01  #include<stdio.h>
02  #define MAX 1000
03  
04  int main()
05  {
06   char octalNumber[MAX];
07   long int i=0;
08  
09   printf("Enter any Octal number : ");
10   scanf("%s",octalNumber);
11  
12   printf("Binary value : ");
13  
14   while(octalNumber[i])
15   {
16    switch(octalNumber[i])
17    {
18    case '0': printf("000"); break;
19    case '1': printf("001"); break;
20    case '2': printf("010"); break;
21    case '3': printf("011"); break;
22    case '4': printf("100"); break;
23    case '5': printf("101"); break;
24    case '6': printf("110"); break;
25    case '7': printf("111"); break;
26    default:  printf("nInvalid octal digit %c ",octalNumber[i]); return ;
27    }//end of switch
28  
29    i++;
30  
31   }//end of loop
32  
33  return 0;
34  }

 
 OUTPUT :
 
 Enter any Octal number : 12
 Binary value : 001010