int ascii_to_radix40(Radix40 *radix40_data, unsigned char *ascii_data, int max_chars)
/* this routine converts a null-terminated ascii character string */
/* to radix 40 representation.  The allowable characters are: */
/* A-Z, 0-9, period, comma, hyphen, and space.  If any illegal characters */
/* are detected, they will be converted to hyphens, and the return value */
/* will be S_ILLEGAL. */
/* Lowercase letters will be upper-cased without error indication. */
/* The radix40 value will be padded with blanks to a multiple of three */
/* characters. If the number of characters in the ascii string is > max_chars */
/* only max_chars will be converted, and the return value will be S_ILLEGAL. */
/* If no error is detected, the return value will be S_OKAY. */
{
	int i;
	unsigned char j;
	int ascii_length;
	int result;
	int words_to_convert;
	int words_to_clear;
	int cycle;
	unsigned current_word_index;

	result = S_OKAY;
	ascii_length = strlen((char *)ascii_data);
	if (ascii_length > max_chars)
		{
		ascii_length = max_chars;
		result = S_ILLEGAL;
		}

	words_to_convert = ascii_length / 3;
	if (ascii_length % 3 != 0)
		words_to_convert ++;

	words_to_clear = max_chars / 3;
	if (max_chars % 3 != 0)
		words_to_clear ++;

	memset(radix40_data,0,words_to_clear*sizeof(Radix40));

	current_word_index = unsigned(-1);
	cycle = 0;
	for (i = 0; i < ascii_length; i ++)
		{
		if (cycle == 0)
			current_word_index ++;
		j = lookup_chars[ascii_data[i]];
		if (j & ILLEGAL)
			{
			j = HYPHEN ; /* make it a hyphen */
			result = S_ILLEGAL; /* and remember that it was illegal */
			}
		radix40_data[current_word_index] += weights[cycle] * j;
		cycle = (cycle + 1) % 3;
		}

	return(result);
}