Lecture Notes - Chapter 2 - 输入输出

cin & cout

No comment is needed. The usage is simple!

Notes: always add endl or '\n' to your output.

Notes: formatted output is flavoured.

Caution: \t may be dangerous

iomanip

吐槽：说实话，这玩意为啥要讲，以及为啥要现在讲……

Hard to use. In modern C++, we seldom use iomanip.

Refer to the samples on Input/Output Manipulation when you use, and you are not required to remember all the usage/feature of each function.

Why we say, input and output is stream

Stream is defined to be a sequence(typically, a sequence of chars), and you can only visit a stream through a position indicator.

... ... a b c ... ...
        ^
        the position indicator

use cin >> a, you extract some char at the position indicator and translate it into the type of a.

// input stream
... ... 123 b c ... ...
        ^
        the position indicator

int a; cin >> a; // read the position indicator, and set `a` to 123.

// input stream
... ... 123 b c ... ...
            ^
            the position indicator

use cout << a, you put some char at the position indicator.

// output stream
... ... 
        ^
        the position indicator

int a = 123; cout << a; // put a into output stream.

// output stream
... ... 123 
            ^
            the position indicator

If

内嵌 if：never use in your code.

? : operator

Useful when conditionally initialize one variable:

int maximum = (a > b) ? a : b;
// Instead of
int maximum;
if (a > b) {
  maximum = a;
} else {
  maximum = b;
}