Reference:
https://en.cppreference.com/w/cpp

https://www.runoob.com/cplusplus/cpp-constants-literals.html

Main() function

#include<iostream>

void main()
{
    std::cout << "Is there a bug here?";
}

Error:
||=== Build: Debug in C++practice1 (compiler: GNU GCC Compiler) ===|
\C++practice1\main.cpp|3|error: ‘::main’ must return ‘int’|

C/C++ 11 standard regulate that main() must be int type. Only in this case, operation system will know whether the program runs successfully.
main()必须为int类型并且有返回值，自定义函数可为void类型无返回值。

The correct program should be:

#include<iostream>

int main()
{
    std::cout << "Is there a bug here?";
    return 0;
}

Console input/output

# include <iostream>

using namespace std;

int ConsoleOutput()
{
    cout << "This is a console print and read test:" << endl;
    cout << "Pi when approximated is 22/7 = " << 22/7 << endl;
    cout << "The actual Pi value is 22/7 = " << 22.0/7 << endl;
    cout << "Please input a integer: ";
    int InNum;
    cin >> InNum;
    cout << "The gust entered number " << InNum <<endl;
    return 0;
}

int main()
{
    cout << "Hello world!" << endl;
    return ConsoleOutput();
}

output:
Hello world!

This is a console print and read test:

Pi when approximated is 22/7 = 3

The actual Pi value is 22/7 = 3.14286

Please input a integer: 10

The gust entered number 10