MSI Plessey Barcode, also referred to as Modified Plessey, is a numeric symbology created by MSI Data Corporation, primarily utilized for inventory control in retail settings. It involves marking retail shelves to track and manage inventory effectively. The MSI Plessey Barcode is a continuous and self-checking barcode format that ensures reliable scanning and accurate data capture. It incorporates module checksum situations, which are mechanisms to verify the integrity of the barcode data by calculating and validating specific checksum values within the barcode. The MSI Plessey Barcode is a valuable tool in retail operations, enabling efficient inventory management and facilitating seamless tracking of products on store shelves.