01  #include <stdio.h>
02  
03  int main()
04  {
05   long binary;
06   int remainder;
07   long decimal = 0, octal = 0, i = 1;
08  
09   printf("Enter a binary number : ");
10   scanf("%ld", &binary);
11  
12  
13  /* Convert Binary to Decimal number first */
14  
15  
16   while(binary != 0)
17   {
18    remainder = binary % 10;
19    decimal = decimal + (remainder * i);
20    binary = binary / 10;
21    i = i * 2;
22   }
23  
24  /*Then convert decimal to octal number */
25  
26   i = 1;
27  
28   while(decimal != 0)
29   {
30    remainder = decimal%8;
31    octal = octal + (remainder*i);
32    decimal = decimal/8;
33    i = i*10;
34   }
35  
36  printf("Octal number : %d", octal);
37  
38  return 0;
39  }

 OUTPUT :
 
 Enter a Binary Number : 1010
 Octal number : 12