention
- Memory allocation and protection
- I / O devices Distribution
- Organization and management of documents
- Job Management
- User interface issues with the system
Time-Sharing System
Time Sharing System produces:
Facilitate human - computer interaction
Can be shared host
# 用户们在共享一台计算机时，每个人都希望能像独占时一样，不仅可以随时与计算机交互，而且还不会感觉到其它用户的存在User-friendly machine
Time-sharing system to achieve the key problems:
Received in time
- To promptly receive commands entered by the user, the system simply configure a multi-channel card . Multiple cards can be effect allows the host to receive data input from each user terminal simultaneously.
In time: the key to human-computer interaction, the user is able to control the operation of their own work in a timely manner after typing a command, or to modify their work.
Work directly into memory
Using the rotation operating mode - timeslice
# 系统规定每个作业每次只能运行一个时间片，然后就暂停该作业的运行，并立即调度下一个作业运行
Sharing system features:
Multiple sex
# 允许在一台主机上同时连接多台联机终端，系统按分时原则为每个用户服务。多路性即同时性，它提高了资源利用率，降低了使用费用，从而促进了计算机更广泛的使用。Independence
# 每个用户各占一个终端，彼此独立操作，互不干扰Timeliness
# 用户的请求能在很短时间内获得响应Interactivity
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Real-Time Systems
Real Time System is a system able to respond to requests in a timely manner to external events , complete the processing of the event within the event specified , and control the operation of all real-time tasks coordinated.