operating system
Modern computer systems are composed of one or more processors, main memory, printers, keyboards, mice, monitors, network interfaces, and various input/output devices.
However, programmers will not directly deal with these hardware, and it is impossible for each programmer to master all the details of the computer system, so we don’t have to write code anymore, so on the basis of the hardware, the computer is installed with--layer Software, this layer of software can achieve the effect of controlling the hardware by responding to the instructions input by the user, thereby meeting user needs. This kind of software is called an operating system. Its task is to provide a better, simpler and clearer for user programs. Computer model.
Our common operating systems are mainly Windows, Linux, FreeBSD or OSX. This kind of operating system with a graphical interface is called Graphical User Interface (GUI), and the text-based and command-line-based operating system is usually called Shell . Below are the components of the operating system we are going to explore
This is a simplified diagram of an operating system. The bottom part is the hardware. The hardware includes the devices we mentioned above, such as chips, circuit boards, disks, keyboards, and monitors. Above the hardware is software. Most computers have two operating modes: kernel mode and user mode. The most basic part of the software is the operating system. It runs in the kernel mode. The kernel mode is also called the tube mode and the core mode. They are both operating systems. State is just a different name. The operating system has access to the hardware and can execute any instructions that the machine can run. The rest of the software runs in user mode.
User interface programs (shell or GUI) are in user mode, and they are located at the lowest level of user mode, allowing users to run other programs, such as web browsers, email readers, music players, etc. Moreover, the closer you are to the user mode, the easier it is to write an application. If you don’t like a certain email reader, you can rewrite it-one or another, but you cannot write an operating system or an interrupt handler by yourself. This program is protected by hardware to prevent external modifications to it.
First look at the overall context of this note
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Know the operating system
operating system
Introduction to Computer Hardware
Operating System Museum
Operating system concept
System call
Operating system structure
Processes and threads
process
Thread
Interprocess communication
Scheduling
RAM
No memory abstraction
A memory abstraction: address space
Virtual Memory
Page replacement algorithm
File system
file
table of Contents
File system implementation
File system management and optimization
I / O
I/O device
I/O software principle
I/O hierarchy
plate
clock
Deadlock
Resources
Deadlock
Bei ostrich algorithm
Deadlock detection and recovery
Deadlock avoidance
Destroy deadlock
other problems
to sum up
Operating system interview questions
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