Operating System 1 - Overview

1. Bare Metal: A computer without any software support is called bare metal.
2. Virtual machine: Through the resource functions provided by Os and various user-friendly service functions, the bare metal is transformed into a machine with stronger functions and more convenient use, which is usually called a virtual machine or an extended machine.
3. Channel: It is a special processing component that can control the work of one or more I/O devices and is responsible for the information transmission between I/O devices and main memory.
4. Four states of a batch job: Submit, Contain, Execute, Complete.
5. Batch OS features:
   1) Users use the computer offline
   2) Batch processing
   3) Multi-program running
   Disadvantages: No interactivity
6. Time-sharing system features:
   1) Interactivity
   2) Multi-user simultaneity
   3) Independence
7. The main characteristics of real-time systems are: to provide immediate response and high reliability