How to convert binary number to decimal number using recursion in C

Recursive function:

int binary(int num,int step){
     if(!num){
         return num;
     }
     printf("step %d: binary no=%d,rem=%d \n",step,num,num%10);
     num=num%10+2*binary(num/10,step+1);
     printf("backtrack res step %d (decimal)=%d\n",step,num);
     return num;
 }

the above function recursively calls itself by passing the binary number whose last digit is removed and stored in num%10 (remainder) which will be added and multiplied by two in each phase while backtracking.

     num=num%10+2*binary(num/10,step+1);

the output of the code along with the values of variables in forward and backward stage are given below:

Source Code:

//  https://www.qxcoding.com/ 

//binary to decimal
 include
 int binary(int num,int step){
     if(!num){
         return num;
     }
     printf("step %d: binary no=%d,rem=%d \n",step,num,num%10);
     num=num%10+2*binary(num/10,step+1);
     printf("backtrack res step %d (decimal)=%d\n",step,num);
     return num;
 }
 int main(){
     int b;
     printf("Enter binary number\n");
     scanf("%d",&b);
     printf("decimal=%d \n",binary(b,1));
 }

if any doubts or queries please comment