Learn C++ from scratch, multiplication table

This code is written in C++ and it prints the relationship between the numbers 1 to 9 and their product. Specifically, it uses two nested for loops to iterate over each pair of numbers (i,j), where i goes from 1 to 9 and j goes from 1 to i. For each pair of numbers, the code will print out the product of j and i, separated by "*".

The following are comments explaining the code:

#include <iostream>  // 包含输入输出流库  
  
int main() {         // 主函数  
  
    for (int i = 1; i <= 9; i++) { // 外层循环，i从1到9  
        for (int j = 1; j <= i; j++) { // 内层循环，j从1到i  
            cout << j << "*" << i << " = " << j * i << " "; // 打印j和i的乘积，中间用"*"隔开  
        }  
        cout << endl; // 换行，下一行输出  
    }  
  
    return 0; // 主函数返回0，表示程序正常结束  
}

The output of this code is as follows:

1*1 = 1   
1*2 = 2 2*2 = 4   
1*3 = 3 2*3 = 6 3*3 = 9   
1*4 = 4 2*4 = 8 3*4 = 12 4*4 = 16   
1*5 = 5 2*5 = 10 3*5 = 15 4*5 = 20 5*5 = 25   
1*6 = 6 2*6 = 12 3*6 = 18 4*6 = 24 5*6 = 30 6*6 = 36   
1*7 = 7 2*7 = 14 3*7 = 21 4*7 = 28 5*7 = 35 6*7 = 42 7*7 = 49   
1*8 = 8 2*8 = 16 3*8 = 24 4*8 = 32 5*8 = 40 6*8 = 48 7*8 = 56 8*8 = 64   
1*9 = 9 2*9 = 18 3*9 = 27 4*9 = 36 5*9 = 45 6*9 = 54 7*9 = 63 8*9 = 72 9*9 = 81