Exchange the bits at even and odd positions

Write code to exchange the bits at even and odd positions in a number.

Answer:

/**
 * Program to exchange the bits at even and odd positions
 * */
#include "stdio.h"
#include "stdlib.h"

void PrintBinary(size_t num)
{
    for( int i = 31; i >=0; --i )
        if ( num & ( 1 << i) )
            printf("1");
        else
            printf("0");
    printf("\n");
}

size_t SwapBits(size_t num)
{
    /* Program to reverse the bits of a number */

    return ( (num << 1) & 0xAAAAAAAA ) |
        ( (num >> 1 & 0x55555555) );
}

int main(int argc, char* argv[])
{
    for ( int i = 1; i <= argc-1; ++i )
    {
        size_t num = atoi(argv[i]);
        PrintBinary(num);
        PrintBinary(SwapBits(num));
    }
    return 0;

}