- 1. We usually browse the web apps,
- 2. There are two states when the operating system runs: one is kernel mode and the other is user mode. When you open a file or play a sound, or output a character on the display screen, both of them are actually calling things in the kernel of the operating system. If we compute a 1+2, we’re actually running in user state; How does the operating system work? Through the operating system to call the relevant operating system provided to our API and then run, the common web page is through JS to call the interface that the web browser can provide, and then to render the web page, such as open the page to listen to songs, watch movies and a series of operations; The relationship between an application and an operating system is like that between a web page and a browser
- 3. What exactly is a browser? The most important interface for users to access the Internet is the browser as a piece of software
Navigator. UserAgent (browser userAgent, can output browser kernel, relevant version number)
Check whether it is a mobile terminal (Open the Mobile terminal of Taobao, and you can switch the model through the mobile terminal to obtain whether the mobile operating system is Android or iPhone)
Identifies the H5 container to facilitate calls to H5 container-specific interfaces
- Do WeChat ordinary time, is to determine the WeChat call, we can use a simple way to use the user-agent to identity, this thing is from WeChat, we sent out to the WeChat interface, and the web interface has a slightly different, may want to take a slightly letter related js, usual do WeChat development, same page can be either on the web Pages can be put into wechat, at this time we need to use some user agents, sent by the wechat client to the wechat server
Kernel (the core of the operating system)
System call (that is, when we switch from user mode to kernel mode, it is called trap in programming, simply called system call, kernel code is simple and efficient, basically no bug)
To invoke the services provided by the operating system (we look at a web page is called jpu graphics display, is actually a web browser calls, browser calls the browser kernel, browser kernel rendering engine, the last call or system calls, file calls, gpu calls, voice calls as well as the hardware calls)
HTTP is built on top of TCP, and the connection we set up is actually a TCP connection
