The United States Postal Service (USPS) delivers millions of pieces of mail each day. Much of the sorting and distribution process is done quickly and efficiently through the use of bar codes. As each piece of mail arrives at the processing center, it is passed through an optical character reader (OCR), which translates and prints the ZIP Code as a bar code onto the lower right corner of the envelope. Bar code sorters (BCS) then read the code and direct the mail to its destination.