Equations for SCC and UPC codes
You can use existing equation functions to construct 
		SCC, 
		UPC and other types of codes. These codes are strings of
		numbers that typically include a check digit, based on the other digits in the
		code. The check digit is based on an algorithm that you construct. 
	 
Two examples, 
		EQ_SCC and 
		EQ_UPC, are in the seed database. These equations define
		an informational parameter.