There are predominately two styles of Card Operating Systems. The 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 is 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 issuer.
The operating system performs a set of applications such as authentication and encryption as requested through commands sent to the card. This type of card is the most cost effective in many business settings because you only pay for the size and functions that you specify. The M.O.S.T. Card Family from CardLogix and the FIPS2000 system are products in this Style. The second methodology is the Disk Drive approach to card operating systems. The OS has an active memory manager, this allows you to load onto the card specific applications and files.