The side effect is to output the right hand variable and the expression produces a value that is an output stream (technically its a reference to an output stream, but it amounts to the same thing). This value can be used again as the left hand size of a <<. So to call the put functions 3 times as before:-

cout << "x = " << x << "\n";

because the << operator is evaluated left to right. It take a little getting used to for a FORTRAN programmer, but after a while you get used to seeing this as a cout object with a stream of values flowing into it.

As you might expect, input simply reverses the sign on the flow, so to read 3 numbers from the input stream and store them in x, y, z:-

cin >> x >> y >> z;

其实可以形象地来理解这个问题，你可以把箭头的方向看作是数据流动的方向

比如，>>就是数据从左侧流动到右侧，也就是从左侧流出，那么在输入输出过程中，cin或者cout位于我们的左侧，而只有cin是流出（从键盘流出），cout是流入（流入到屏幕）

那么很自然的就是

int n;

cin>>n; // 数据从键盘流入变量n

cout<<n;// 变量n的数据流入到屏幕

这样记忆就很容易了

很抱歉回答晚了，希望可以帮助到你