One type of card OS is the most cost- effective in many businesses because you only pay for the size and functions that you specify. This Classic approach treats each card as a secure computing and storage device. Files and permissions to these files are all set by the issuer in advance. The only access to the cards is through the operating system. There are no back doors, no reconfiguration of file structures on the card.
Data is read or written to the card through permissions set only by the issuers.
The CardLogix M.O.S.T. OS is one example of this type. The second methodology is the Disk Drive approach to card operating systems. The card operating system allows for active file allocation and management. Java Cards and the Microsoft Windows Card OS are examples of this approach. These cards have a much higher risk of tampering due to the ability to introduce active applets and or viruses into the card.