01  #include <stdio.h>
02  
03  int main()
04  {
05   long decimal;
06   int remainder;
07   long octal = 0, i = 1;
08   printf("Enter a decimal numbern");
09   scanf("%ld", &decimal);
10  
11   while(decimal != 0)
12   {
13    remainder = decimal%8;
14    octal = octal + (remainder*i);
15    decimal = decimal/8;
16    i = i*10;
17   }
18   
19   printf("Octal number : %ld", octal);
20  
21  return 0;
22  }

 OUTPUT :
 
 Enter a decimal number : 100
 Octal number : 144