How to obtain bit mask between two bit positions?

 int main(int argc, char *argv[])

 {

   unsigned int number;

   unsigned int size;

   unsigned int mask;

   unsigned int pos;

   printf ("Enter the number : ");

   scanf ("%x", &number);

   printf ("Enter position (0-31): ");

   scanf ("%d", &pos);

   printf ("Enter mask size (1-%d): ", 32-pos);

   scanf ("%d", &size);

   printf ("Number : ");

   print_bits(number);

   if(size == 32) {

     mask = 0xFFFFFFFF;

   } else {

     mask = (1 << (size + 1)) - 1;

   }

   number = (number &  (mask << pos)) >> pos;

   printf ("\nBits   : ");

   print_bits(number);

   return 0;

 }

Output

Enter the number : 55AA55AA55
Enter position (0-31): 3
Enter mask size (1-29): 10
Number : 10101010010101011010101001010101
Bits   : 00000000000000000000010101001010


Number : 10101010010101011010101001010101
Bits   :                ==>10101001010<==

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