JavaCard OS

Recently, I am always thinking about one problem: how does a real java card executes APDU based on the cap file?
When we sent APDU command to the card, how does card treats the command and cap file? Anyone knows?

Just think of the cap file as a JAR file and it contains the byte code for your applets. When the CAP file is loaded and installed, the JCVM parses certain tokens out that enable it to execute.