Common operating systems:
For example: MacOS, ios, Windows, Android
The concept of operating system (OS):
Control and manage the hardware and software resources of the entire computer , and rationally organize and schedule computer work and resource allocation;
Provide convenient interfaces and environments for users and other software ;
It is the most basic system software in the computer system .
Operating system functions and goals
System resource manager
Functions: Processor (CPU) management, memory management, file management, device management
Goal: safe and efficient.
Execute the program: Put the program into memory --> be processed by the CPU
Provide convenient and easy-to-use services to upper levels
Encapsulation idea: The operating system encapsulates some ugly hardware functions into simple and easy-to-use services, so that users can use the computer more conveniently . Users do not need to care about the principles of the underlying hardware and only need to issue commands to the operating system.
GUI: Graphical user interface
Users can operate using an intuitive graphical interface and no longer need to memorize complex commands and parameters.
Early Operating Systems: Command Interface
Online command interface example (Windows system) Online command interface = interactive command interface (processing commands one by one)
Offline command interface example (Windows system) Offline command interface = batch command interface (a bunch of processing commands)
Program interface: You can use the program interface by making system calls in the program. Ordinary users cannot use the program interface directly and can only use it indirectly through program code. (For example: Programmer-->C language library function-->Program interface (system call)-->Hardware)
As the level closest to the hardware
It is necessary to realize the expansion of hardware machines.
A computer without any software support is called a bare metal computer. The operating system installed on the bare metal can provide resource management functions and user-friendly service functions , transforming the bare metal into one with stronger functions and more convenient use.
The machine covered by the software is called an extended machine or a virtual machine.