01  #include<stdio.h>
02  #include<math.h>
03  #include<string.h>
04  
05  int main()
06  {
07   char hex[20],c; int n;
08   int i=0,decimal=0, rem;
09  
10   printf("Enter octal number : ");
11   scanf("%d",&n);
12  
13   /*octal to decimal*/
14  
15   while (n!=0)
16   {
17    rem = n%10;
18    n=n/10;
19    decimal=decimal+rem*pow(8,i);
20    ++i;
21   }
22  
23   /*now decimal to hexdecimal*/
24  
25   i=0;
26  
27   while (decimal!=0)
28   {
29    rem=decimal%16;
30    switch(rem)
31    {
32     case 10:
33     hex[i]='A';
34     break;
35  
36     case 11:
37     hex[i]='B';
38     break;
39  
40     case 12:
41     hex[i]='C';
42     break;
43  
44     case 13:
45     hex[i]='D';
46     break;
47  
48     case 14:
49     hex[i]='E';
50     break;
51  
52     case 15:
53     hex[i]='F';
54     break;
55  
56     default:
57     hex[i]=rem+'0'; // to make char to int
58     break;
59   }
60   ++i;
61   decimal/=16;
62   }
63  
64   hex[i]='';
65  
66   /* reverse the hex string */
67   strrev(hex);
68  
69   printf("Hexadecimal number : %s ",hex);
70  
71   return 0;
72  }

 OUTPUT :
 
 Enter octal number : 232
 Hexadecimal number : 9A