Its very simple. You can achieve this by using bit wise operator.

Have a look.

Input :

```
int16_t num = 127; // bit representation of 127 (0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1)
num = (num << 8 | num >> 8); //This is what you need to do. This will swap the 0-7th bit to 8-15th bit
/*
If you print the bit of "num" after applying the left shift (<<) and right shift (>>) operation you will get the
following output.
*/
(0 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0)
```

Here the program for that, (Tested):

```
#include <stdio.h>
#include <stdint.h> // For int16_t
/*
Function to print the bits of the given number.
*/
void show_bit(int16_t n)
{
int i = 16;
while(i)
(n >> (i-- - 1) & 1) ? printf("1 ") : printf("0 ");
printf("\n");
}
int main()
{
int16_t number = 127; // You can change the number as per your requirement.
printf("Before swaping the bits of (%d) :\n", number);
show_bit(number);
number = (number << 8 | number >> 8);
printf("After swaping the bits of (%d) :\n", number);
show_bit(number);
return 0;
}
```

Output:

```
Before swaping the bits of (127) :
0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1
After swaping the bits of (32512) :
0 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0
```