/* Midterm practice #3.  Implement the following function according to
 * the specification.  Follow the C-assembly interface conventions of
 * the lab's compiler and assembler.
 *
 * In:  source - the source string
 *      dest - the destination memory to which the string should be copied
 *      n - the size of the destination region
 * Out: -1 - if nbytes is not sufficient
 *       0 - if the copy was successful
 * Recall that C strings are terminated with a 0.  This function copies
 * a C-string to a given memory region, stopping (successfully) after
 * copying the null terminator and returning 0, or (unsuccessfully) after
 * nbytes bytes have been copied without encountering a null terminator
 * and returning -1.
 */
short copy_string(char * source, char * dest, unsigned short nbytes);