当用户进行系统调用陷入内核态的时候，特权级别发生变化，因此也需要切换堆栈，内核空间使用的就是内核栈.
将fork()和exec()进行分离，能够在创建子进程之后、运行子进程程序之前运行其他代码，从而能够灵活地进行设置，改变子进程程序的运行环境。wait()函数则提供了在进程运行顺序不确定的情况下，保证子进程优先运行的一种方法。
父进程与子进程的变量相互独立.
使用pipe进行进程间通信.
wait()函数返回子进程pid.如果错误返回(pid_t)-1.
如果一个进程没有子进程，那么wait()返回-1,并且errno设为ECHILD.
子进程不会产生任何输出。
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
An Open Source Machine Learning Framework for Everyone
Django
The Web framework for perfectionists with deadlines.
Laravel
A PHP framework for web artisans
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
Some thing interesting about web. New door for the world.
A server is a program made to process requests and deliver data to clients.
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
Some thing interesting about visualization, use data art
Some thing interesting about game, make everyone happy.
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
Microsoft
Open source projects and samples from Microsoft.
Google
Google ❤️ Open Source for everyone.
Alibaba
Alibaba Open Source for everyone
D3
Data-Driven Documents codes.
Tencent
China tencent open source team.
