Abstract: An operand stack (10) permits optimization of memory space and a continuous check of operand type by creating a type memory (20) which stores type information for each operand, said information comprising information about the length of the operand. This length information available for each single operand permits the operands to be stored extremely densely, while the prior art uses uniform length stack elements for each operand, their length depending on the longest operand.

Abstract: A method is proposed for operating a portable data carrier designed for executing reloadable function programs. According to the method the data carrier initially has installed thereon a loader interface which allows the reloading of load applications which in turn permit the loading of function programs. Each load application has allotted thereto an invariable assigned address space. To support the management of an assigned address space, badges are produced for application programs to be reloaded, said badges containing information about the size of the memory space required for the application program. Address space in the memory device is allotted to application programs to be reloaded in accordance with the size information provided on the badges. A data carrier suitable for carrying out said method is further disclosed.

Abstract: A method is proposed for virtual enlargement of the stack of a portable data carrier allowing reloading of executable program code. To permit the execution of programs requiring a larger stack than that physically present, the stack is segmented into at least two stack segments and their fill state monitored. When complete occupation of a segment is recognized, the oldest stack segment is swapped out to a further storage medium. The further storage medium is a nonvolatile read-write memory that can be a slower memory compared to the stack. When sufficient memory space is available in the stack again, the swapped out segment is returned. The method includes managing a destination address of each stack segment swapped out to the non-volatile read-write memory in a register in a volatile read-write memory.

Abstract: A data carrier for interpreter-based execution of an application existing in the form of an application program resulting from an object-oriented source program includes a communication device (10), and a memory device (12) containing at least one application program and an interpreter unit (15). The application program is structured in class files (22) each containing a library section (25) whose entries (46) are formed by invariable elements of the interaction context and which is structured in a sequence of equally long segments (50) each comprising a predetermined number of bytes. A certain number of segments (5) forms an entry (46). The physical position of the first segment of each entry (46) within the byte sequence is used by the interpreter unit (15) as a reference for the entry (46).

Abstract: A method is proposed for virtual enlargement of the stack of a portable data carrier (10) allowing reloading of executable program code. To permit the execution of programs requiring a larger stack than that physically present, the stack (26) is segmented into at least two stack segments (30) and their fill state monitored. When complete occupation of a segment (30) is recognized, the oldest stack segment (30) is swapped out to a further storage medium (18). The further storage medium (18) can be a slower memory compared to the stack (26). When sufficient memory space is available in the stack (26) again, the swapped out segment (30) is returned.

Abstract: A data carrier is proposed for interpreter-based execution of an application existing in the form of an application program resulting from an object-oriented source program. The data carrier comprises a communication device (11) for exchanging data with an external unit, a processor device (10), and a memory device (12) containing at least one application program and an interpreter unit (15). The application program is structured in class files (22) each containing a library section (25) whose entries (46) are formed by invariable elements of the interaction context and which is structured in a sequence of equally long segments (50) each comprising a predetermined number of bytes. A certain number of segments (50) forms an entry (46). The physical position of the first segment of each entry (46) within the byte sequence is used by the interpreter unit (15) as a reference for the entry (46).