The multiplication from the older discharge with a shift to the left

Question

Hello everybody! Such a problem: it is necessary to realize the multiplication from the older discharge with a shift to the left.

Here is the part of the code where I "realized" it, but the program displays the wrong result. Tell me where the mistake is, please...

My code:

........

int result;

for (int n=sizeof(int)*2; n; n--){

  if ((b>>(n-1))&0x01){

  int c=a&a, d=a^a, e;                      

while(c^(e=c|((c<<1)&d))){               

c=e;    

}                                            

result=(c<<1)^d;    

    result=result<<1;

    result=result+a;

    }else       {

  result=result<<1;

}

  }

  cout<<"##########\n"<<result<<endl;

.........