If an unauthorised user is found to be using the software, the legitimate user can be identified from the code. The vast majority of possible codes are rejected by the software. The software will function only if a potential user enters a valid product code. A software serial number, otherwise called a product key, is usually not embedded in the software, but is assigned to a specific user with a right to use the software. The purpose and application is different. Serial numbers may be used to identify individual physical or intangible objects (for example computer software or the right to play an online multiplayer game). They are valuable in quality control, as once a defect is found in the production of a particular batch of product, the serial number will identify which units are affected. Banknotes and other transferable documents of value bear serial numbers to assist in preventing counterfeiting and tracing stolen ones. Some items with serial numbers are automobiles, electronics, and appliances.
Serial numbers are a deterrent against theft and counterfeit products, as they can be recorded, and stolen or otherwise irregular goods can be identified. Serial numbers identify otherwise identical individual units with many, obvious uses.
