In order to facilitate bar coding of inventory items, stock numbers between 1 and 9999999 are reserved for the bar coding system. This is done because a stock number can consist of any combination of 20 characters and numbers that either cannot be reproduced by a bar code or would produce a bar code too long to physically fit on a printed label of reasonable size. In order to allow for 20-character alpha numeric stocks numbers but also have a unique bar code for each stock number, the system assigns a unique bar code number to each stock item. These unique bar codes are numbers between 1 and 9999999. Therefore, a stock item cannot be entered with all digits within this range or the system would not be able to reliably look up a stock number by its bar code.