Unsigned short to char array

[Dufresne]

Hi!
I'm trying to assign bits of an unsigned short number to char .
Suppose that we have 2 unsigned short numbers ;

unsigned short num1 = 30 ;
unsigned short num2 = 740 ;

and a char array

char str[4];

What i want it to set bits of str as bits of num1 and num2.

For instance ,
Here , numbers are 16 bits and str is 32 bits.

So what i want is ,
to assign bits of num1 to first 16 bits of str and
to assign bits of num2 to following 16 bits of str.

How can i do it ?

Thanks in advance,

[msram]

The solution actually depends on the byte ordering of the machine architecture. Assuming that the byte ordering is little endian, and that the size of unsigned short is 2 bytes, the following code does what you want:

#include <stdio.h>

int main()
{
    union package
    {
        struct Nums
        {
            unsigned short num1;
            unsigned short num2;
        }nums;
        
        char str1[4];
    };
    
    union package p;
    
    p.nums.num1 = 30u; 
    p.nums.num2 = 740u;
    
    char str[4];
    str[0] = p.str1[1];
    str[1] = p.str1[0];
    str[2] = p.str1[3];
    str[3] = p.str1[2];

    // If the architecture is big endian, p.str1 would contain the required values;
    // so you wouldn't need a separate array and the above 4 assignments in that case.
    
    for(int i=0; i<4; i++)
        printf("%d ", str[i]);

    printf("\n");
    return 0;
}

With the assumptions mentioned above, the output of the program would be:

0 30 2 -28

To know more about little endian and big endian, please see http://en.wikipedia.org/wiki/Endianness

[msram]

If you want a generic method, better convert the numbers into bit strings and make the assignments appropriately.