A brief introduction to Java Card Technology
Smart cards represent one of the smallest computing platforms in use day. The memory configuration of a smart card might have on the order of 1K of RAM, 16K of EEPROM, and 24K of ROM. The greatest challenge of Java Card Technology design is to fit Java system software in a smart card while conserving enough space for applications. The solution is to support only a subset of the features of the java language and to apply a split model to implement the Java virtual machine.
The Java Card virtual machine is split into two part: one that runs off-card and the other that runs on-card. Many processing tasks that are not constrained to execute at runtime, such as class loading, bytecode verification, resolution and linking, and optimization, are dedicated to the virtual machine that is running off-card where resources are usually not a concern.
Smart card differs from desktop computers in several ways. In addition to providing Java language support, Java Card technology defines a runtime environment that supports the smart card memory, communication, security, and application execution model. The Java Card runtime environment conforms to the smart card international standard ISO 7816.
The most significant feature of the Java Card runtime environment is that it provides a clear separation between the smart card system and the applications. The runtime environment encapsulates the underlying complexity and details of the smartcard system. Application request system services and resources through a well defined high level programming interface.



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