#include <stdio.h>
#include <stdlib.h>

unsigned int TestF( unsigned char a,
                    unsigned char b,
                    unsigned char c,
                    unsigned char d )
{
    return ( a << 24 ) | ( b << 16 ) | ( c << 8 ) | d;
}

int main()
{

    unsigned int ret_val = TestF( 1, 2, 3, 4 );

    printf("%08X\n", ret_val);

    return 0;
}

/*
output:

01020304
*/