Don't understand what's wrong

hi

Code:

---

#include <iostream>
using namespace std;
int main()
{ 
    int a,b;
    for(a=10;a<21;a++){
                      b=0;
                      while(a>0){
                                b=b*10+a;
                                a=a/10;
                                }   
                      cout<<b<<endl;
                      }   
    system("pause");
}

---

I have this program.When I run is shows only 111111111111...
why?
normally must output 1,21,31,41,51,61,71,81,91,2 no?

thx

go through the program in your head or on paper, carefully following the steps. write down the values of a and b at every step. you will find the problem.

A second hint. What is the value of anything multiplied by zero?

You are trying to use a as a loop counter, at the same time setting it to 0 inside the loop.