Understanding of C + + program compilation process

When the program is compiled, all pre-processing commands are processed, replacing the specific contents of the header file with the # include command line, and then compiling the program unit as a whole.

using namespace Std; "Use command space Std".

Classes and functions in the C + + standard library are declared in the namespace STD, so if you need to use the C + + standard library in your program (you need to use the # include command line at this point)

The sum of the numbers of a and b,2?????????????

Sum of 2 numbers

#include <iostream>       //preprocessing naming
using namespace std;    //Using the namespace std
int main ()                 //main functions First
{                //Start part of the main function
   
    int a,b,sum;//define variables
    cin >> a>>b;   //Input statement,    cin input Stream object   ">>" is the extract operator, which is used in conjunction with CIN
    //role: Extracting data from input devices such as keyboards is sent to the input stream cin.
   /*
    their combination abbreviation: CIN statement. When executing the CIN statement in the program, a data input from the keyboard
    assigned to integer variable A, the second data entered is assigned to integer variable B.
    */

Sum=a+b; Assignment statements
cout<< "a+b=" <<sum<<endl; Output statement, Endl is a control, action is a newline (end line abbreviation, indicating the end of the bank)
return 0; Returns a value of 0 to the operating system if the program ends normally
/*
123 456
Result of output: a+b=579
*/
}

Understanding of C + + program compilation process